Histo Lab Flashcards

Question

What are PAX2 and PAX8 and what can they be used for?

Answer 1

PAX2 and PAX8 are transcription factors that are essential for the development of kidney, mullerian, and other organs. They are expressed in normal kidney as well as in most of the renal neoplasms. PAX2 and PAX8 have very similar expression profiles in RCC and in ovarian and endometrial carcinoma. However, PAX8 is also expressed in thyroid follicular cells and thyroid carcinoma, but PAX2 is typically negative in thyroid tumors. This makes them useful for the workup of metastatic RCC.

Answer 2

AMACR is a mitochondrial enzyme mediating the expression of fatty acids and is commonly expressed in normal hepatocytes, the bronchus, and epithelium of the proximal renal tubules. It is a positive tumor marker for prostatic adenocarcinoma. Almost all papillary RCCs are positive for AMACR, but other types of RCC are rarely positive.

Answer 3

TFE3 is a transcription factor that is overexpressed in a group of RCCs with translocation involving Xp11.2. TFEB is a transcription factor that is overexpressed in RCCs with t(6;11)(p21;q12). Cathepsin-K is overexpressed in most TFE3 translocation carcinomas and all TFEB translocation carcinomas.

Answer 4

Uroplakin III, p63, thrombomodulin, and GATA3.

Answer 5

CD57 (an immunostain) is a useful marker for the diagnosis of metanephric adenoma.

Answer 6

Yes. Seminoma cells morphologically and immunophenotypically resemble embryonic germ cells (primordial gonocytes/gonocytes), whereas embryonal carcinoma cells resemble pluripotent stem cells from the inner cell mass of the blastocyst. Both express markers of "stemness", including OCT3/4 (POU5F1) and NANOG. In the current histogenetic model of testicular germ cell tumors, embryonal carcinoma may arise from seminoma through transformation.

Answer 7

AE1/AE3 and CD30 are diffusely positive in embryonal carcinoma and negative (or focally positive) in seminoma. CD117 and podoplanin (D2-40) are diffusely positive in seminoma and negative (or focally positive) in embryonal carcinoma. SOX2 is expressed in the nuclei of embryonal carcinoma but is not expressed in those of seminoma, whereas SOX17 shows nuclear reactivity in seminoma but not in embryonal carcinoma.

Answer 8

The tumor cells express carbonic anhydrase IX (CAIX) in a diffuse, membranous distribution but staining is absent along the luminal borders of the tumor cells (cup-shaped distribution).

Answer 9

Myogenin and MyoD1 stain skeletal muscle.

Answer 10

Solitary fibrous tumors have a unique staining pattern, staining with CD34, CD99, and bcl-2. They typically arise from serosal surfaces. On low power, they are described as having a "patternless pattern", which means something like "nonstoriform-nonherringbone-nonfascicular".

Answer 11

The acid-fast stains are based on the ability of certain organisms to retain the red dye carbol fuchsin despite acidic decolorization. The carbol buchsin stain is a mixture of fuchsin with phenol (carbolic acid). In the Ziehl-Neelsen technique, heat is used to aid penetration of the carbol fuchsin, and a strong acid (3% HCl) is used for decolorization. The Kinyoun technique is a "cold" technique; heat is not applied; instead, a detergent is used to aid penetration of the dye. The Fite technique is a modified acid-fast stain, where a weaker acid such as 1% H2SO4 is applied instead of HCl for decolorization. Bacteria that are not acid-fast by the Ziehl-Neelsen technique, such as Nocardia and M. leprae, may be acid-fast with the Fite technique (cells with a thin capsule, as may be the situation with many rapidly growing strains, are more susceptible to decolorization, so weaker acid will not decolorize as much). Also, the Ziehl-Neelsen technique may be more sensitive than the Kinyoun technique in detecting lightly staining organisms, since the Kinyoun technique may cause easier decolorization.

Answer 12

Mycobacteria, Nocardia, Corynebacteria, Cryptosporidium, Microsporidium, Isospora, Cyclospora, Sarcocystis, Legionella micdadei, Rhodococcus equi, Saccharomyces.

Answer 13

Expression of Hep-Par 1 with negative MOC31 in the appropriate clinical and morphological setting confirms the diagnosis of HCC. Hep-Par 1 has high sensitivity for HCC. Hep-Par 1 is negative in most adenocarcinomas originating in the pancreas, biliary tree, breast and colorectum. Strong expression has been noted in lung and gastroesophageal adenocarcinomas, but is generally accompanied by strong MOC31 expression. Hepatoid adenocarcinomas of the gastrointestinal tract are also positive for Hep-Par 1. If the staining with Hep-Par 1 is weak or absent, but suspicion of HCC persists based on clinical and imaging findings, other markers of hepatocellular differentiation can be sought such as polyclonal CEA (p-CEA) or glypican-3 (GPC-3). p-CEA shows a canalicular pattern of staining, which is considered pathognomonic of HCC. In contrast, most adenocarcinomas show luminal or cytoplasmic pattern of staining with p-CEA. Both Hep-Par 1 and p-CEA have low sensitivity for poorly-differentiated HCC (around 50%). GPC-3 can be helpful in this situation as it has higher sensitivity for poorly-differentiated HCC. MOC31, a cell surface glycoprotein is negative in >90% of HCC, while majority of adenocarcinomas are positive. This antibody along with one or more hepatocellular markers is extremely useful for the diagnosis of HCC.

Answer 14

Normal urothelium: CK20 positivity confined to the umbrella cell layer, CD44 positivity in the basal cell layer, and a weak and patchy p53 nuclear staining. Reactive urothelium: CK20 positivity confined to the umbrella cell layer, positive CD44 staining, weak and patchy p53 nuclear staining. Urothelial CIS: positive for CK20 and p53 in a strong and diffuse fashion, negative for CD44 staining.

Answer 15

Are also called Hansemann macrophages. These cells are modified macrophages found in malakoplakia of the urinary tract. Malakoplakia is the result of an acquired defect in macrophage function causing impairment of bactericidal activity. These large macrophages that are present at sites of infection (von Hansemann cells) exhibit numerous secondary lysosomes containing partially digested organisms. Fusion and calcification of these lysosomes results in the formation Michaelis-Gutmann bodies, considered pathognomonic of malakoplakia. The Michaelis-Gutmann bodies are one or several round basophilic structures measuring between 1µm and 10µm, can be extracytoplasmic or intracytoplasmic, some are laminated, others appear homogeneous, and others have a dense central core with a targetoid appearance. Michaelis–Gutmann bodies demonstrate positivity with PAS stain, von Kossa stain, and sometimes Perls Prussian blue stain.

Answer 16

Histomorphologically, bladder SmCC resembles its counterparts elsewhere in the body. Unlike SmCC of most other organs, however, the sensitivity of conventional neuroendocrine markers (such as synaptophysin, chromogranin A, NSE, and CD56) has been relatively low in bladder SmCC cases. Therefore, the WHO diagnostic criteria allow for the diagnosis of bladder SmCC to be made on morphologic grounds alone. CD56 stains 71% of bladder SmCC, synaptophysin stains 64%, and chromogranin A stains 29%. NSE stains 80% of bladder SmCC, but the specificity of NSE is very low.

Answer 17

The hallmark of Lynch syndrome is a genetic mutation in one of the family of DNA mismatch repair (MMR) protein genes (MLH1, MLH3, MSH2, MSH6, PMS2). These proteins function to repair errors in replication of DNA at short repetitive sequences (microsatellites). Lynch syndrome is associated with a high risk of colon and endometrial cancers, as well as increased risk of urothelial, small bowel, hepatobiliary, and pancreatic cancer. Further, 10-15% of sporadic colon, endometrial, and gastric tumors may harbor a somatic, non-germline MMR mutation or loss of expression.

Answer 18

Most labs have an MMR-IHC panel consisting of antibodies to four MMR proteins: MLH1, MSH2, MSH6, and PMS2. For efficiency and cost savings, some advocate primary screening with only MSH6 and PMS2. Intact expression of MSH6 and PMS2 generally translates to intact expression of MLH1 and MSH2; aberrant expression of MSH6/PMS2 then requires further IHC characterization. This strategy is based on the endogenous pairing of mismatch repair proteins, and an understanding of pairing is also necessary to interpret staining results. MLH1 and PMS2 form a heterodimer; if MLH1 is lost, PMS2 is also destabilized and expression is undetectable. However, since PMS2 has other binding partners, mutation or loss of PMS2 does not affect expression of MLH1. The MSH2/MSH6 heterodimer functions similarly; an MSH2 defect leads to loss of both MSH2 and MSH6, while an MSH6 mutation shows loss of MSH6 expression and intact MSH2 expression.

Answer 19

For efficiency and cost savings, some advocate primary screening with only MSH6 and PMS2. Intact expression of MSH6 and PMS2 generally translates to intact expression of MLH1 and MSH2; aberrant expression of MSH6/PMS2 then requires further IHC characterization. This strategy is based on the endogenous pairing of mismatch repair proteins, and an understanding of pairing is also necessary to interpret staining results. MLH1 and PMS2 form a heterodimer; if MLH1 is lost, PMS2 is also destabilized and expression is undetectable. However, since PMS2 has other binding partners, mutation or loss of PMS2 does not affect expression of MLH1. The MSH2/MSH6 heterodimer functions similarly; an MSH2 defect leads to loss of both MSH2 and MSH6, while an MSH6 mutation shows loss of MSH6 expression and intact MSH2 expression.

Answer 20

Since MMR proteins function in DNA repair, nuclear staining of replicating cells is expected normally. Epithelial cells at the base of normal colonic crypts are convenient internal controls, as are lymphocytes; in the uterus, endometrial stroma and myometrium may serve as internal control. MMR-IHC assays are particularly susceptible to under-fixation, especially MLH1 and PMS2. If internal controls are negative, repeat staining on another tissue block should be attempted; submission of additional tissue sections after longer fixation might also be helpful. MMR proteins may show patchy expression, especially MSH6 in post-chemotherapy specimens. Thus, even a low percentage of cells with nuclear staining should be scored as intact protein expression. In the case of MMR-IHC, positive staining is a normal result, while negative (lack of staining) is abnormal and suggests the need for further testing or genetic counseling. Other considerations in interpretation of IHC results include the fact that loss of expression of MLH1 may be due to a germline mutation in the MLH1 gene (Lynch syndrome), but is perhaps more commonly due to hypermethylation of the MLH1 promoter in older individuals. BRAF point mutations (V600E) are closely associated with this hypermethylation, and many testing algorithms advocate BRAF mutational analysis before embarking on genetic testing in patients whose colon cancers show loss of MLH1 expression.

Answer 21

CD56 and synaptophysin.

Answer 22

Human intestinal spirochetosis is defined histologically by the presence of spirochetal microorganisms attached to the apical cell membrane of colorectal epithelium. Human intestinal spirochetes include Brachyspira aalborgi and Brachyspira pilosicoli. Incidence is common in poorly developed areas, but low where living standards are high. Homosexuals and HIV+ individuals are at high risk. Most patients are asymptomatic, but children, homosexual and HIV+ men are more likely to be symptomatic regardless of invasion. The bacteria can be highlighted using silver stains, PAS, Giemsa, Alcian-blue (pH 2.5) and by immunohistochemistry. Intestinal spirochetosis often coexists with other enteric pathogens, including Entamoeba histolytica, Enterobius vermicularis, Helicobacter pylori, Shigella flexneri and Neisseria gonorrhoeae.

Answer 23

Positive: CAM 5.2, AE1, S100, p63 (secretory epithelium), CK8/18, EGFR. PAS+ diastase resistant secretions. Variable SMA, vimentin, type IV collagen and laminin (around glands). Negative: ER, PR, HER2. Actin, calponin, p63 (myoepithelial markers). EMA, GCDFP-15. p53, low Ki-67.

Answer 24

Microglandular adenosis: Infiltrative, ill-defined lesion. Glands are small, uniform, rounded, and open with dense eosinophilic secretions in lumens. Glands lined by single layer of cuboidal/flat cells with vacuolated/granular cytoplasm and bland nuclei; no snouting or nucleoli. EMA-, S100+. Tubular carcinoma: Stellate growth pattern, desmoplastic stroma. Glands vary in size and shape with angulated "tear-drop" appearance. Glands lined by cells with prominent apical snounts and without a surrounding basement membrane. EMA+, S100-.

Answer 25

Pulmonary carcinoids are positive for TTF-1 (only sometimes though) and negative for the others. Gastric and duodenal carcinoids are mostly positive for PDX-1 and negative for the others. Ileal carcinoids are positive for CDX-2 and negative for the others. Appendiceal carcinoids are positive for CDX-2 and negative for the others. Rectal carcinoids are negative for TTF-1 and CDX-2 and and almost all are negative for PDX-1.

