| Summary: | Follicular lymphoma (FL) and marginal zone lymphoma (MZL) are distinct clinicopathologic entities derived from small B-cells. Here we report an unusual case of simultaneous occurrence of CD10-negative, t(14;18)/BCL2-negative FL with rare residual germinal centers, and extranodal MZL with extensive amyloid deposition. Diagnostic challenges included a prominent nodular growth pattern and lack of expression of commonly used germinal center (GC) B-cell markers and the t(14;18)/BCL2 gene rearrangement characteristic of FL in an inguinal lymph node. The corresponding chest wall mass was diagnosed as MZL with extensive amyloid deposition. Though initially diagnosed as MZL involving a lymph node corresponding to the chest wall mass, newer markers of GC B-cells, HGAL and LMO2, as well as a newly described marker of marginal zone cells, MNDA, were helpful to establish the diagnosis of FL in the inguinal lymph node. Subsequent molecular clonality studies showed two distinct clonal B-cell processes in the two sites. This case illustrates the need for integration of morphologic findings with careful choice of ancillary diagnostic tests to establish definitive diagnoses among the spectrum of lymphomas derived from small B-cells.
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