Primary marginal zone B-cell lymphoma of the lymph node resembling plasmacytoma arising from a plasma cell variant of Castleman's disease. A clinicopathological and immunohistochemical study of seven patients.

Nodal marginal zone B-cell lymphomas (NMZBL) occasionally represent prominent plasma cell differentiation. Recently, we presented a patient with NMZBL who exhibited histological features that resembled plasmacytoma arising from a localized plasma cell variant of Castleman's disease. To further clarify the clinicopathological, immunohistochemical, and genotypical findings, we studied seven such patients. Clinically, these patients were characterized by localized disease and an indolent clinical course with a slowly growing bulky mass in the affected lymph node. Only one patient exhibited paraproteinemia. Histologically, the lesions were characterized by numerous evenly distributed germinal centers in extensive sheets of plasma cells. Various numbers of centrocyte-like (CCL) cells arranged in a marginal zone distribution pattern occupied the peripheral region of the lymph node. The majority of the lymphoid follicles had atrophic or regressive germinal centers. A few lymphoid follicles were colonized by CCL cells. Immunohistochemistry showed that all of the lesions contained a monoclonal plasma cell population. In three tumors, a number of the CCL cells had a similar light chain restriction pattern to that observed in plasma cells. Two of the four patients evaluated exhibited clonal bands for the IgH gene by polymerase chain reaction assay. Moreover, the presence of surface IgM+, IgD- and CD27+ CCL- cells suggests that these tumors are derived from memory B-lymphocytes.