Answer 26

PAS stain shows intracytoplasmic glycogen and PAS positive diastase resistant rhomboid crystals, a characteristic feature of ASPS. Nuclear expression of TFE3 is usually present. Muscle markers are expressed in less than half of cases. Cytokeratin, EMA, GFAP, and synaptophysin are negative. S100 is occasionally positive.

Answer 27

MH is an uncommon tumor that occurs almost exclusively in children; most cases are diagnosed in the first two years of life. It is the third most common liver tumor in this age group, following hepatoblastoma and infantile hemangioma. In most cases, serum AFP is normal or mildly elevated. MH may be solid or cystic, the latter being formed as a result of degeneration of the loose mesenchymal tissue. Extramedullary hematopoiesis is a frequent finding. The stroma tends to be more fibrotic in the rare adult cases. In some cases the mesenchymal component may dominate, with sparse ductal elements. The ductal elements express CK7 and lack CK20. The stromal cells are positive for SMA and vimentin.

Answer 28

The diffuse cytoplasmic positivity of chromophobe renal cell carcinoma with Hale's colloidal iron stain is due to staining of acid mucopolysaccharides.

Answer 29

Morphologically, they consist of sheets of medium-sized transformed lymphocytes with minimal pleomorphism, multiple nucleoli, and numerous admixed tingible-body macrophages. Immunophenotypically, they are CD20-positive B-cells that co-express CD10, BCL6, and CD43. They are typically negative for BCL2. Ki-67 is nearly 100%. There are very few admixed T-cells. On cytogenetic studies, >90% of cases show a translocation involving the MYC gene on chromosome 8. Most cases have the MYC gene juxtaposed with the IGH gene on chromosome 14, while a minority involves the kappa (chromosome 2) and lambda (chromosome 22) light chain genes.

Answer 30

ESS is CD10 positive, but other mesenchymal tumors such as smooth muscle tumors (highly cellular leiomyoma, leiomyosarcoma), adenosarcoma, and MMMT can be CD10 positive. Also, CD10 expression can be reduced in endometrial stromal sarcomas with variant histologic features (fibrosis, myxoid change, etc.). Therefore, CD10 is best used with a panel of other stains. Most of the tumors also express vimentin, ER, PR, WT1 (nuclear), bcl-2, and SMA; some express keratin and KIT. There can be scattered staining for desmin in some cases (in areas besides those of smooth muscle differentiation); so, like CD10, it should be used in a panel. Caldesmon is another smooth muscle marker expected to be negative in most ESS and is often included in diagnostic panels. Areas of sex cord differentiation may express inhibin, calretinin, melan-A, CD56, and CD99. EMA, DOG1, and CD34 should be negative in ESTs.

Answer 31

Cytokeratin. Paragangliomas generally do not stain with cytokeratins.

Answer 32

PAX2 and PAX8 belong to the pair box gene family consisting of 9 members, PAX1 through PAX9, each of which encodes a transcription factor. These transcription factors are expressed in an orderly manner during fetal development. They play a critical role in the formation of tissues and organs during embryonic development and are also crucial for maintaining the normal function of certain cells after birth. Although these 9 transcription factors control the development of a wide range of organs, the roles of PAX2 and PAX8 in ontogenesis are distinctively similar. Both of them are known to control the development of the central nervous system, eye, kidney, thyroid gland, organs deriving from the mesonephric (wolffian) duct, and those related to the müllerian duct. Transcription factors are identified in the nuclei of the cell types that are under their developmental control during organogenesis, but they often disappear in mature tissue. These transcription factors, however, may reexpress in an organ-specific fashion during neoplastic transformation. For example, both PAX2 and PAX8 are abundantly expressed by renal blastemal cells during nephrogenesis, then are noted in only a few renal parenchymal cells in mature kidney, but are identified again in RCC. Tissue expression of transcription factor therefore has been used as a specific marker for tumor diagnosis.

Answer 33

Adenosine triphosphate stains are used for distinguishing type-1 (slow, oxidative) and type-2 (fast, glycolytic) fibers. These are stains for enzyme activity, which require frozen sections, and can be technically difficult to perform. With the stain for myosin ATPase at pH ~10.5, type 2 myofibers are stained brown, and type 1 fibers are stained pink with an eosin counterstain to make them visible. The same stain, performed at a pH of ~4.3, would demonstrate staining of the type 1 myofibers, such that the section would show exactly the reverse pattern. Staining of normal muscle shows a random, almost checkerboard distribution of the 2 types of myofibers. However, IHC stains for slow myosin found in type-1 fibers and fast myosin found in type-2 fibers is available. Also, the IHC stains are permanent, but the myosin ATPase stain fades after a few months.

Answer 34

Histologically, the tumor is well circumscribed and may have a thin capsule. The cells can range from clear cytoplasm with minimal nuclear pleomorphism to very bubbly cytoplasm with moderate or even marked nuclear atypia. Despite areas of nuclear pleomorphism, mitoses are seldom found. The tumor is embedded in a rich anastomosing network of capillaries. Extramedullary hematopoiesis and mast cells can be part of the tumor, and, in some instances, patients may have increased erythropoietin that normalizes after the tumor is resected. Immunohistochemically, the tumor cells, also called stromal cells, have variable reactivity for NSE, S100, and CD56. Vimentin and VEGF are usually diffusely positive. Staining with GFAP is generally negative, but can be seen in some cells.

Answer 35

While this tumor has the historical name of hemangioma, electron microscopy and immunohistochemistry have shown an epithelial origin for this tumor. It is most frequently a solitary lung nodule, more common in women. Both radiographically and grossly these are well-circumscribed tumors. While they can be multiple and can involve lymph nodes, sclerosing hemangioma/pneumocytoma is a benign neoplasm clinically. There are 4 common patterns seen in these tumors: telangiectatic, epithelial/papillary, solid, and sclerotic. The immunohistochemistry profile of this tumor is distinctive, as the combination of cytokeratin and thyroid transcription factor 1 is generally diagnostic. While cytokeratin shows reactivity in the papillary proliferations, the bland solid areas are negative for this marker. In contrast, thyroid transcription factor 1 shows positivity in both the epithelial/papillary pattern and in the solid pattern. While foci can be positive for neuroendocrine markers (which at one point led to the speculation of a neuroendocrine tumor), these are not diffusely positive as in a carcinoid tumor. In addition, solid-growing areas of a carcinoid tumor are generally strongly cytokeratin positive.

Answer 36

Sclerosing hemangioma/pneumocytoma of the lung is IHC positive for cytokeratin and TTF-1, the combination of which is generally diagnostic.

Answer 37

While most commonly a tumor of pleura, intraparenchymal solitary fibrous tumor of lung can also occur. Aside from the location, solitary fibrous tumor of the lung is histologically identical to that of the pleura, with the exception that intrapulmonary solitary fibrous tumor has ingrowth of epithelial cells along clefts in the tumor. This can impart a leaflike growth pattern, which should not cause confusion with other neoplasms. The bland spindle cell population of a solitary fibrous tumor, alternating with areas of hyalinized collagen, is fairly distinctive; the addition of strong CD34 positivity is confirmatory.

Answer 38

While these are commonly encountered lesions, as incidental findings in lung tissue resections for other reasons, they are not generally the target lesion of a nodule or mass resection. There are rare cases in which these proliferations exceed 5 mm and are resected for concern of malignancy. They typically expand alveolar walls, imparting a stellate appearance to the lesions; the cellular expansion consists of bland cells with indistinct borders in nested and whorled patterns. They are typically positive for epithelial membrane antigen by immunohistochemistry. Despite their name and morphologic similarity, the even rarer true meningioma of the lung appears to harbor different molecular alterations from those of minute meningothelial nodules, raising the question as to whether they actually have related pathogenesis.

Answer 39

Keratin stains are very helpful in diagnosing desmoplastic mesotheliomas because they typically show spindled cells running downward (ie, away from the pleural surface) into fat. Care should be taken to ensure that what appears to be fat really is fat. Old paucicellular organizing pleuritis may show deep, fatlike spaces running parallel to the pleural surface, with keratin-positive cells between the ‘‘fat’’ cells. This "fake fat phenomenon" is really a biopsy/tissue processing artifact and the spaces are not fat but rather, traction artifacts in a fibrotic stroma. These traction/cutting artifacts may contain pale-staining ground substance. By contrast, true DMMs are both more cellular and have downward growth of spindle cells between fat cells rather than growth parallel to the pleural surface. S100 stains can be helpful because true fat is S100 positive and artifactual spaces are not.

Answer 40

Since complete hydatidiform moles are paternally derived, paternally imprinted genes that are normally expressed exclusively from maternally derived chromosomes should be absent. Studies have shown that p57KIP2, a paternally imprinted, maternally expressed gene, is useful in confirming the diagnosis of a complete mole, as the villous mesenchymal cells and villous cytotrophoblast of CHM are negative for this marker. PHM are p57KIP2 positive.

Answer 41

Hydropic abortus differs from CHM as (1) it typically is not associated with a markedly elevated ß-HCG level, (2) the volume of tissue removed is typically much less than that with CHM, (3) the villi appear swollen but lack true cistern formation, (4) the villi typically have a degenerative appearance in keeping with early embryonic demise, (5) the trophoblastic proliferation has a polar distribution with the formation of trophoblastic columns at one end of the villous and (6) are p57KIP2 positive.

Answer 42

In 1998, the US FDA classified IHC antibodies as analyte-specific reagents. Within this defined group, most antibodies are deemed Class I medical devices, exempting them from premarket FDA notification, which entails providing evidence of safety and efficacy. A few IHC markers, including ER and PR, are Class II medical devices, meaning they have associated guidance documents. The rationale behind Class I categorization is that IHC results are just one part of the final diagnostic interpretation by the pathologist. The flexibility provided by such a designation can be credited with rapid development of new antibodies, but lends itself to divergent practices and inconsistent results among labs. CLSI guidelines require that individual labs validate each new antibody; however, the details are left to the laboratory director. Predictive markers, such as HER2/neu, whose results bear prognostic and treatment implications, have been the first target of standardization. In 12/2006, ASCO and CAP introduced guidelines for HER2/neu testing, which were published in 1/2007. Additional measures toward enhanced quality include guidelines for validation of hormone receptor assays (2010), and in 6/2009, the CAP LAP added new checklist items that probe documentation of new antibody validation and verification of new lots of antibody.

Answer 43

Kaposi sarcoma lesional cells stain positively with the endothelial markers factor VIII–related antigen, CD31 (PECAM-1), and CD34. CD34 tends to show stronger expression than CD31 in advanced-stage lesions of KS. KS spindle cells also express several lymphatic specific markers such as D2-40 (which binds to the podoplanin antigen), LYVE-1 (a homologue of the CD44 glycoprotein receptor for hyaluronan), VEGFR-3 (the receptor for vascular endothelial growth factor C), and Prox-1. Bcl-2 also shows positivity in KS, related to the tumor's mechanisms of resisting apoptosis. The identification and localization of HHV8 within KS lesional cells by using LNA-1 (also called LANA-1) is the most diagnostically helpful immunostaining technique available to differentiate KS from its mimics. LNA-1 immunoreactivity in KS cells appears as stippled nuclear staining. However, HHV8 is not entirely limited to KS and has been detected in some angiosarcomas, hemangiomas, and dermatofibromas. LNA-1 IHC is favored over PCR detection of HHV8 in the evaluation of problematic vascular proliferations because contaminating mononuclear inflammatory cells may also harbor this herpesvirus, especially in HIV-positive patients.

Answer 44

Spermatocytic seminoma also has a distinctive histology of densely packed polymorphous cells which are composed of three distinct types: small (lymphocyte like), medium (15 - 20 µm) and large (number 50-100 µm). In contrast to classic seminoma, it is not associated with IGCNU. Additionally, immunohistochemical stains for PLAP and OCT3/4 are negative in spermatocytic seminoma whereas classic seminoma is positive.

Answer 45

Reticulin staining demonstrates fibers around groups and nodules of granulosa cells, and fibers that surround individual theca cells. JGCT is characteristically positive for inhibin and/or calretinin. Vimentin, keratin, and CD56 are positive in most cases, and WT-1 (nuclear) and S-100 are also frequently expressed. In contrast to other sex cord-stromal tumors, focal staining for EMA (<25% of tumor cells in most cases) can be seen in 25-50% of JGCTs. Most cases are positive for SMA, but desmin is negative.

Answer 46

TLE1 is one of four transducin-like enhancer of split (TLE) genes that encode human transcriptional repressors. It is an important protein in the Wnt/Beta-catenin pathway, a signaling pathway that is strongly associated with SS. Strong nuclear TLE1 expression is a robust IHC biomarker for SS, particularly in those cases that do not exhibit biphasic histology, and helps distinguish this tumor from other spindle cell tumors. In an appropriate clinical background and morphology, strong nuclear TLE1 expression in a CD34-negative spindle cell tumor containing scattered CK-positive cells can be regarded as diagnostic of SS.

