[Plasma cell leukemia presenting with circulating villous lymphocytes and an indolent clinical course]

A 73-year-old man was admitted to our hospital in July 1996 because of lymphoctyosis and lumbago. Physical examination revealed hepatomegaly and anemia. Hematologic examination showed a hemoglobin concentration of 9.6 g/dl and a leukocyte count of 32,700/microliter with 74% abnormal mononuclear cells. In Wright-Giemsa stained blood films, these cells had short villi arising from 1 or 2 poles. Immunophenotyping of peripheral mononuclear cells showed moderate to strong expression of CD10, CD24, CD38, and sIg lambda, but not of CD19, CD20, or CD25. Southern blot analysis of the peripheral mononuclear cells demonstrated rearranged monoclonal bands in the C lambda. Urine immunoelectrophoresis detected a monoclonal band identifiable as lambda-type Bence Jones protein. In addition, bone X-ray studies disclosed multiple osteolytic lesions. A diagnosis of plasma cell leukemia was made, and the patient was placed on chemotherapy consisting of cyclophosphamide and prednisolone. No notable improvement in laboratory findings was seen but the patient experienced an indolent clinical course. He died of pneumonia in January 1998. The morphological and clinical findings were unusual for a case of plasma cell leukemia. This case study suggested that signs of lymphocytosis require immunophenotypic and electron microscopic studies for the differential diagnosis of plasma cell leukemia.