Primary splenic presentation of plasma cell dyscrasia: report of two cases.

Primary splenic presentation of plasma cell tumors is extremely rare. Recently we observed two female patients with primary (initially solitary) plasmacytoma of the spleen. While the pathoanatomical diagnosis of plasmacytoma could be established easily, the clinical picture in both cases was puzzling and allowed no definitive diagnosis to be made. One of the patients exhibited a long-standing monoclonal gammopathy. Repeated bone marrow examinations in both patients revealed slight increase in plasma cells (between 5 and 10% of all nucleated cells), but no infiltrates of multiple myeloma. The leading clinical feature in both cases was pronounced splenomegaly (780 g and 1600 g). Histologically both spleens exhibited marked infiltration by pleomorphic plasma cells, with monotypic expression of IgG kappa in one case and of the light chain lambda in the other. A broad panel of monoclonal antibodies detecting various hemopoietic and nonhemopoietic antigens was used to determine the immunophenotype of the neoplastic plasma cells, but in both cases they reacted only with a minority of the antibodies applied. The bone marrow in both cases remained free of tumorous infiltrates, but the disease progressed a few months after splenectomy with infiltration of the liver in one case and of lymph nodes in the other. To summarize, these two cases are definitely not multiple myelomas but could represent a distinct entity among the plasma cell dyscrasias for which the preliminary term "disseminated plasmacytoma with primary splenic presentation" is proposed.