Answer 47

Brenner tumors are generally positive for keratins, EMA, CEA, CK7, and glycogen. Evidence of urothelial differentiation in Brenner tumors is seen with reactivity for uroplakin III, thrombomodulin, and CK20. Brenner tumors are generally negative for p16 and p53. In contrast, TCC of the ovary rarely expresses the aforementioned urothelial markers. Reactivity for ER, WT-1, CA125, p16, and p53 has been observed in TCC of the ovary.

Answer 48

IHC stains for S100, CD57, myelin basic protein, and p53 are usually positive. Staining for S100 should be focally positive, but if strong, diffuse staining is present, a diagnosis of cellular schwannoma should be considered. MPNSTs are commonly negative for EMA, CK7, and CK19, which can differentiate this tumor from synovial sarcoma.

Answer 49

Clear cell sarcoma of soft tissue is a rare tumor that affects the extremities in young adults and shows melanocytic differentiation. This tumor is usually associated with tendons or aponeuroses and presents as a slow growing mass. Microscopically, the tumor grows in a uniform, nested to fascicular pattern with thin fibrous septa. Tumor cells are polygonal to spindle-shaped with abundant clear or eosinophilic cytoplasm and prominent nucleoli. Multinucleated giant cells are present in half of cases, and intracellular melanin can occasionally be seen. Clear cell sarcoma is positive for S100 protein, HMB45, and other melanocytic markers and shows a reciprocal translocation, t(12;22)(q13;q12), that results in EWS/ATF1 gene fusion.

Answer 50

Basically, podoplanin is the protein, and D2-40 is the antibody against that protein. Podoplanin is a mucin-type transmembrane glycoprotein that is expressed in lymphatic endothelial cells (and several other cell types). The mouse monoclonal antibody D2-40 was originally raised against an oncofetal antigen, M2A antigen, which is an O-linked sialoglycoprotein with a simple mucin-type carbohydrate epitope associated with germ cell neoplasms, but then this antibody clone was found to be reactive with other antigens/cell types as well. D2-40: = anti-podoplanin.

Answer 51

Antigen KI-67, also known as Ki-67 or MKI67 is a protein that in humans is encoded by the MKI67 gene. It is a nuclear protein that is associated with and may be necessary for cellular proliferation. Furthermore it is associated with ribosomal RNA transcription. Inactivation of antigen KI-67 leads to inhibition of ribosomal RNA synthesis. The Ki-67 protein (also known as MKI67) is a cellular marker for proliferation. It is strictly associated with cell proliferation. During interphase, the Ki-67 antigen can be exclusively detected within the cell nucleus, whereas in mitosis most of the protein is relocated to the surface of the chromosomes. Ki-67 protein is present during all active phases of the cell cycle (G1, S, G2, and mitosis), but is absent from resting cells (G0). Ki-67 is an excellent marker to determine the growth fraction of a given cell population. The fraction of Ki-67-positive tumor cells (the Ki-67 labeling index) is often correlated with the clinical course of cancer. Ki67 and MIB-1 monoclonal antibodies are directed against different epitopes of the same proliferation-related antigen. The Ki-67 protein was originally defined by the prototype monoclonal antibody Ki-67; The name is derived from the city of origin (Kiel, Germany) and the number of the original clone in the 96-well plate.Whereas Ki67 works only on frozen sections, MIB1 may be used also on fixed sections. MIB-1 is used in clinical applications to determine the Ki-67 labeling index. One of its primary advantages over the original Ki-67 antibody (and the reason why it has essentially supplanted the original antibody for clinical use) is that it can be used on formalin-fixed paraffin-embedded sections, after heat-mediated antigen retrieval.

Answer 52

SPN stains positive for alpha-1 antitrypsin, PR, vimentin, alpha-1 antichymotrypsin, CD10, CD56, NSE, beta-catenin and cyclin D1. Alpha-1 antitrypsin will generally also stain the intracytoplasmic hyaline globules that are also typically PAS-positive. Vimentin and NSE stain in a diffuse manner. PR staining is present in both male and female patients. Nuclear staining of beta-catenin is seen due to mutations in the beta-catenin gene which leads to unusual nuclear accumulation of beta-catenin, and since beta-catenin mutations lead to cyclin D1 upregulation, cyclin D1 is usually positive in SPN. SPNs stain variably for cytokeratins and synaptophysin. Only in rare instances are positive staining results seen for S100, pancreatic enzymes (trypsin, amylase, chymotrypsin, etc.), or pancreatic hormones (insulin, glucagon, and somatostatin). Most report chromogranin to be negative in SPN. SPNs characteristically lose E-cadherin expression. CD99 has a characteristic paranuclear dotlike pattern.

Answer 53

Cytologically, PanNET and SPN are both composed of fairly uniform round cells with uniform nuclei, but PanNET cells tend to have the speckled chromatin pattern typical of neuroendocrine neoplsms. While pseudopapillae may be present in PanNETs, their presence, along wiht foamy cells and hyaline globules, should favor the diagnosis of SPN. In cases where morphology is insufficient in differentiating the two, IHC should be performed. PanNET stains strongly for chromogranin and synaptophysin, and will generally stain for the expressed pancreatic hormone. SPN has variable staining for synaptophysin, it is typically much weaker than in PanNET, and does not stain for chromogranin. In addition, loss of E-cadherin is present in nearly all cases of SPN, but is variable in PanNET. CD56 and NSE are positive in both and provide little diagnostic utility between the two. Lack of PR staining is another useful diagnostic finding in PanNET. CD99 is positive in most PanNETs, but it has a membranous staining pattern that allows for easy differentiation from the staining pattern seen in SPN, which is a paranuclear dotlike pattern.

Answer 54

For light microscopy, an adequate specimen for diagnostic interpretation usually consists of three or more pieces of endomyocardium, each measuring at least 1-2 mm^3. Specimens for light microscopy evaluation should be placed in room temperature 10% buffered formalin. EM, IF, and nucleic acid studies can be accomplished with a single piece of myocardium for each study. The one exception is to increase the number of pieces for EM evaluation of anthracycline toxicity. Tissue for EM should be placed in glutaraldehyde fixative; tissue for IF should be frozen in Optimal Cutting Temperature compound or placed in Zeus solution, and tissue for viral nucleic acid studies should be frozen or placed in RNAlater RNA stabilizing solution. Specimens taken for EM should be processed to generate thick sections at which time the pathologist can determine if EM will add additional information to the case. If tissue was not originally submitted for EM processing and EM is desired, formalin-fixed tissue can be processed for EM, or paraffin-embedded tissue can be reprocessed for EM. Tissue taken for IF can be held and used when appropriate. IF can be useful for subtyping amyloid deposits and in the determination of cardiac nonamyloidotic Ig deposition disease. When viral myocarditis is suspected, tissue may be frozen or placed in RNAlater and then sent to a laboratory that has expertise in viral genome detection by assessment of nucleic acids.

Answer 55

A general consensus is that multiple sections (three or more) should be stained with H&E at different levels through the biopsy. For diseases that have a patchy distribution (sarcoidosis, myocarditis, etc.), even further sectioning can be performed if the entity is not seen on the initial slides. Intervening sections between H&E stains should be used for HC or IHC staining. A typical panel includes a collagen stain (Masson trichrome, Azan-Mallory, or Sirius red) for fibrosis, an elastic stain (Movat pentachrome, Verhoeff-Van Gieson) for endocardial fibroelastosis, a lymphocyte marker (CD3, CD8) for myocarditis, a macrophage marker (CD68) for myocarditis/myocyte injury, a glycogen stain (PAS) for glycogen storage disease, an amyloid stain (Congo red, thioflavin T, methyl violet, modified sulfated Alcian blue) for amyloid deposition, and an iron stain (Prussian blue) for hemochromatosis.

Answer 56

Grafts and stents should be examined for integrity of the wall and stenosis or thrombosis of lumen. The soft tissue around the graft may be included in the specimen and should be sampled. In infected grafts or stents, cultures are ideally obtained by the clinical team preoperatively or intraoperatively from blood, wound, sinus tract or perigraft fluid. Explanted stent grafts are examined grossly for evidence of structural graft failure such as fabric tears, fractures, kinks, or collapse. Synthetic vascular grafts can be sectioned easily with a surgical blade and submitted for microscopic evaluation along with its luminal contents and soft tissue.

Answer 57

Pattern #1: MLH1+, PMS2+, MSH2+, MSH6+; MSI phenotype is MSS or MSI-L; clinical interpretation is most likely sporadic CRC (Lynch syndrome very unlikely). Pattern #2: MLH1-, PMS2-, MSH2+, MSH6+; MSI phenotype is MSI-H; clinical interpretation is LS or sporadic CRC; etiology is germline hMLH1 mutation or hMLH1 promoter hypermethylation. Pattern #3: MLH1+, PMS2+, MSH2-, MSH6-; MSI phenotype is MSI-H; clinical interpretation is LS; etiology is germline hMSH2 mutation. Pattern #4: MLH1+, PMS2+, MSH2+, MSH6-; MSI phenotype is MSI-H; clinical interpretation is LS; etiology is germline hMSH6 mutation. Pattern #5: MLH1+, PMS2-, MSH2+, MSH6+; MSI phenotype is MSI-H; clinical interpretation is LS; etiology is germline PMS2 mutation.

Answer 58

FISH studies for cyclin D1 are very important in making a definitive diagnosis of MCL. Translocation t(11;14)(q13;q32) is the chromosomal rearrangement juxtaposing the cyclin D1 gene locus (CCND1) on chromosome 11q13 with the immunoglobulin heavy chain locus (IGH) located on chromosome 14q32, placing CCND1 under control of IGH enhancer sequences, and leading to over-expression of cyclin D1 protein. In addition to cyclin D1 immunoreactivity, MCL tumor cells are positive for pan-B-cell markers, CD19 and CD20. Surface immunoglobulin and IgM are also positive, with or without associated IgD positivity. Tumor cells also show CD5 immunoreactivity, and are negative or only weakly positive for CD23, a marker helpful in distinguishing between chronic lymphocytic leukemia/small lymphocytic lymphoma, which is typically positive for CD23.

Answer 59

Cytogenetically, hibernomas are often associated with rearrangements of chromosomal bands 11q13-21; however, other benign lipomatous tumors may also display such abnormalities. By IHC, hibernomas are variably positive for S100 protein and spindle cell components are positive for CD34.

Answer 60

The LAST Project recognized p16 as a biomarker for E6/E7 oncogene activation in all HPV-related precancerous squamous lesions of the LAT. Briefly, p16 staining is recommended whenever there is: Differential diagnosis between precancer (HSIL) and precancer mimics. Disagreement in interpretation of precancer. High risk for missing precancer (high-risk cytology with negative/LSIL biopsy findings). H&E morphologic pattern of -IN2 (This recommendation has proved to reduce the equivocal and poorly reproducible -IN2 diagnostic category. Positive p16 staining supports classifying -IN2 as definitive HSIL). Staining for p16 is not recommended for biopsies that are negative or show unequivocal LSIL or HSIL (-IN3).

Answer 61

Positive p16 staining is defined as strong and diffuse (continuous nuclear or nuclear and cytoplasmic) staining of the basal cell layer that involves at least the lower third of the epithelial thickness with or without full-thickness extension. p16 should be used in conjunction with standard morphologic diagnosis and not as a replacement.

Answer 62

UEC is a relatively uncommon neoplasm thought to have a higher prevalence than had previously been thought, as many cases of UEC were either reported as endometrioid endometrial carcinoma FIGO grade 3, or as HG sarcomas or carcinosarcomas. UEC, compared to endometrioid adenocarcinoma FIGO grade 3 (the main differential diagnosis), carries a much worse prognosis. Involvement of and origin from the LUS is a frequent finding. Microscopically, it is defined as a tumor composed of medium or large-sized cells with complete absence of glandular differentiation and with absent or minimal (<10-20% of tumor cells.

Answer 63

Undifferentiated/dedifferentiated endometrial carcinoma: 55, 45%, diffuse patternless sheets, absent, vague, dyshesive cells, sharp demarcation, may be present, may be present, patchy/focal, patchy/focal, focal in 12% of cases. Endometrial adenocarcinoma FIGO grade 3: 68, 30%, solid and glandular, present (1-49% of tumor area), well demarcated, cohesive squamoidlike, intermingled components, absent, absent, diffuse, diffuse, diffuse in 60% of cases.

