Ch. 12 - Lymph Node Flashcards
What lymph nodes are good candidates for needling?
Superficially located, >1cm, and unlikely to be reactive (eg young adults/children).
What are the limitations of FNA evaluation of lymph nodal pathology?
No architectural or vascular patterning (required for several lymphoma and benign LAD diagnoses), chance for sampling error.
What studies are usually required for subclassing lymph node pathology?
Immunophenotyping (flow is better than immunocytochemistry), molecular studies. Be sure to dedicate material for these ancillary studies.
Recall (all of!) the normal cellular components of a lymph node.
T-cells, B-cells (incl. centrocytes, centroblasts, immunoblasts), plasma cells, FDCs, IDCs, TBMs, sinus histiocytes, endothelial cells, mast cells & eosinophils.
Describe the cytology of normal lymph node.
Dispersed isolated cells, maybe with some intact follicles. Lymphoglandular bodies (fragments of lymphoid cytoplasm).
Which benign lymphadenopathies cannot generally be identified by FNA?
Castleman disease, PTGC, Toxoplasma (if lucky, may see organism in histiocytes), HIV lymphadenopathy, dermatopathic lymphadenitis.
Describe the cytology of Sarcoidosis
Epithelioid histiocytes, multinucleated giant cells, and a clean background. Note “boomerang/footprint” nuclei.
What fungal organisms may be reliably diagnosed on lymph node FNA?
Cryptococcus, histoplasma, coccidioides
Describe the cytology of cat scratch disease.
Granulomas, neutrophils, necrosis. Non-specific.
Describe the cytology of mycobacterial lymphadenitis.
Granulomas, neutrophils, necrosis. Look for “negative image” organisms as they resist staining.
Describe the cytology of Rosai-Dorfman disease.
Small lymphocytes emperipolesed within large histiocytes (S100+, CD68+).
Describe the cytology of Kikuchi lymphadenitis.
Necrotic debris, karyorrhexis, and cytoplasmic tingible bodies. No neutrophils! Crescentic histiocytes.
Describe the cytology of Infectious mononucleosis.
Increased percentage of immunoblasts and plasmacytoid lymphocytes. Atypical looking.
Describe the cytology of classic Hodgkin lymphoma.
Rare scattered Reed-Sternberg cells in a variable inflammatory infiltrate. May be hypocellular (nodular sclerosing). Not ideally diagnosed by FNA…
Describe the cytology of NLPHL.
Very hard to diagnose; look for enlarged popcorn cells in a mixed background.
Describe the cytology of Follicular lymphoma.
Irregular cleaved centrocytes and large centroblasts. Few to no TBMs. May or may not see follicular aggregates.
Describe the cytology of marginal zone lymphoma.
Polymorphous population including monocytoid and lymphoplasmacytic cells. Nearly impossible to diagnose by FNA.
Describe the cytology of SLL.
Monomorphous small lymphocytes with soccer-ball chromatin, often smudge cells. May have prolymphocytes and paraimmunoblasts. Trisomy 12 looks wrinkled/atypical.
Describe the cytology of Mantle cell lymphoma.
Monomorphous small to intermediate cells with fine chromatin. No blasts. “Pink” eosinophilic histiocytes? Rarely can look blastoid.
What is a good rule of thumb for distinguishing small and large cells?
Large cells should have nuclei larger than histiocyte nuclei (but may still be smaller than most epithelial nuclei).
Describe the cytology of DLBCL.
Large cells with large nucleoli and lymphoglandular bodies. Few lymphoid aggregates. May have predominant immunoblasts or centroblasts.
Name 3-5 subtypes of DLBCL and recall their cytology.
PMBL: Often limited sample due to compartmentalizing fibrosis.
Double-hit: Looks morphologically identical.
THRLBCL: Scarce tumor cells, hard to call.
PEL, Intravascular LBCL.
Describe the cytology of Burkitt lymphoma.
Intermediate-sized cells with round nucleoli, scant vacuolated blue cytoplasm, many apoptoses/mitoses and TBMs.
Describe the cytology of Plasmablastic lymphoma. Where is it generally found?
Predominant immunoblasts; isolated from oral cavity or other mucosal sites of the immunocompromised.
Describe the cytology of PTCL-NOS.
Non-specific; monomorphous small to large lymphocytes with irregular nuclei.
Describe the cytology of ALCL.
Intermediate and large cells including hallmark cells (horseshoe, donut, embryoid).
By what pattern does ALCL involve lymph nodes? What is the defining molecular change?
Involves LNs in a sinusoidal pattern.
ALK+ cases generally harbor a t(2;5) ALK-NPM fusion.
Describe the cytology of MF.
Cerebriform nuclei–but morphology is insufficient for diagnosis. Need immunophenotyping.
Describe the cytology of ATLL
Circulating “floret” cell nuclei with deeply basophilic and vacuolated cytoplasm.
Describe the cytology of LBL.
Highly cellular with monotonous lymphoblasts (2x normal size), increased mitoses, scant vacuolated cytoplasm. Hand-mirror?
Recall the spectrum of morphologies in PTLD.
May range from “polymorphic” (early) to “monomorphic” (late, looks like DLBCL).
What lymphoma is known to resemble carcinoma? Why?
ALCL; lack of lymphoglandular bodies, high cell clustering, rare spindling. Can also be EMA+ and drop many lymphoid markers.
What should be kept in the differential for LBL and Burkitt lymphomas?
Other SRBCTs (eg rhabdomyosarcoma, Ewing’s, neuroblastoma).
Recall the rare histiocytic and dendritic cell neoplasms and the stains that define them.
Histiocytic sarcoma: CD68, CD163
FDCS: CD21, CD23, CD35
LCH: CD1a, Langerin/CD207
What challenges do cystically degenerative SQC metastases pose?
They may be necrotic and be mistaken for branchial cleft cysts or EICs.
How does nasopharyngeal carcinoma usually present? Describe its cytology.
As an enlarged cervical node. Lymphocytes obscure clusters of malignant EBV+ epithelium.
What are the features of seminoma/germinoma?
Dispersed large vacuolated cells with macronucleoli on a tigroid background (proteinaceous fluid). Stains OCT3/4.
What sarcomas to tend to involve lymph nodes?
Synovial sarcoma, Kaposi’s sarcoma, FDCS, epithelioid sarcoma, rhabdomyosarcoma, angiosarcoma.
How can CHL and ALCL be distinguished?
Immunostaining for PAX5 and CD15. ALK can also help.
In general, how is clonality established in a T-cell proliferation?
Look for aberrant immunophenotype, perform PCR studies on TCR loci.
