Primary plasmacytoma of lymph nodes.

Primary plasmacytoma of the lymph nodes is very rare, and there are fewer than 20 reported cases. These cases appeared to have a better prognosis than other extramedullary plasmacytomas, with rare recurrence and no progression to myeloma after treatment. To better characterize the clinicopathological features and the pathogenesis of primary plasmacytoma of the lymph nodes, we reviewed our consultation files and retrieved seven such cases. The age of presentation ranged from 39 to 76 years (median age, 59 years), with three women and four men. The clinical follow-up varied from 1 to 14 years. All patients presented with enlarged lymph nodes and had an indolent clinical course, except for one patient with slow progression and increasing numbers of bone marrow plasma cells. Five patients were treated with excision only and two with excision and chemotherapy. None of the patients had recurrence or developed multiple myeloma. All cases showed immunoglobulin light chain restriction, four with monotypic lambda and three with monotypic kappa. One patient had extensive nodal amyloid deposition. Four cases had monoclonal heavy chain expression, three with monoclonal immunoglobulin (Ig) G and one with monoclonal IgM. All cases were negative for CD20 and CD43, and six cases expressed CD79a. Overexpression of p53 and bcl-2 was not detected by immunostaining in any of the cases. Epstein-Barr viral (EBV) RNA was not detected in all seven cases by in situ hybridization, and no Kaposi's sarcoma-associated herpesvirus (KSHV) DNA sequences were detected by polymerase chain reaction in five cases. Our results confirm a more favorable outcome and rare progression to multiple myeloma in primary nodal plasmacytomas after excision or chemotherapy. The results of oncoprotein and viral studies suggest that the pathogenesis of primary nodal plasmacytoma may not be due to bcl-2- and p53-associated changes or viral-induced changes by EBV and KSHV.