Answer 64

True glandular lumina are lined by ductal epithelium (EMA+, keratin+, CD117+) and eosinophilic “cylinders” with basement membrane material are lined by basal / myoepithelial-type cells (p63+, S100+, smooth muscle actin+, vimentin+). Secretions in the true lumina are PAS+ diastase resistant, and cribriform spaces are Alcian blue+. All salivary gland tumors of the breast, including adenoid cystic carcinoma, are characteristically negative for ER, PR, and HER2 (triple negative), and express basal cell markers CK5/6, P-cadherin and p63.

Answer 65

Bright CD20, bright sIg, CD38 expression, and ZAP-70 expression. ZAP-70 is the Z-chain-associated protein-70, a tyrosine kinase normally associated with the T-cell receptor (TCR) Z chain.

Answer 66

Enteric differentiation can occur in lung adenoCA and when this component exceeds 50%, the tumor is classified as pulmonary adenoCA with enteric differentiation. The enteric pattern shares morphologic and IHC features with CRC. In contrast to metastatic colorectal adenoCA, these tumors are histologically heterogeneous with some component that resembles primary lung adenoCA such as lepidic growth. The enteric pattern consists of glandular and/or papillary structures, sometimes with a cribriform pattern, lined by tumor cells that are mostly tall columnar with nuclear pseudostratification, luminal necrosis, and prominent nuclear debris. Poorly differentiated tumors may have a more solid pattern. These tumors show at least 1 IHC marker of enteric differentiation (CDX-2, CK20, or MUC2). Consistent positivity for CK7 and expression of TTF-1 in ~50% of cases help in the distinction from metastatic CRC. CK7 negative cases may occur. CDX-2 is reduced or absent in most poorly differentiated CRC and more than half show the high-frequency MSI phenotype. Although this type of tumor will rarely metastasize to lung, since IHC detection of MMR proteins (MLH1, MSH2, MSH6, and PMS2) gives a predictive value that is virtually equivalent to MSI testing, this may be worth testing in selected cases as MSI in primary lung adenoCA is extremely rare. Primary lung adenoCA that histologically resemble CRC but lack IHC markers of enteric differentiation are probably better regarded as lung adenoCA with enteric morphology rather than lung adenoCA with enteric differentiation.

Answer 67

In RFH, the germinal centers usually remain separate and vary in size (but they may coalesce in some cases). The germinal centers contain numerous mitoses and tingible-body macrophages. Staining with bcl-2 is weak or absent within the germinal center (but strong in the surrounding mantle), while PCNA (Ki-67, proliferating cell nuclear antigen) is strongly expressed. In follicular lymphoma, follicles are often "naked" (mantles are obliterated) and confluent. Mitoses and tingible-body macrophages are rare. Staining with bcl-2 is strong in the follicle, and PCNA is weak.

Answer 68

The role of IHC is in the distinction of benign hepatocellular nodules from reactive hepatocytes; WD-HCC from benign hepatocellular nodules; poorly differentiated HCC from cholangiocarcinoma and metastases; and determination of histogenesis of malignant tumor; and of primary site of origin of malignant tumor. A panel of antibodies has more discriminant value. AFP expression usually indicates malignancy in a hepatocellular nodule and hepatocytic histogenesis of a malignancy. pCEA and CD10 stain bile canaliculi in better-differentiated HCC. HepPar1 is generally accepted as a hepatocytic marker. However, not all HCC stain uniformly and not all HepPar1-positive tumors are of hepatocytic origin or arise in the liver. Mature hepatocytes and hepatocellular nodules stain with CAM 5.2, CK 8, and 18 but not with CK 7, 19, 20, or AE1/AE3. Biliary epithelium expresses CK 7 and 19. CD 34 highlights sinusoidal capillarization. AFP, pCEA/CD10, and CD34 are useful for ascertainment of malignancy in hepatocellular nodules; HepPar1 and cytokeratins to be included if histogenesis is the issue. IHC results should be interpreted in the larger context of the case.

Answer 69

Steroid cell tumor, NOS can occur over a wide age range; however most patients tend to be younger than those with the other types of ovarian steroid cell tumors with an average age of 43 years at presentation. Approximately 50% of patients present with virilization and hirsutism. A minority will present with estrogenic manifestations or occasionally Cushing syndrome due to cortisol production by tumor cells. The vast majority of tumors are unilateral and they are typically well circumscribed, lobulated or multinodular solid yellow to orange to brown tumors that may occasionally exhibit hemorrhage and/or necrosis. These tumors have an average size of 8.4 cm. Histologically, most show a diffuse pattern of growth, but they may also have a clustered or corded growth pattern as evident in this case. There is typically little intervening stroma, but there is often a rich vascular network of thin compressed capillaries. The tumor cells have moderate amounts of granular eosinophilic or vacuolated cytoplasm with distinct cell borders and centrally placed round and regular nuclei with conspicuous nucleoli. Cytologic atypia is uncommon and mitotic activity is usually low (<2 per 10 high power fields). Occasionally, hemorrhage and necrosis can be present. Tumor cells are positive for inhibin and calretinin, but are usually negative for keratin.

Answer 70

INI1/BAF47 deletions are detected in ~70% of atypical teratoid/rhabdoid tumors; however, loss of the corresponding INI1 protein is even more common than the genetic alteration. Loss of INI1 nuclear immunoreactivity in tumor cells is used as a surrogate for genetic testing to demonstrate biallelic inactivation of the gene.

Answer 71

Isocitrate dehydrogenase (IDH1/IDH2) mutations have been detected in the majority of diffuse gliomas, with the notable exception of primary (de novo) GBM, and appear to play a fundamental and early role in oncogenesis. The most common mutation is in the IDH1 gene (R132H), and is recognized by monoclonal antibody IDH-1. Diagnostically, the IHC stain shows greatest promise for its potential to distinguish low-grade diffuse glioma from gliosis. Prognostically, the presence of this mutation is favorable, as such tumors appear to show greater response to therapy.

Answer 72

Microglial cells are of monocytic lineage and are consequently immunoreactive for LCA, CD68, and CD163. In response to various signals, these cells undergo activation, whereupon they change their morphology (appearing as irregular elongated "rod cells"), become motile, and intensify their communication with other cells via secreted factors such as cytokines and interleukins. They may also participate in limited phagocytosis.

Answer 73

Phosphotungstic acid hematoxylin (PTAH) stains cytopasmic mitochondria dark blue-black. Novelli stains cytoplasmic mitochondria blue-purple. Luxol fast blue shows metachromatically positive mitochondria in cytoplasm. Cresylecht violet V reaction shows metachromatically positive cytoplasmic granules.

Answer 74

Well circumscribed but variably encapsulated. Broad range of appearances due to multiple architectural patterns (solid, myxoid, reticular, nested, cord-like). Typically composed of spindled or plasmacytoid cells; may have dominant cell type or mixed morphology; plasmacytoid cells with hyperchromatic, round to oval nuclei and abundant, eccentric eosinophilic cytoplasm (characteristic but not pathognomonic, as also seen in pleomorphic adenoma of palate). Although not common, clear, polygonal (epithelioid), or stellate cells may be seen. Background with variable collagenization; may contain abundant acellular mucoid stroma. Lacks chondroid or myxochondroid matrix. Lacks infiltration, perineural invasion, profound pleomorphism, necrosis, increased mitotic figures. IHC: Reactive with pan-CK, CK7, CK14, p63, GFAP, and S100. Variable reactivity with actin-sm, actin-HHF-35, SMHC, and calponin (actins reactive in spindled cells but typically nonreactive in plasmacytoid cells). Mutations of p53 have been observed. DDx: pleomorphic adenoma, myoepithelial carcinoma, spindled soft tissue neoplasm, plasmacytoma.

Answer 75

Immunerable architectural patterns (solid, tubular, trabecular, cystic). Epithelial tissue shows variable morphology (spindle, clear, squamous, basaloid, plasmacytoid). Mesenchymal-like tissue (myxoid stroma, myxochondroid, hyaline stroma, rarely lipomatous, bone). Duct structures (lined by cuboidal or columnar epithelium). Rarely, crystals are present: collagenous crystalloids (eosinophilic needle shapes arranged radially), tyrosine-rich crystalloids (eosinophilic bunted shapes arranged tubularly), crystalloids resembling oxalate crystals. Occasionally squamous metaplasia is identified. Rare necrosis. Rarely sebaceous cells. IHC is sensitive but not specific: panel of CK, p63, GFAP, S100, and SMA recommended (all will be variably positive).

Answer 76

A benign salivary epithelial neoplsm composed of basaloid cells lacking chondromyxoid stroma. ~2-3% of all salivary gland neoplasia. Wide age range, peak in 6th to 7th decades. M:F = 1:2. ~75% in parotid gland. Micro: All subtypes are composed of basaloid cells (may display 2 cell morphologies). Squamous eddies, drop-like eosinophilic hyaline material, and small ductal structures possible. Multiple architectural subtypes (solid, trabecular, tubular, and membranous patterns). All patterns demonstrate stroma of variable amount and collagenous density. IHC: Keratin variably reactive in all epithelial cells (strongest in inner, larger basaloid cells). Actin-sm, p63, and calponin reactivity in peripheral, smaller basaloid cells. S100 may be variably reactive in both epithelial cell types. DDx: Basal cell adenocarcinoma. Canalicular adenoma. Adenoid cystic carcinoma.

Answer 77

Micro: Papillary and cystic lesion composed of epithelial and lymphoid components. Epithelial component lining the papillary projections composed of double layer of granular eosinophilic cells (referred to as oncocytic epithelia). Inner or luminal cells: Nonciliated, tall columnar cells with nuclei aligned toward luminal aspect. Outer or basal cells: Round, cuboidal, or polygonal cells with vesicular nuclei. Lymphoid component predominantly composed of mature lymphocytes containing lymphoid follicles with germinal centers. Epithelioid and lymphoid components are sharply demarcated from one another. Other imflammatory cells may be seen, including plasma cells, histiocytes, mast cells, and occasional multinucleated (Langhans-type) giant cells. Lumens of cysts may contain thick secretions, cholesterol crystals, cellular debris, or corpora amylacea-like laminated bodies. Squamous metaplasia and focal necrosis may be seen in association with secondary inflammation. Due to presence of oncocytic cells, WT is subject to degenerative alterations occuring spontaneously or following manipulation. Metaplastic or infarcted variant of WT accounts for <10% of all WT. IHC: All epithelial cells are panCK positive. Luminal (or inner) epithelial cells are CK7, CK8, CK18, and EMA positive. S100, p63, calponin, GFAP, and actin negative. Lymphoid cells reactive for CD20, CD3, CD56, CD4, and CD8. Cytogenetics: t(11;19) translocation and CRTC1/MAML2 fusion transcript identified. DDx: Cystadenoma. Other numerous slivary gland tumors with oncocytic cells.

Answer 78

AKA monomorphic adenoma. ~2% of all salivary gland tumors, ~4% of all benign tumors, and ~20% of all lip salivary gland tumors. Wide age range, mean 65 yrs. M:F = 1:2. Vast majority in upper lip. Micro: Encapsulated. Canalicular pattern with cords and ribbons showing connection points between opposing columnar cells within spaces (Beading: columnar cells abutting one another within tubules. This beading of columnar cells is characteristic). Tubules interconnect in lattice-like architecture. CUboidal to columnar cells. Basaloid cells with round to oval nuclei. Scant, slightly eosinophilic cytoplasm. No mitotic figures. Loose, fibrillar stroma; rich in hyaluronic acid and chondroitin sulphate. Calcifications may be seen (microliths). IHC: Various keratins are positive, as well as S100 and CD117. SMA, calponin, SMMHC, p63, GFAP negative. DDx: Basal cell adenoma. Adenoid cystic carcinoma.

Answer 79

Micro: Well circumscribed, well encapsulated, pushing yet noninfiltrative border. Epithelial element: Evenly dispersed solid epithelial nests with bland cytology and cysts of variable size (squamoid, columnar, or cuboidal lining; may contain secreted material). SLA: sebaceous cells in solid nests or within cyst walls. LA: lack of sebaceous component. Lymphoid component: Uniformly dense. Germinal centers may be focal to numerous. No infiltration/invasion of epithelial component. Foreign body reaction may be present due to cyst rupture. IHC: PanCK pos in epithelial component. p63 pos in basal layer of sebaceous nests. Lymphoid markers (CD3, CD20, Bcl-2, etc) confirm reactive, hyperplastic lymphoid population. DDx: Warthin tumor. Tumor-associated lymphoid proliferation. Metastatic carcinoma.

