Histo Lab Flashcards
What 2 CK immunostains can be used to distinguish cholangiocarcinoma and hepatocellular carcinoma?
CK7 and CK19. Cholangiocarcinoma is CK7+ CK19+, while hepatocellular carcinoma is CK7- CK19-.
What % of colorectal adenocarcinomas express nuclear CDX2 and apical/luminal/cytoplasmic villin?
Nearly 100%.
What are 2 specific immunostains for lymphatic endothelium?
D2-40 (AKA M2A or podoplanin) and LYVE-1.
What are 3 panendothelial markers?
Factor VIII (von Willebrand factor), CD31, CD34.
What are some carcinomas that stain with vimentin?
Renal cell carcinoma, endometrial adenocarcinoma, salivary gland carcinoma, follicular thyroid carcinoma.
What are the 5 major groups of tissue fixatives?
The 5 major groups of fixatives are classified according to mechanism of action, and are the aldehydes, mercurials, alcohols, oxidizing agents, and picrates. The aldehydes include formalin and glutaraldehyde. Formalin: An aqueous solution of formaldehyde gas that penetrates tissue well but relatively slowly; the standard solution is 10% neutral buffered formalin. A buffer prevents acidicty that would promote autolysis and cause precipitation of formol-heme pigment in the tissues. Tissue is fixed by cross-linkages formed in the proteins, particularly between lysine residues. This cross-linking does not harm the structures of proteins greatly, preserving antigenicity, and is therefore good for immunoperoxidase techniques. Glutaraldehyde: The standard solution is a 2% buffered glutaraldehyde and must be cold, buffered, and not more than 3 months old. Fixes tissue quickly and therefore is ideal for EM. Causes deformation of alpha-helix structure in proteins and therefore is not good for immunoperoxidase staining. Penetrates poorly but gives best overall cytoplasmic and nuclear detail. Tissue must be as fresh as possible and preferably sectioned within the glutaraldehyde at a thickness of no more than 1 mm to enhance fixation. The mercurials include B-5 and Zenker. They contain mercuric chloride and must be disposed of carefully. Penetrate poorly and cause tissue hardness but are fast and give excellent nuclear detail. Best application is for fixation of hematopoietic and reticuloendothelial tissues. The alcohols include methyl alcohol (methanol) and ethyl alcohol (ethanol). They are protein denaturants. Not used routinely for tissue because they dehydrate, resulting in tissues’ becoming brittle and hard. Good for cytologic smears because they act quickly and give good nuclear detail. The oxidizing agents: include permanganate fixatives (potassium permanganate), dichromate fixatives (potassium dichromate), and osmium tetroxide cross-link proteins. Cause extensive denaturation. Some of these have specialized applications but are used infrequently. Picrates: Bouin solutaion has an unknown mechanism of action. It does almost as well as mercurials with nuclear detail but does not cause as much hardness. Picric acid is an explosion hazard in dry form. Recommended for fixation of tissues from testis, GI tract, and endocrine organs.
What are the internal diameters for 18, 16, and 14 gauge needles?
18 gauge, 300-400 um. 16 gauge, 600-700 um. 14 gauge, 900-1000 um.
What are typical staining patterns for CK7, CK20, CD10, and RCC in oncocytoma, chromophobe renal cell carcinoma, and clear cell renal cell carcinoma.
Oncocytoma: CK7 neg, ~25% are CK20 pos, ~30% are CD10 pos, RCC neg. Chromophobe renal cell carcinoma: CK7 pos, CK20 neg, 0 to 45% are CD10 pos, RCC neg. Clear cell renal cell carcinoma: CK7 neg, CK20 neg, CD10 pos, RCC pos.
What do GISTs stain + for?
CD117 (c-kit) (>95%), and may stain + for CD34, SMA, desmin, nestin, and S100. DOG-1 (Discovered On GIST-1)/PDGFR-alpha is useful for c-kit negative GISTs. Up to 47% of small bowel GISTs and 10-14% of rectal and esophageal GISTs stain for SMA.
What do steroid-secreting cells stain + for?
Inhibin.
What does CK AE1/AE3 cocktail stain, and what are it’s uses in prostate?
