Nodal marginal zone B-cell lymphoma resembling plasmacytoma arising from a plasma cell variant of localized Castleman's disease: a case report.

Nodal marginal zone B-cell lymphoma (NMZBL) occasionally represents prominent plasma cell differentiation. Recently, primary lymph node plasmacytoma has been suggested to represent an extremely plasmacytic differentiation of NMZBL. We here report a case of NMZBL showing histological features resembling plasmacytoma arising from a plasma cell variant of localized Castleman's disease (PCLCD). The patient was a 69-year-old Japanese female with a 20-year history of a right inguinal mass. Histologically, a prominent proliferation of plasma cells occupied the interfollicular area of the central portion of the lymph node, whereas centrocyte-like (CCL) cells were the main cellular component in the peripheral portion of the lymph node. Although most of the plasma cells were mature 'Marshalko-type', occasional atypical forms with enlarged nuclei were also present. The majority of the lymphoid follicles had atrophic or regressive germinal centers. A few lymphoid follicles were colonized by CCL cells. Immunohistochemistry study revealed that both plasma cells and some CCL cells had a monotypic intracytoplasmic lambda light chain. When monoclonal plasma cell infiltration is observed in PCLCD, the light chains are mostly restricted to the lambda chain. This case suggests that some plasma cell-containing tumors arising from PCLCD may represent a variant of NMZBL.