Answer 80

All histologic variants of hemangioma occur in salivary glands, but capillary (juvenile) hemangioma is most common. Hemangiomas account for 90% of parotid gland tumors in infants <1 yo are hemangioma. Capillary (juvenile) hemangiomas have M:F = 1:3, while cavernous hemangiomas tends to be seen more frequently in older males. Parotid gland involved in 90%, and up to 25% are bilateral. Pediatric tumors initially grow rapidly, but 75-95% spontaneously involute before 7 yo, and many earlier. Pharmacological therapy (corticosteroids and interferon) yields a response in up to 98% of cases. IHC: Endothelial cells pos for CD31, CD34, FVIIIRAg. Residual salivary ducts are keratin pos. GLUT1 pos in juvenile hemangiomas.

Answer 81

Cystic spaces: often filled with mucin, occ papillary projections present. Epidermoid cells: nests or scattered; polygonal cells. Intermediate cells: large polygonal epidermoid cells; small basal cells; often in nests or sheets. Mucous cells: intracytoplasmic mucin; large or ovoid; vacuolated or clear cytoplasm; in groups or individual cells. Clear cells: usually <10% of cells but can be a dominant finding; contain glycogen or mucin. Spilled mucus: incites inflammatory response. Tumor-associated lymphoid proliferation: lymphoid cells with occ germinal centers; may be confused with met disease to a lymph node. Necrosis, anaplasia, and mitoses variably present. PNI and ALI can be seen. Sarcomatoid transformation rarely seen. IHC: p63 has strong basal cell nuclear pos, and may highlight intermediate as well as epidermoid cells. CK5/6 highlights epidermoid-type cells but is often neg in transitional cells. Ki-67 high expression seen with increased proliferation, usually indicative of HG tumor. HER2 tends to be strongly reactive in HG tumors. Cytogenetics: t(11;19)(q21-22;p13) fuses mucoepidermoid carcinoma translocated 1 (MECT1) with Mastermind-like gene family (MAML2); is identified in LG to IG tumors only. Other abnormalities include variable losses of 2q, 5p, 12p, and 16p. Aneuploid tumors have a higher recurrence rate, higher cervical LN involvement, and decreased survival.

Answer 82

Micro: Infiltrative (PNI commonly seen; infiltrative edges into fat, skeletal muscle, soft tissue). Combinations of patterns usually present, although one predominates. Patterns: cribriform, tubular, and solid. Cytologic features: small to medium cells with eosinophilic to clear cytoplasm; nuclei are oval to sharply angulated with coarse, basophilic chromatin and occasional small nucleoli; mitotic figures are rare except for in the solid pattern. HC: Alcian blue and PAS highlight basement membrane material of pseudolumina. IHC: May have limited practical use, as tumors in DDx often react similarly. DDx: PLGA, PA, basal cell adenocarcinoma, basal cell adenoma, epithelial-myoepithelial carcinoma, CExPA, basaloid SCC, cylindroma, sialoblastoma, NEC. Cytogenetics: No particular gene profile identified. 30% have translocations involving 9p13-23 and 6q. ~50% have loss of chromosome 12q12. LOH at 6q23-25 is associated with poorer prognosis. Alteration of p53 is associated wtih tumor recurrence and progression to solid type.

Answer 83

Micro: Tumor extension into normal tissue is common, although "apparent" encapsulation is present. Although one pattern and cell type dominate, combination and spectrum is common. Patterns: solid/lobular > microcystic > papillary-cystic > follicular. Several cell types are present: serous acinar cells > intercalated duct type cells > vacuolated cells > nonspecific glandular cells > clear cells. Lymphoid infiltrate, sometimes prominent with germinal center formation, can be seen. Stromal fibrosis or desmoplasia is uncommon. HG transformation (dedifferentiation) into HG carcinoma (including small cell carcinoma) is rare and heralds poor prognosis. HC: PAS+, diastase-resistant zymogen granules (reaction can be patchy and limited). Neg or only focally pos granules with mucicarmine. IHC: Immunoprofile is nonspecific and unpredictable, so seldom of diagnostic value. Cytogenetics: No consistent or specific structural chromosomal alterations. DDx: normal salivary gland, papillary cystadenocarcinoma, mucoepidermoid carcinoma, metastatic thyroid carcinoma, clear cell tumors (epithelial-myoepithelial CA, clear cell adenoCA, clear cell oncocytoma, met RCC), PLGA.

Answer 84

Micro: Infiltrative growth, architectural diversity, and cytologic uniformity, set in characteristic matrix. Infiltrative growth: Unencapsulated, but usually well circumscribed. Encased, entombed, incarcerated, or completely surrounded minor salivary glands. Invades into soft tissues, especially fat. Bone invasion can be seen. Significant PNI. Patterns of growth: Striking variety of growth patterns. Low power gives "eye of the storm," "streaming" or "whorled" appearance. Characteristic concentric layering of cells around central nidus, creating targetoid tableau. Periphery often shows linear, single-file cell infiltration. Arranged in lobules, theques, glandular profiles, tubules, trabeculae, and cribriform nests. Papillae, if identified, are focal and not dominant pattern. Cellular features: Uniformly bland round to polygonal or fusiform tumor cells. Small to medium, with indistinct cellular borders. Ample pale to eosinophilic cytoplasm. Round to oval nuclei with open, vesicular nuclear chromatin. Inconspicuous to small nucleoli. Matrix material: Slate gray-blue stroma usually only focal. Hyalinized, slightly eosinophilic stroma separates cells. Inconspicuous mitoses. Tyrosine-like crystals are identified in <5%. Rare metaplastic changes: squamous, sebaceous, mucous, clear, oncocytic. IHC: Variable expression of epithelial and myoepithelial markers. Cytogenetics: Chromosome 12 abnormalities are most common: p or q arms (12q22 and 12p12.3).

Answer 85

Micro: Variably sized, rounded, solid or cystic nodules of tumor cells that resemble intraductal or infiltrating ductal carcinoma of the breast. Small nodules are filled with neoplastic cells. Larger cystic nodules with irregular shape. Comedonecrosis is conspicuous. PNI and LVI frequent. Marked, dense, desmoplastic (hyalinized) fibrosis is conspicuous. Lymphoplasmacytic inflammator cell infiltrate is frequently present. Cells are arranged in cribriform, band-like solid, and papillary patterns. Small tumor nests infiltrate between larger nodules. Epithelial cells have moderate to marked pleomorphism, are cuboidal to polygonal, with ample eosinophilic granular, oncocytic cytoplasm. Nuclei are round, centrally located, with large, prominent nucleoli and hyperchromatic chromatin. Mitotic figures, including atypical forms, are usually easily identified. Uncommonly, psammoma bodies and areas of squamous differentiation seen. Variants: sarcomatoid, micropapillary, mucin-rich, osteoclast-type giant cell, low-grade SDC (controversial entity). HC: Nonreactive with mucicarmine and Alcian blue. IHC: Pos for epithelial markers, androgen receptor, HER-2/neu. Cytogenetics: Frequent LOH involving 9p21, 6q, 16q, 17p, and 17q regions.

Answer 86

According to the World Health Organization (WHO), thymic epithelial tumors with predominant neuroendocrine differentiation are classified as Neuroendocrine carcinomas (NEC) of the thymus. Thymic neuroendocrine carcinomas are classified as well-differentiated NEC (typical carcinoid and atypical carcinoid) and poorly differentiated NEC(large cell NEC and small cell NEC). The main differential diagnosis includes: Metastatic pulmonary NEC (TTF1+ may be helpful). Thymic carcinoma with focal neuroendocrine differentiation. Nerve sheath tumor (CK-, chromo-, synapto-). Paraganglioma (CK-).

Answer 87

ALK-positive DLBCL has a cytoplasmic granular staining pattern, while the majority of anaplastic large cell lymphomas have nuclear and cytoplasmic staining.

Answer 88

The terms validation and verification are often used interchangeably. Strictly speaking, however, they apply to different types of IHC assays. Verification is the process by which a laboratory determines that an assay performs according to the recommendations set forth by the manufacturer as documented in the product insert at the assay conditions determined during the optimization step. This process typically involves staining a number of cases that span the range of expected protein expression of the chosen protein, including a number of anticipated negative cases. The laboratory director should determine the number of cases that should be stained. Generally speaking, the number of cases to be tested during verification is larger if the results are to be used solely as a prognostic or predictive marker (for example, HER2). Also, if the number of result categories is higher than simply positive or negative, the number of verification cases should be high enough to test each of the result categories. Validation is a more rigorous process than verification and applies only to laboratory-developed tests (LDTs). Since the test performance characteristics of an LDT have not, by definition, been determined by a manufacturer, a greater number of cases must be stained to confirm that the LDT performs according to the specifications determined by the laboratory director. Both verification and validation require that the results of the assay be compared to a known standard. These standards include cases stained in the same laboratory using a previously validated/verified assay, cases stained in another laboratory with a validated/verified assay, comparison with another technique, or comparison of results with findings reported in the peer-reviewed literature.

Answer 89

Optimization is the process by which the laboratory director determines provisional assay conditions, which most often involves staining a single case or small number of cases at varying assay conditions. The conditions that may be altered include primary antibody dilution, duration of primary antibody incubation, type of antigen retrieval buffer, antigen retrieval time, and detection chemistry, with the goal of having the strongest positive reaction with appropriate subcellular localization and minimizing, or eliminating, any reaction in cells that do not contain the protein in question. Once the laboratory director is satisfied that the quality of staining is optimal, as assessed in this small number of cases, one can proceed to the validation or verification step.

Answer 90

Type I pneumocytes are large, flat, squamous alveolar lining cells; covering ~93% of alveolar surface area. Type I cells are incapable of division. They provide a thin air-blood interface for gas transfer. Type I pneumocytes stain with epithelial markers such as AE1/AE3, caveolin, and aquaporin. Type II, or granular, pneumocytes are cuboidal to columnar alveolar lining cells. Gas exchange takes place across the cytoplasm of type I cells. Type II cells are the progenitors for type I cells, synthesize and secrete surfactant (lamellar ultrastructural inclusions), and proliferate after injury to restore alveolar epithelial integrity. Type II cell hyperplasia (alveolar cell hyperplasia) represents a nonspecific marker of alveolar injury and repair. Type II pneumocytes stain with epithelial markers such as AE1/AE3, and surfactant protein C.

Answer 91

The low-grade myofibroblastic proliferations of the urinary bladder are rare lesions affecting males more often than they do females. The most-common signs and symptoms are hematuria and dysuria. Histopathologically, they are spindle cell proliferations in a loose myxoid stroma, even though compact proliferations or hypocellular fibrous patterns can be found. Typically, there are varying amounts of acute, chronic, or mixed inflammatory infiltrates. Necrosis is rare to absent. Muscularis propria infiltration is common, while perivesical soft tissue invasion is uncommon. IHC is nonspecific, except for ALK-1 positivity (20%–89%). FISH has demonstrated clonal genetic aberrations involving the ALK gene in 50% to 60% of cases. After surgery, only 6% of patients experience local recurrence, without metastases or deaths from the disease. Malignant transformation has been reported exceptionally. These myofibroblastic proliferations are probably part of a continuum with, at one end, benign pseudosarcomatous proliferations and, at the opposite end, more-aggressive lesions.

Answer 92

Primary effusion lymphoma cells typically display a “null” lymphocyte phenotype: CD45 is expressed, but common pan–B-cell (CD19, CD20, CD79a, surface immunoglobulins) and T-cell (CD3, CD4, CD8) markers are absent. Instead, however, markers of lymphocyte activation (CD30, CD38, CD71, EMA, HLA–DR) and plasma cell differentiation (CD138) are often present. Bcl-6 is usually absent. Definitive diagnosis hinges on detection of viral infection by HHV8 in the neoplastic cells. IHC to detect expression of latency-associated nuclear antigen, LANA-1, are currently the standard assay to demonstrate evidence of infection; typically, positive results are characterized by a nuclear dotlike pattern. Epstein-Barr virus infection can be demonstrated by ISH for EBV-encoded small RNA (EBER); IHC studies for EBV latent membrane protein 1 are negative. Viral interleukin 6 is expressed by a variable subset of lymphoma cells, and IHC studies for this protein may be helpful for confirmation.

Answer 93

GI schwannoma: commonly has a peripheral lymphoid cuff, frequent cell size variation, no skeinoid fibers, S100 positive in 100%, GFAP positive in 65-100%, CD117 negative. Bland spindled GIST: lacks peripheral lymphoid cuff, generally uniform cell size, may have skeinoid fibers, S100 positive in 5% (20% in small intestine), GFAP negative, CD117 positive in 74-95%.

Answer 94

Substances containing vicinal glycol groups or their amino or alkylamino derivatives are oxidized by periodic acid (an oxoacid of iodine, so is pronounced PURR-eye-OH-dik) to form dialdehydes, which combine with the Schiff reagent (detects aldehydes) to form an insoluble magenta compound.