CK AE1/AE3 cocktail detects acidic (CK10, CK14-16, and CK19) and basic (CK1-CK6 and CK8) cytokeratins. Is useful in the DDx of nonspecific granulomatous prostatitis, crushed or marked inflammation, or xanthoma cells versus Gleason pattern 5 prostate carcinoma. Is also useful in diagnosing small cell proliferations in the prostate, such as small cell carcinoma, lymphoma, and rhabdomyosarcoma. In the posttreatment setting, is helpful in highlighting individual atrophic prostate cancer cells and is superior to PSA, which can be suppressed by therapy and is, therefore, not detectable by IHC posttreatment.
What fixative and stain is used for bone marrow aspirate smears?
After the spread aspirate smears are allowed to air dry, they are fixed in methanol then stained with May-Grunwald-Giemsa or Wright stains.
What immunostain reacts with the endothelium of cerebral capillaries, placental vasculature, and juveline capillary angiomas?
GLUT-1.
What is CD117/c-kit?
A transmembrane TK receptor involved in mitogenic signaling. Stains GISTs in a strong, diffuse, pancytoplasmic, and sometimes membranous pattern. Some GISTs show a cytoplasmic “dotlike” pattern, and these are more likely to be extraintestinal or show epithelioid morphology. CD117 also stains mast cells, some hematopoietic precursor cells, melanoma, renal cell carcinoma, and seminoma.
What is the most useful immunostain for desmoid-type fibromatosis?
Beta-catenin, which is involved in Wnt and E-cadherin signaling pathways, which play a role in tumorigenesis. In certain neoplasms, beta-catenin accumulates in the cytoplasm and aberrantly translocates to the nucleus when there is dysregulation of these pathways. As beta-catenin accumulates in the nucleus, it activates oncogenes. With beta-catenin IHC, only nuclear staining should be considered positive. Beta-catenin stains 71-100% of desmoid-type fibromatosis, but focal positivity can cause false negatives in needle core biopsies. Up to 24% of solitary fibrous tumors stain with beta-catenin, but these 2 entities are morphologically distinct.
What is the PAX-2 marker?
The PAX-2 marker is a renal-restricted nuclear transcription factor expressed in 70-80% of metastatic clear cell RCC.
What is the RCC marker?
The RCC marker is a glycoprotein found in the brush border of the proximal tubules of the kidney. It is + in 47-85% of clear cell RCC and 60-90% of papillary RCC.
What stain is used for blood smears?
Romanowsky first used in 1890 a mixture of eosin and methylene blue. Subsequent modifications are May-Grunwald-Giemsa and Wright stains. Both contain eosin and methylene azures, which are derivatives of methylene blue.
Which immunostain is + in ductal breast carcinoma and - in lobular breast carcinoma?
E-cadherin.
What are hematopoietic markers for identification of myeloblasts? Give patterns of CD34, TdT, CD10, c-kit, HLA-DR, sIg, and lineage specific markers.
CD34 +/-, TdT - (rarely + in M0), CD10 - (rarely +), c-kit +/-, HLA-DR +/-, sIg -. Lineage specific markers: CD13, CD33, CD15, CD11b, c-kit. CD34 and/or c-kit are typically present in AML, although some forms of AML may be entirely negative for CD34 and c-kit, notably AML with monocytic differentiation. Most AMLs express HLA-DR, but some myeloid leukemias (i.e. acute promyelocytic (M3) and AML with NPM1 mutations and cup-like nuclear invaginations) are HLA-DR negative. Myeloid sarcoma (chloroma) can be identified by immunostains for blast markers (CD34, c-kit), myeloid/monocytic markers (MPO, lysozyme) and CD43.
What are hematopoietic markers for identification of B-lymphoblasts? Give patterns of CD34, TdT, CD10, c-kit, HLA-DR, sIg, and lineage specific markers.
CD34 + (may be -), TdT +, CD10 + (occasionally -), c-kit -, HLA-DR + (rarely -), sIg - (or dim +). Lineage specific markers: CD19, CD79a, CD20 (+/-). DDx: Burkitt lymphoma has a mature B cell phenotype (sIg+, kappa or lambda +, CD20+, CD10+, Bcl-2 -) and is negative for blast markers (CD34, TdT).
What are hematopoietic markers for identification of T-lymphoblasts? Give patterns of CD34, TdT, CD10, c-kit, HLA-DR, sIg, and lineage specific markers.
CD34 +/-, TdT +, CD10 +/-, c-kit - (very rarely +), HLA-DR - (rarely +), sIg -. Lineage specific markers: CD3 (often cytoplasmic only).
All LGBCLs are positive for what hematopoietic markers?
CD45, pan-B markers CD19/20/22/79a and sIg.
What is typically seen on flow cytometry for CLL/SLL, MCL, FL, MZL, LPL, and HCL?
