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Marginal Zone Lymphoma
Lessons From the Friday Unknowns
Histologic sections show fragments of fibroadipose tissue involved by an atypical lymphoid infiltrate focally arranged in nodules and sometimes separated by fibrous septa. The lymphoid cells are small, with mature chromatin and scant to moderate amounts of cytoplasm. Occasional large cells are seen, no apoptotic bodies and no necrosis present.
Immunohistochemical stains show that the atypical lymphoid cells are positive for CD20, CD79, PAX5, CD43 (dim) BCL2 (variable, dim), with a subset showing variable BCL6 expression and mostly negative for HGAL and LMO2. The cells are negative for CD3, CD5, CD10, CD15, CD21, CD30, CD43, cyclin D1, kappa and lambda light chain. The proliferation index measured by Ki-67 is approximately ~ 30% in the nodules. Pancytokeratin is negative.
Fluorescence in situ hybridization (FISH) studies are negative for rearrangements of BCL6, IGH, MALT1, t(11;14) or t(14;18).
The current findings are compatoble with a low grade B-cell lymphoma involving the fibroadipose tissue, most consistent with marginal zone lymphoma.
Link to digital slides: https://bit.ly/3WEWJIa | Case 4