Answer 95

Classic EATL: CD3+, CD5-, CD7+, 80% CD8-, >90% CD56-. Type II EATL: CD3+, CD5-, CD7+, 80% CD8+, >90% CD56+.

Answer 96

Villin is an actin binding protein present in cytoskeleton of intestinal microvilli; has critical role in maintaining brush border organization. It is relatively specific for GI epithelium with brush border microvilli or adenocarcinomas derived from them. Positive staining (normal): Digestive tract epithelium, proximal renal tubules, hepatic bile ducts. Positive staining (disease): Colonic adenocarcinoma, renal cell carcinoma, pulmonary adenocarcinomas. Negative staining: Renal distal tubules, bronchiolar epithelium, pulmonary alveolar cells, bronchial gland cells. Uses: Primary bladder adenocarcinoma (villin-, CDX2-) vs. colorectal carcinoma to bladder. Ovarian adenocarcinoma (villin-) vs. colorectal adenocarcinoma.

Answer 97

Also called BSAP, a B cell-lineage specific activator protein at 9q13. Member of paired box (PAX) family of transcription factors, which have a novel, highly conserved DNA-binding motif, known as the paired box; encodes BSAP expressed at early stages of B-cell differentiation, also in developing CNS and testis. Detected in B cells from pro-B cell stage to plasma cell stage where it is downregulated. Required for progression of B cell development beyond the early pro-B cell stage. Uses: Detection of pre-B cells (PAX5+, more sensitive and specific than CD20). Diagnosis of Reed-Sternberg cells in classic Hodgkin lymphoma (PAX5+) versus T / null cell anaplastic large cell lymphoma (PAX5-), although rarely positive in T cell lymphomas. Diagnosis of lymphoplasmacytic lymphoma / plasmacytoid differentiation in marginal zone lymphoma (PAX5+) versus plasmacytoma (PAX5-).

Answer 98

In lobular neoplasms, p120 yields a diffuse cytoplasmic immunostaining pattern. Conversely, ductal neoplasms retain the dominant membrane immunostaining pattern of p120 catenin. The presence of weak membranous positivity for p120 may be observed in a small subset of ductal carcinoma cases, which could lead to misinterpretation as a lobular phenotype. Complete lack of β-catenin membranous expression is associated with lobular histologic type, while expression of β-catenin is observed in virtually all cases of ductal carcinoma, both in situ and invasive.

Answer 99

Black: nuclei, elastic fibers. Yellow: collagen fibers, reticular fibers. Blue: ground substance, mucin. Red: fibrin. Bright red: muscle.

Answer 100

Uterine Tumors Resembling Ovarian Sex Cord Tumors. Rare neoplasm of unknown etiology occuring usually in middle-aged women. In line with its controversial origin, the current WHO classification placed UTROSCTs in the "miscellaneous" category of tumors of the uterine corpus. A multitude of architectural patterns are described, including plexiform cords, anastomosing trabeculae, watered silk, microfollicle, macrofollicle, tubules, retiform, solid cellular islands, and diffuse pattern. Mitotic figures are infrequent and necrosis is mostly absent. This tumor has a diverse IHC profile with expression of sex cord, epithelial, and smooth muscle markers. Immunoexpression of calretinin and at least for one of the other sex cord markers is required to establish a diagnosis. Most have benign behavior, but some recur, so should be considered a tumor of low malignant potential.

Answer 101

No. Aggressive angiomyxoma typically occurs in the genital and pelvic regions of women of reproductive age and rarely occurs in the inguinal region, along the spermatic cord and in the scrotum of men. This neoplasm typically has infiltrating borders and shows scattered spindled and stellate shaped cells with thin and thick-walled blood vessels in a myxoid background. The spindled cells are generally positive for actins and desmin and consistently express both estrogen and progesterone receptors, but are negative for S-100.

Answer 102

Alkaptonuria, an autosomal recessive disorder of amino acid metabolism. Increased homogentisic acid is secreted in urine and polymerized homogentisic acid deposits accumulate in connective tissue. The pigment is Fontana-Masson positive and Prussian blue negative.

Answer 103

Cytoplasmic retraction that is a formalin fixation artifact. The artifact is not seen in tissue placed in metal-containing fixatives such as B5, where the cells have ample pale-staining cytoplasm.

Answer 104

The villous cytotrophoblasts and stromal cells in complete mole are negative or have only focal nuclear staining, while there is diffuse positivity in partial mole and hydropic abortus. Syncytiotrophoblastic cells are also negative for p57. It should be noted, however, that intervillous intermediate trophoblasts and decidual cells in complete mole do stain for p57.

Answer 105

Beta-amyloid precursor protein is a neuronal transmembrane glycoprotein that is transported by fast anterograde axoplasmic flow. In an uninjured brain, the protein is diffusely distributed in the axons and is not detected by the stain. In traumatic axonal injury, tearing or stress causes damage to the neuronal cytoskeleton and interrupts axonal transport. With axonal injury, the protein accumulates focally and can be detected by the IHC stain. Ischemic injury or traumatic axonal injury may result in accumulation of the protein, so anatomic location of the staining is important for interpretation.

Answer 106

Beta-amyloid precursor protein needs a survival interval of at least 2 hours to detect neuronal injury. Histochemical stains such as silver stain need survival intervals of at least 12 hours to detect injured neurons.

Answer 107

Up to 10% of DLBCL are positive for CD5. In this case, make sure it is not CLL/SLL or mantle cell lymphoma that has transformed.

Answer 108

Vimentin positive. MUC4 positive. EMA focally positive. Negative: S100, GFAP, caldesmon, ALK-1, c-kit, nuclear beta-catenin.

Answer 109

IHC cannot distinguish HA (biparental diploidy) from PHM (diandric triploidy). Short tandem repeat genotyping, which determines the parental source of polymorphic alleles, is useful.

Answer 110

BZLF1, which represents the Z gene of the virus that is implicated in the switch from latency to lytic cycle of the virus causing its replication; all of the other markers including EBER-1 are considered latency genes and do not necessarily reflect replicating virus or active infection.

Answer 111

DF: CD34-, CD163+, FXIIIA+. DFSP: CD34+, CD163-, FXIIIA+/-.

Answer 112

Immunostaining for enzymes involved in catecholamine biosynthesis such as tyrosine hydroxylase can differentiate it from other endocrine tumors.

Answer 113

ATRTs are highly malignant (WHO grade IV) CNS neoplasms seen in very young children. INI1 is a ubiquitously expressed protein encoded by the hSNF5/INI1 gene on chromosome 22q11.2. Mutations in this gene are seen in ATRT. Cytogenetic studies often show monosomy or deletion of chromosome 22; however, this is not as specific or sensitive as IHC, since other tumors with complex karyotypes may show loss of 22 in addition to other events, and the INI1 gene may be mutated by a mechanism other than deletion (i.e. point mutations) not detectable by FISH or LOH studies. The presence of an hSNF5/INI1 gene mutation or loss of the INI1 protein expression by IHC is sufficient to confer a diagnosis of ATRT.

Answer 114

Positive for androgen receptors (75%), rarely for PR, and negative for ER. Other positive stains include beta-catenin, MSA, CD31 and CD34 in the vascular endothelium, and CD117 in mast cells.

Answer 115

All except for Gaucher disease type II.

Answer 116

MA is S100++, EMA-/+, ER/PR/HER2 -/-/-. TC is S100-, EMA++, ER/PR/HER2 +/+/-.

Answer 117

CS: Positive at the periphery and surrounding lumens for the 3 MEC makers, c-KIT neg. ACC: Positive at the periphery and in the basaloid cells with p63, negative for the other 2 MEC markers, and c-KIT pos. Cribriform DCIS: Positive at the periphery only for the 3 MEC markers, c-KIT neg. ICC: Negative for all.

Answer 118

Paget disease cells are almost always positive for CK7 and CAM5.2 (and are usually positive for HER2/neu).

Answer 119

Except for HER2/neu and mucicarmine negativity, Toker cells have the same immunoprofile as PD cells.

Answer 120

Renal medullary carcinoma shows loss of INI1, while the other two retain INI1 expression.

Answer 121

The most popular fixattive in pathology is formalin, an aqueous solution of formaldehyde gas, which is buffered to physiology pH by sodium phosphate (this is called neutral buffered formalin).

Answer 122

Neutral buffered formalin, although marketed as 10%, is actually ~4%, because it is 10% of a solution containing 37% formaldehyde gas.

Answer 123

Formaldehyde (CH2O) reacts with water to produce methylene glycol (CH4O2), a type of alcohol. The structure of methylene glycol is (HO-CH2-OH), allowing 1 molecule of formaldehyde to react with more than 1 protein, thereby crosslinking proteins.

Answer 124

Hematoxylin - water soluble. Eosin is not water soluble; in typical use, it is dissolved in alcohol, requing an alcohol rinse between the water soluble hematoxylin and eosin.

Answer 125

In IHC nomenclature, the term "CD" for "cluster of differentiation" or "cluster designation" is often used. Soon after monoclonal Abs were employed, it was recognized that there were groups of Abs that were made in different labs that reacted with the same Ag. It was difficult to know precisely which Abs reacted to which Ags, and to which epitopes on which Ags. Hence, the CD nomenclature was developed at the First International Workshop and Conference on Human Leukocyte Differentiation Antigens (HLDA) in Paris in 1982. It was decided that Ags that were well-characterized and that reacted to a group of Abs were to be considered members of the same CD. Typically, Ags of the same CD had slightly different epitopes that slightly different mAbs reacted to. For an Ag to receive a CD number, it must be well characterized and there must be at least 2 mAbs that will bind to it. If an Ag is reasonably well-characterized but falls short of the criteria for a CD designation (eg, only 1 mAb is known to bind to it), it may be denoted with a "w," as in "CDw198."

Answer 126

In the primary detection method, the primary antibody is directly labeled with the fluorochrome or enzyme. In indirect detection, a second Ab that is reactive to the first Ab is employed, and the detection fluorochrome or enzyme is attached to this second Ab. Because multiple secondary Ab molecules can bind to 1 primary Ab molecule, amplification of the signal can be achieved in an indirect system.

Answer 127

This method is based on secondary Abs that are attached to biotin. Avidin, a compound that binds biotin tightly, is conjugated to peroxidase and allowed to react to the biotin on the second Ab. If the target Ag is present, the first Ab will bind, then the secondary Abs, attached to biotin, will bind to the first Ab, and finally, the avidin-enzyme complex will bind to the biotin. This method permits appreciable amplification of signal. Streptavidin has largely replaced avidin b/c the latter molecule occasionally binds nonspecifically, and the use of streptavidin results in a lower background.

Answer 128

If diaminobenzidine (DAB) is used as the chromogen, a brown color results. If aminoethylcarbazole (AEC) is used, a red color results.

Answer 129

Both systems are a composite that takes into account both the percentage of cells that stain and the degree to which they stain. The H-score is obtained by counting multiple fields and determining whether the cells stain negatively (0), weakly (1+), moderately (2+), or strongly (3+). The percentage of cells at each staining intensity is determined and the H-score is obtained by the formula: H-score = (% cells at 1+ intensity) + 2x(% cells at 2+ intensity) + 3x(% cells at 3+ intensity). In the Allred system, the number of cells that stain is classified from 0 to 5. The intensity of staining is rated from 1 to 3. These 2 numbers are then added.

Answer 130

IHC positivity for tyrosine hydroxylase, which is the rate limiting enzyme in the synthesis of catecholamines, is very helpful to distinguish paragangliomas from other neuroendocrine carcinomas, which can also be negative for CKs. But the positivity is usually weaker and more variable, and sometimes absent in parasympathetic paragangliomas compared to sympathetic paragangliomas.

Answer 131

Loss of succinate dehydrogenase B expression if regarded as a surrogate marker for some of the familial paraganglioma syndromes caused by SDHx (x refers to all subunits, SDHA refers to subunit A, etc) mutations. Moreover, the use of SDHB Ab not only allows the identification of SDHx-related tumors, but also provides prognostic data, owing to the high rate of malignancy associated with SDHB-driven paragangliomas.

Answer 132

OCT3/4, also known as POU5F1, is a nuclear transcription factor interacting with other nuclear factors, such as NANOG, SOX2, SALL4, and KLF4, that maintain pluripotency in primordial germ and stem cells. It is expressed very early during embryogenesis and has an essential role in blastocyst differentiation.

Answer 133

OCT3/4 regularly shows positivity in dysgerminoma but can also be expressed in embryonal carcinoma and in some immature neural elements of ovarian teratoma. However, considering that EC is exceptionally rare in the ovary, OCT3/4 can be considered as a selective marker of ovarian dysgerminoma. OCT3/4 is particularly useful in demonstrating the primitive germ cell identity of poorly fixed tissue or microcystic cases, helping to differentiate them from small cell tumors and even struma ovarii. It also identifies isolated dysgerminoma cells masked by fibrosis or inflammation. Furthermore, it is particularly useful in the identification of the primary tumor in distant metastases.