CLL/SLL: small FMC7- B-cells, light chain dim, CD20 dim. MCL: small FMC7+ B-cells, light chain bright, CD20 bright. FL: small-medium size light chain restricted CD10+ B-cells. MZL: often mixture of neoplastic and non-neoplastic B-cells; may be CD23+. LPL: light chain restricted small B-cells + plasma cells. HCL: CD20 bright, CD22 bright, CD103+, CD11c+, CD25+; very few monocytes in PB or BM.
What are PAX2 and PAX8 and what can they be used for?
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.
Alpha-methylacyl coenzyme a racemase (AMACR).
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.
TFE3, TFEB, and cathepsin-K immunostains. What renal tumors do they stain?
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.
What are 4 markers that are expressed in a high percentage of urothelial carcinomas but are not usually expressed in RCCs?
Uroplakin III, p63, thrombomodulin, and GATA3.
___ (an immunostain) is a useful marker for the diagnosis of metanephric adenoma.
CD57 (an immunostain) is a useful marker for the diagnosis of metanephric adenoma.
Are testicular seminoma and embryonal carcinoma closely related entities?
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.
How do seminomas and embryonal carcinomas stain with CK AE1/AE3, CD30, CD117, podoplanin (D2-40), SOX2, and SOX17?
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.
What immunostain and pattern is characteristic of papillary clear cell RCC?
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).
Myogenin and MyoD1 stain (skeletal/smooth) muscle.
Myogenin and MyoD1 stain skeletal muscle.
Solitary fibrous tumors have a unique staining pattern, staining with (3 stains).
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”.
What are the differences between the Ziehl-Neelsen, Kinyoun, and Fite acid-fast stains?
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.
What are some organisms that stain AFB+?
Mycobacteria, Nocardia, Corynebacteria, Cryptosporidium, Microsporidium, Isospora, Cyclospora, Sarcocystis, Legionella micdadei, Rhodococcus equi, Saccharomyces.
Hep-Par 1, MOC31, p-CEA, and GPC-3 stains for diagnosis of HCC and differentiation from adenocarcinomas.
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.
What are the differences in staining pattern of CK20, CD44, and p53 for normal urothelium, reactive urothelium, and urothelial CIS?
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.
What are von Hansemann cells?
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.
How does small cell carcinoma of the bladder differ from small cell carcinoma in other body sites in regard to immunohistochemical staining?
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.
Does Merkel cell carcinoma stain with TTF-1?
No.
Lynch syndrome has mutations in what genes?
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.
What antibody panel is typically used for mismatch repair detection for Lynch syndrome?
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.
For testing for Lynch syndrome, most labs have an MMR-IHC panel consisting of antibodies to four MMR proteins: MLH1, MSH2, MSH6, and PMS2. Why do some advocate primary screening with only 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.
How is the MMR-IHC panel for Lynch syndrome testing interpreted?
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.
Both pancreatic endocrine neoplasms and solid pseudopapillary neoplasms are positive for what 2 immunostains?
CD56 and synaptophysin.
What is spirochetosis?
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.
Microglandular adenosis in the breast. Positive and negative immunostains?
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.
How can you differentiate microglandular adenosis from tubular carcinoma in the breast?
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-.
How do carcinoid tumors of pulmonary, gastric and duodenal, ileal, appendiceal, and rectal types stain with TTF-1, CDX-2, and PDX-1 (Pancreatic and Duodenal Homeobox factor-1)?
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.
What staining patterns for PAS, PAS-D, TFE3, muscle markers, cytokeratin, EMA, GFAP, synaptophysin, and S100 are seen in alveolar soft part sarcoma?
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.
Mesenchymal hamartoma of liver.
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.
The diffuse cytoplasmic positivity of chromophobe renal cell carcinoma with Hale’s colloidal iron stain is due to __.
The diffuse cytoplasmic positivity of chromophobe renal cell carcinoma with Hale’s colloidal iron stain is due to staining of acid mucopolysaccharides.
What is the classic morphologic appearance, immunophenotype, and cytogenetic abnormality seen in Burkitt lymphoma?
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.
Immunostains for endometrial stromal sarcoma.
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.
What immunostain can be used to differentiate paragangliomas from neuroendocrine tumors?
Cytokeratin. Paragangliomas generally do not stain with cytokeratins.
What are the PAX2 and PAX8 genes, what is their utility as immunostains?
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.
What are adenosine triphosphate stains used on muscle for?