Answer 134

SALL4 is a nuclear factor and a member of the family of SALL genes, which are involved in totipotency and are expressed at an early stage of embryogenesis.

Answer 135

SALL4 is a pluripotency marker strongly expressed by dysgerminomas, embryonal carcinoma, yolk sac (primitive endodermal) tumor, and primitive areas of immature teratoma; consequently, it represents a good, broad marker for MOGCTs. Nevertheless, its expression has also been shown in myeloid leukemia and in some gastric carcinomas.

Answer 136

CD2/CD3/CD4/CD5 pos, CD7/CD8 neg.

Answer 137

It is typically a mature cytotoxic T-cell lymphoma with a phenotype of CD4-, CD8+. Hemophagocytic syndrome is a frequent complication that when present usually precipitates a rapidly downhill clinical course.

Answer 138

The lymphoma cells show marked intrasinusoidal infiltration in the spleen, liver, and bone marrow; lymph node involvement is uncommon. The lymphoma cells are cytotoxic T-cells, usually of the delta-gamma receptor type, which express TIA-1 but are usually negative for perforin. The typical phenotype is CD2+, CD3+, CD7+, CD4-, CD5-, CD8- (usually). EBV is negative.

Answer 139

MPO stains the primary (azurophilic) granules indicative of granulocytic differentiation. Fine dusty positivity may be seen in monoblasts. It is negative in lymphoblasts, erythroblasts, and megakaryoblasts.

Answer 140

MPO degrades quickly in wet specimens, but is stable in smears for up to 1 month.

Answer 141

Granulocytic and monocytic cells.

Answer 142

The granulocytic series. Monocytes and lymphocytes are negative.

Answer 143

They stain cells of the monocytic series and, to variably lesser extents, megakaryocytic, lymphocytic, granulocytic, and erythroid series.

Answer 144

Nonspecific esterases (include alpha naphthyl acetate esterase and alpha naphthyl butyrate esterase) mainly stain cells of the monocytic series. Monocyte NSE activity is inhibited by sodium fluoride (NaF).

Answer 145

PAS is positive in most lymphoid and some myeloid blasts.

Answer 146

In ALL, it shows "block" positivity, often encircling the nucleus in a "rosary bead" fashion. In AML, when positive, it is usually a diffuse, granular positivity.

Answer 147

Naphthol AS-biphosphate.

Answer 148

Bands and neutrophils are scored on the intensity of cytoplasmic staining from 0 to 4+ until 100 cells are counted. The number resulting from the sum of the 100 values is reported as the LAP score. Normal adults score in the range of 40-120.

Answer 149

Peripheral blood or bone marrow smears are fixed and incubated in an alkaline-dye solution of naphthol AS-MX phosphate and fast blue RR salt or fast violet B salt. As a result of phosphatase activity, naphthol AS-MX is liberated and immediately coupled with a diazonium salt, forming an insoluble, visible pigment at the sites of phosphatase activity.

Answer 150

AKA BCL1 (B-cell leukemia/lymphoma 1) AKA PRAD1 (parathyroid adenomatosis 1). On 11q13.3. Encodes the cyclin D1. Mainly nuclear localization. No normal expression in lymphocytes.

Answer 151

BCL2 (B-cell leukemia/lymphoma 2) is located on 18q21.33. In normal and reactive lymph nodes, it is expressed by mantle cells and the small number of mantle cells that normally permeate the follicle center. It is an inhibitor of apoptosis (although there are other members of the bcl-2 family that are pro-apoptotic), so its expression is inhibited in germinal centers, where apoptosis forms part of the B-cell production pathway.

Answer 152

BCL6 (B-cell Lymphoma 6) AKA BCL5, LAZ3, ZBTB27, ZNF51, and BCL6A is located on 3q27.3. The gene product is a critical transcription factor responsible for normal secondary follicle formation during the germinal center reaction in lymphoid tissues and for proper T-cell-dependent Ab responses upon exposure to Ag. Accordingly, BCL6 is strongly expressed by germinal center B cells (GCBs) but is not present in naive or post-GCBs. BCL6 is thought to protect normal GCBs during the affinity maturation process (i.e., somatic hypermutation) in part by downregulating proapoptotic stimuli elicited by physiologic DNA double-strand breakage.

Answer 153

CD2 is a surface antigen that interacts with lymphocyte function-associated antigen (LFA-3) and CD48/BCM1 to mediate adhesion between T-cells and other cell types. It is expressed by T lymphocytes and NK cells, from a very early stage.

Answer 154

Cytoplasmic expression precedes surface expression and may be detectable by IHC (eg, in immature T cells and NK cells) when surface expression is not detected by flow cytometry.

Answer 155

A subset of T lymphocytes, specifically T helper/inducer cells. It is also expressed by monocytic (promonocyte and monocyte) and dendritic cells.

Answer 156

Occasionally, patients have increased polyclonal benign circulating CD19+/CD20+/CD5+ B cells, particularly in rheumatoid arthritis.

Answer 157

It is a T cell cell surface protein that plays an important role in T cell-B cell interaction in early lymphoid development. There is membrane expression early during T cell development, before TCR rearrangement; persists until terminal stages of T cell development. It is expressed by normal and neoplastic T cells and NK cells.

Answer 158

AKA MME (membrane metallo-endopeptidase), CALLA (Common Acute Lymphoblastic Leukemia Antigen), neutral endopeptidase 24.11, neprilysin, and enkephalinase. It is a cell membrane metallopeptidase which inactivates bioactive peptides.

Answer 159

Normal: PreB cells, preT cells, follicular center (germinal center) cells, granulocytes.

Answer 160

AKA ITGAX (integrin, alpha X (complement component 3 receptor 4 subunit)), CR4, MAC-1, SLEB6, and LeuM5. It is an integrin. Clears opsonized particles and immune complexes, and also binds to fibrinogen and is involved in adhesion of monocytes and neutrophils to endothelium and chemotaxis.

Answer 161

Normal: granulocytes, monocytes, NK cells, dendritic cells, 50% of activated CD4/CD8+ T cells. Disease: hairy cell leukemia (classic and variant), 81% of lymphoplasmacytic lymphoma, 50% of AML-M4 and M5.

Answer 162

AKA ANPEP (alanyl (membrane) aminopeptidase), APN, GP150, LAP1, P150, and PEPN. It has varied functions related to enzymatic degradation. It is a myeloid antigen, positive in granulocytic cells and precursors (but CD33 is more specific).

Answer 163

AKA lipopolysaccharide receptor and monocyte differentiation antigen. It is a GPI linked pattern recognition receptor that detects antigenic molecules on the surface of bacteria (lipoteichoic acid on gram positive, LPS on gram negative), myobacteria (glycolipids) and fungi (mannans), as part of the innate (non-adaptive) immune system (adaptive immune system refers to lymphocytes recognizing microorganism proteins via T cell receptors and antibodies).

Answer 164

AKA FUT4 (fucosyltransferase 4 (alpha (1,3) fucosyltransferase, myeloid specific)), Leu-M1, ELFT, LeX (Lewis X), SSEA-1. It is a carbohydrate that mediates phagocytosis and chemotaxis. Uses: Granulocytic marker. In Hodgkin lymphoma, there is membranous, diffuse cytoplasmic, or faint golgi-zone staining of Reed-Sternberg cells; this can be used to confirm diagnosis, or to differentiate Hodgkin lymphoma (CD15+) from ALCL (CD15-).

Answer 165

AKA FCGR3A (Fc fragment of IgG, low affinity IIIa, receptor (CD16a)), FCG3, FCGR3, IGFR3. It is used as an NK cell, granulocyte, and monocyte/macrophage marker.

Answer 166

AKA B4, CVID3. It forms a complex with CD21, CD81 and CD225 in the membrane of mature B cells and regulates B cell development, activation and differentiation. It is expressed by B cells (from the pre-B stage onward) and follicular dendritic cells.

Answer 167

CD19 is expressed by B cell from the pre-B stage onward and is positive in B cell lymphoma and leukemias, but it often weak/negative in FL and DLBCL. It may be present in some cases of AML, especially AML with t(8;21)(q22;q22).

Answer 168

Normal plasma cells are characterized by expression of bright CD38, CD138, CD27, dim CD45, and dim CD19. Typically, aberrant antigen profiles in neoplastic plasma cells include expression of CD28, CD56, CD20, CD117 (less commonly CD13, CD33, CD44, or CD49d), diminished CD27, diminished CD38, and the complete absence of CD19 and/or CD45.

Answer 169

A phosphoprotein expressed on the surface of B-cells (from late pro-B cells through memory cells; it is not expressed on early pro-B cells or plasma cells). It is encoded by the MS4A1 gene (membrane-spanning 4A gene family).

Answer 170

Antibody FMC-7 appears to recognise a conformational variant/epitope of CD20, also known as the FMC-7 antigen. Cells with weak CD20 tend to be FMC-7 negative, while cells with bright CD20 tend to be FMC-7 positive.

Answer 171

AKA B lymphocyte cell adhesion molecule (BL-CAM), Sialic acid binding immunoglobulin-like lectin/Siglec-2. It is considered a pan-B-cell marker. Is present on the surface of mature B cells and to a lesser extent on some immature B cells.

Answer 172

It is a C-type lectin that is the "low affinity" IgE receptor. It acts as a B cell growth and activation factor, promoting differentiation into plasma cells.

Answer 173

CD21, CD23 and CD35 are dendritic cell markers.

Answer 174

AKA IL-2 receptor alpha chain, IL2RA and TAC antigen.

Answer 175

AKA Ki-1, Ber-H2, and TNFRSF8. Is a cell membrane protein of the tumor necrosis factor receptor family and tumor marker. Is found on normal plasma cells and activated T and B cells. In hematologic malignancy, CD30 (along with CD15) expression is the hallmark of Reed-Sternberg cells in classic Hodgkin lymphoma. It is also found on ALCL. Expression of CD30 (usually focal) is a characteristic feature of mediastinal-type DLBCL.

Answer 176

A transmembrane protein that is a member of the SIGLEC (sialic acid-binding immunoglobulin-like lectin) family of lectins. It is not expressed outside the hematopoietic system. Is classically considered a myeloid marker (along with CD13), but can be expressed in some lymphoid cells. Is positive in almost all AML M0, and in ~80% of AML M1-M5.

Answer 177

It is a cell surface glycoprotein and functions as a cell-cell adhesion factor. In hematology, is a marker of hematopoietic progenitor cells/hematogones/blasts.

Answer 178

AKA ADP-ribosyl cyclase 1/cyclic ADP ribose hydrolase. A glycoprotein that is a multifunctional enzyme. Is associated with a poor prognosis in CLL/SLL.

Answer 179

AKA TNF receptor superfamily member 5. Is a costimulatory protein found on antigen presenting cells and is required for their activation. Hematologically, it is expressed by antigen presenting cells (dendritic cells, macrophages, B cells) as well as neoplastic B cells.

Answer 180

AKA platelet glycoprotein IIb, GPIIb, platelet fibrinogen receptor alpha subunit. In hematology, positivity is seen in platelets, megakaryocytes, and hematopoietic progenitor cells (erythroid, myeloid, megakaryocytes). It is also seen in AML M7 and blasts in transient myeloproliferative disorder.

Answer 181

Integrin alpha-IIb (CD41) is a protein that is encoded by the ITGA2B gene. Integrin beta-3 (CD61) is a protein that is encoded by the ITGB3 gene. Alpha-IIb undergoes post-translational cleavage to yield disulfide-linked light and heavy chains that join with beta-3 to form a fibrinogen receptor expressed in platelets that plays a crucial role in coagulation. Mutations that interfere with this role result in thrombasthenia.

Answer 182

AKA leukosialin or sialophorin. Is a transmembrane cell surface protein that is encoded by the SPN (SialoPhoriN) gene. Is a pan-T-cell marker present on normal and neoplastic T-cells, but is also present on normal and neoplastic granulocytes and some B-cells.

Answer 183

CD43 (AKA sialophorin or leukosialin) is defective or deficient in lymphocytes of patients with Wiskott-Aldrich syndrome. Wiskott-Aldrich syndrome is an X-linked recessive immunodeficiency characterized by thrombocytopenia, eczema, and recurrent infections.

Answer 184

AKA leukocyte common antigen (LCA), or "protein tyrosine phosphatase, receptor type, C" (PTPRC). Is an enzyme that is encoded by the PTPRC gene and is found in nearly all normal and neoplastic leukocytes. However, dim to absent CD45 (usually with strong CD34) is the immunophenotypic signature of myeloblasts, and dim to absent CD45 (with strong CD38) is indicative of plasma cells. Also, CD45 is not expressed in Reed-Sternberg cells (except NLPHD).

Answer 185

AKA N-CAM (neural cell adhesion molecule). It is a homophilic binding glycoprotein that contributes to cell-cell or cell-matrix adhesion during development. It is the prototypic markers of NK cells, but also stains other hematologic cells.

Answer 186

AKA Leu7, HNK1 (human natural killer-1), beta-1,3-glucuronyltransferase 1, and glucuronosyltransferase P. Is a glycoprotein enzyme encoded by the B3GAT1 gene that has cell adhesion functions. It is expressed by a subset of normal and neoplastic NK cells, among others.

Answer 187

AKA protectin, complement regulatory molecule, MAC-inhibitory protein (MAC-IP), or membrane inhibitor of reactive lysis (MIRL). Regulates complement mediated cell lysis by inhibiting formation of membrane attack complex (MAC); binds to C8 or C9 components, preventing incorporation of multiple copies of C9 required for complete formation of osmolytic core. It is present on nearly all human cells. Decreased cell surface expression, along with decreased CD55 - DAF, is a feature of the affected clone in paroxysmal nocturnal hemoglobinuria.

Answer 188

Genetic defects that reduce both CD55 and CD59 on erythrocytes produce PNH.

Answer 189

Genetic defects that reduce both CD55 and CD59 on erythrocytes produce paroxysmal nocturnal hemoglobinuria.

Answer 190

AKA KP1, macrosialin. Is a glycoprotein which binds to low density lipoprotein. It is used as a marker of histiocytes and histiocytic tumors, but its specificity is poor, because CD68 is specific to lysosomes, not cell lineage.

Answer 191

CD79 is a transmembrane protein that forms a complex with the B-cell receptor and generates a signal following recognition of antigen by the BCR. CD79 is composed of two distinct chains called CD79A and CD79B (formerly known as Ig-alpha and Ig-beta); these form a heterodimer on the surface of a B cell stabilized by disulfide bonding. CD79a and CD79b are both members of the Ig superfamily. Human CD79a is encoded by the mb-1 gene that is located on chromosome 19, and CD79b is encoded by the B29 gene that located on chromosome 17. Both CD79 chains contain an immunoreceptor tyrosine-based activation motif (ITAM) in their intracellular tails that they use to propagate a signal in a B cell.

Answer 192

Can be used in ALL or small B cell lymphoproliferative disorders when CD20 may be negative or after rituximab (anti CD-20) therapy. Can be used in infarcted lymphomas. Can be used to differentiate preB lymphoblastic lymphoma from Ewing’s sarcoma.

Answer 193

AKA p30/32, MIC2, O13, T cell surface glycoprotein E2, single-chain type-1 glycoprotein. It is part of the Xg blood group system. Positive staining in numerous normal cell types as well as tumors.

Answer 194

AKA human mucosal lymphocyte antigen 1, integrin alpha E beta 7, ITGAE. Stains normal and tumor intraepithelial T lymphocytes. Will stain hairy cell leukemia, enteropathy-associated T cell lymphoma, and some splenic marginal zone lymphomas.

Answer 195

AKA (proto-oncogene) c-kit, tyrosine-protein kinase Kit, mast/stem cell growth factor receptor (SCRFR). It is a receptor for kit protein, a 145 kD tyrosine kinase growth factor receptor protein important for development and survival of mast cells, hematopoietic stem cells, melanocytes, germ cells, and interstitial cells of Cajal. The gene is at 4q11-21, adjacent to PDGFRA.

Answer 196

AKA heparan sulfate proteoglycan, syndecan-1. It is a very specific marker of plasma cells within hematolymphoid proliferations, but is positive in a wide range of epithelial and mesenchymal proliferations.

Answer 197

It is a glycoprotein implicated in apoptosis and other cellular functions. Is strongly expressed in follicular dendritic cell tumors, weak/no expression in other dendritic cell tumors. Positive in ALCL in a discrete golgi pattern (80-100% of systemic cases, 40-60% of primary cutaneous cases). Cytoplasmic positivity in DLBCL (12%); carcinomas of breast, colon, pancreas, prostate; megakaryocytes.

Answer 198

AKA CD227; episialin; Mucin 1, cell surface associated (MUC1); polymorphic epithelial mucin (PEM). Is a large cell surface mucin glycoprotein expressed by most glandular and ductal epithelial cells and some hematopoietic cells. Normally acts as barrier to apical surface of epithelial cells, playing a protective and regulatory role. Shed into the bloodstream of adenocarcinoma patients, used in commercial serum tumor marker assays (CA15-3).

Answer 199

Actin bundling/cross-linking protein with important role in cell motility and adhesion. It is expressed by RS cells and dendritic reticulum cells.

Answer 200

The proper interpretation of Congo red stains requires thick tissue sections (10 um). Thin sectioning at routine 3-5 um can result in erroneous Congo red negativity.

Answer 201

While IHC with specific antibodies can be used for amyloid subtyping, pre-incubation of Congo red-stained sections with kalium-permanganate causes the fibrils in AA amyloidosis to lose their affinity to Congo red. Thus, this can be used to identify amyloid deposits of the AA type.

Answer 202

EBV-encoded RNA; nuclear RNA portions of EBER 1 and 2 genes. Nuclear stain.

Answer 203

EBER is located to the nuclei of RS/H cells, with little to no expression in the background small lymphocytes. LMP1 is expressed in the cytoplasm and surface membrane of RS/H cells but is rarely expressed in latently infected background lymphocytes of Hodgkin lymphoma.

Answer 204

Acute disseminated encephalomyelitis is an acute postviral or postvaccinal demyelinating disease. The typical lesion seen is a perivenular demyelination.

Answer 205

TEM typically exhibits diffuse cytoplasmic staining, while AIS is negative with rare exceptions. Of note, normal endocervical glands may show minimal vimentin expression confined to the basal cytoplasm along with delicate lateral staining of the cell borders.

Answer 206

The Ab recognizes the DNA binding neuron-specific protein NeuN (NEUronal Nuclei). Positive normal staining is seen in mature postmitotic neurons. Positive staining in disease is seen in epithelioid GBMs (100%), central neurocytomas (87%), supratentorial pediatric ependymoma, neuroendocrine carcinoma (50-90%), and amyloid bodies. No/reduced NeuN expression is associated with immature/diseased neurons. Negative staining in cerebellar Purkinje cells and Golgi cells, olfactory Mitral cells, retinal photoreceptors, pilocytic astrocytoma and oligodendroglioma. Negative/weak staining seen in neurons of substantia nigra.

Answer 207

100% of blastic mantle cell lymphoma, 90% of mantle cell lymphoma, 25-70% of hairy cell leukemia, 40% of plasma cell myeloma. 10% of CLL/SLL, 8% of plasmacytoma, 4% of classical Hodgkin disease, 2% of DLBCL.

Answer 208

Leishmania has discrete organisms with a nucleus and kinetoplast bound by a membrane; PAS negative. Histoplasma has a more amorphous look, some (but not all) are budding; PAS positive.

Answer 209

Classic Hodgkin lymphoma: LCA neg, CD20 neg, CD15 pos, CD30 pos, EMA neg, bcl-6 neg, vimentin pos. NLP Hodgkin lymphoma: LCA pos, CD20 pos, CD15 neg, CD30 neg, EMA pos, bcl-6 pos, vimentin neg.

Answer 210

Glycogen. So the cytoplasm will be PAS+ diastase sensitive.

Answer 211

CD136 in 100%. S100 in 93%. CK8 in 92%. PAX-8 in 91%. CD117 in 90%. Parvalbumin in 79%. CK18 in 77%. EMA/MUC1 in 74%. PAX-2 in 62%. Vimentin in 56%.

Answer 212

Desmin, actin, and cytokeratin.

Answer 213

Smears of blood or bone marrow specimens stained with Wright or Giemsa reagents show Erlichia organisms as round or oval violet bodies, about 1 um in diameter, in the cytoplasm of neutrophils, lymphocytes, monocytes, and macrophages. Clusters of organisms (morulae) can be seen. The bone marrow usually shows erythrophagocytosis and a decrease in myeloid cells and megakaryocytes. In tissue sections, the organism is best seen with Brown-Hopps stain.

Answer 214

Silver stains, such as Steiner, Dieterle, and Warthin-Starry.

Answer 215

Myeloid or monocytic blasts are typically weakly positive or negative with PAS. A granular (may be a finely diffuse pattern or a coarse block pattern) PAS pattern with a negative background is characteristic of lymphoblastic leukemia. PAS staining is positive in the erythroid population in erythroblastic leukemias.

Answer 216

Both. It is at least as sensitive as GMS staining, less technically demanding to perform, and, in most cases, much easier to evaluate.

Answer 217

True. Although cytomegalic changes are generally easily identified, they may be obscured by inflammation, and in some settings such as AIDS, not be well developed, in which case IHC or ISH improves detection of CMV infection.

Answer 218

DF is CD34 neg. DFSP lesional cells exhibit diffuse and strong CD34 expression.

Answer 219

The lesional cell of thymomas is the epithelial cell, which stains with various panCK Abs, as well as Abs to high (34BetaE12) and low (Cam5.2) molecular weight Abs. In addition, most thymomas are p63 positive. Lymphocytes with a thymic phenotype (CD3+, CD1a+, TdT+, CD99+) are present in these tumors, even when they metastasize. CD5 and KIT are expressed by the majority of thymic carcinomas, and only occasionally by thymomas. CD20+ lymphocytes may predominate in micronodular thymomas with lymphoid hyperplasia, and CD20 also stains spindle-shaped thymoma cells, which are also CK+.

Answer 220

Negative for both. Only 16% are CK7 positive, and only 8% are CK20 positive.

Answer 221

CK7+ and CK20+/-. 92% are CK7 positive, and 63% are CK20 positive.

Answer 222

CK7+ and CK20-. 97% are CK7 positive, and only 7% are CK20 positive.

Answer 223

CD31 in 100%, HMB-45 in 95%, SMA in 88%, melan-A in 86%, mart-1 in 75%, vimentin in 69%, MITF in 65%, desmin in 55%, tyrosinase in 31%, S100 in 29%, panCK in 0%.

Answer 224

MCCs are unique in that they possess both neuroendocrine and epithelial features. They are positive for epithelial markers such as AE1/AE3, CAM 5.2, panCK, EMA, and Ber-EP4. Also, CK20 is a fairly specific and sensitive marker for MCC, with a characteristic paranuclear dotlike positivity. They are positive for neuroendocrine markers such as chromogranin, synaptophysin, NSE, neurofilaments, bombesin, somatostatin, VIP, and proconvertases PC1/PC3 and PC2. MCC may also express CD117, CD56, and rarely CD99 and TdT. MCC is negative for TTF-1, S100, and LCA.

Answer 225

The characteristic histomorphology is the presence of a large amount of intracellular and extracellular, eosinophilic secretions that are positive for PAS-D. Most tumors are positive for S100, alpha-lactalbumin, and E-cadherin, and negative for ER/PR/HER2, GCDFP-15/BRST-2, and mCEA. In addition, some secretory carcinomas demonstrate a basal-like immunoprofile (positivity for CK5/6, CK14, CK17, CD117, EGFR, and vimentin).

Answer 226

Papillary carcinoma (92% positive for galectin-3, 86% positive for CK19, 77% positive for HBME-1). Papillary carcinoma, macrofollicular variant (100%, 86%, 100%). Papillary carcinoma, follicular variant (90%, 89%, 90%). Follicular adenocarcinoma (66%, 59%, 62%).

Answer 227

Atypical follicular adenoma (90% positive for galectin-3, 14% positive for CK19, 29% positive for HBME-1). Hyalinizing trabecular tumor (86%, 38%, 0%). Hurthle cell adenocarcinoma (86%, 39%, 20%). Anaplastic carcinoma (74%, 25%, 7%). Hurthle cell adenoma (60%, 0%, 33%).

Answer 228

Galectin-3 positive in 20%, CK19 positive in 87%, and HBME-1 positive in 19%.

Answer 229

Well differentiated thyroid tumor of uncertain malignant potential (37% positive for galectin-3, 33% positive for CK19, 40% positive for HBME-1). Nodular goiter (19%, 37%, 3%). Follicular adenoma (18%, 32%, 11%). Papillary hyperplastic nodule (13%, 25%, 0%). Thyroid nodule hyperplasia (10%, 24%, 0%). Thyrotoxic hyperplasia (7%, 9%, 0%).

Answer 230

0% positive for galectin-3, 20% positive for CK19, 0% positive for HBME-1.

Answer 231

MSH2-, MSH6-, MLH1+, PMS2+.