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.
Hemangioblastomas. Histologic appearance and IHC.
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.
Sclerosing hemangioma/pneumocytoma of the lung. IHC characteristics?
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.
Sclerosing hemangioma/pneumocytoma of the lung is IHC positive for __ and __, the combination of which is generally diagnostic.
Sclerosing hemangioma/pneumocytoma of the lung is IHC positive for cytokeratin and TTF-1, the combination of which is generally diagnostic.
Intrapulmonary solitary fibrous tumor.
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.
What are pulmonary minute meningothelial nodules?
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.
What is the “fake fat phenomenon” that can be seen in mesothelial proliferations?
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.
What immunostain is useful to distinguish complete hydatidiform mole from partial hydatidiform mole?
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.
How does a hydropic abortus differ from a complete hydatidiform mole?
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.
IHC antibodies are classified as Class __ medical devices.
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.
IHC for Kaposi sarcoma.
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.
Spermatocytic seminomas are composed of what 3 cell types? Do they stain with PLAP and OCT3/4?
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.
Stains for juvenile granulosa cell tumor.
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.
Synovial sarcoma and TLE-1.
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.
Stains for Brenner tumor vs. transitional cell carcinoma of the ovary?
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.
IHC for MPNST.
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.
Clear cell sarcoma overview.
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.
How are podoplanin and D2-40 different?
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.
Ki-67 protein and antibodies against it.
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.
Stains for solid-pseudopapillary neoplasm of the pancreas.
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.
How to differentiate pancreatic neuroendocrine tumor from pancreatic solid-pseudopapillary neoplasm.
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.
Grossing and processing of endomyocardial biopsies.
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.
What sectioning methods and stains are used for endomyocardial biopsies?
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.
How should vascular grafts and stents be grossed and processed?
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.
What is the significance of the five common staining combinations seen in DNA mismatch repair protein IHC (MLH1, PMS2, MSH2, MSH6) in CRC? Give the MSI phenotype, clinical interpretation, and etiology.
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.
What FISH and IHC studies are useful in mantle cell lymphoma?
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.
Cytogenetic and IHC characteristics of hibernoma?
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.
From the LAST (Lower Anogenital Squamous Terminology Standardization) Project, when is p16 staining recommended?
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).
Positive p16 staining is defined as ___.
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.
Undifferentiated endometrial carcinoma.
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.
How can undifferentiated/dedifferentiated endometrial carcinoma be distinguished from endometrial adenocarcinoma FIGO grade 3? Comment on mean age at presentation, high stage (stage III/IV) %, growth pattern, glands, cords and trabeculae, cohesive growth, component demarcation, rhabdoid cells, myxoid matrix, IHC for panCK, IHC for EMA, and IHC for ER/PR.
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.
Adenoid cystic carcinoma in the breast. It has cribriform, solid, trabecular and basaloid patterns, two types of cavities and two types of cells. What are the two types of cavities and two types of cells?
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.
What are some atypical immunophenotypic features seen in CLL/SLL that correlate with atypical morphology, an unmutated IgVH gene, and a worse prognosis?
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.
Pulmonary enteric adenocarcinoma and how to differentiate from metastatic colorectal adenocarcinoma.
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.
How to differentiate reactive follicular hyperplasia from follicular lymphoma?
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.
IHC useful in liver and liver lesions.
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.
Steroid cell tumor, NOS of the ovary overview.
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.
___ deletions are detected in ~70% of atypical teratoid/rhabdoid tumors; however, loss of the corresponding ___ protein is even more common than the genetic alteration. Loss of ___ nuclear immunoreactivity in tumor cells is used as a surrogate for genetic testing to demonstrate biallelic inactivation of the gene.
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.
Isocitrate dehydrogenase (IDH1/IDH2) mutations have been detected in the majority of diffuse gliomas, with the notable exception of ___, 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.
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.
What IHC stains are positive in microglia?
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.
What histochemical stains can be done for oncocytes?
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.
Myoepithelioma of salivary gland. Micro. IHC. DDx.
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.
Pleomorphic adenoma. Micro.
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).
Basal cell adenoma in salivary gland. Epidemiology. Micro. IHC. DDx.
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.
Warthin tumor. Micro. IHC. Cytogenetics. DDx.
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.
Canalicular adenoma of salivary gland. Epidemiology. Micro. IHC. DDx.
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.
Lymphadenoma and sebaceous lymphadenoma of salivary gland. Micro. IHC. DDx.
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.
