[Plasma cell leukemia presenting with cleaved nuclei and a monocytoid appearance].

A 74-year-old man presented with anemia, thrombocytopenia and leukocytosis with 41% abnormal cells having cleaved and monocytoid nuclei. The bone marrow was infiltrated with 43.6% abnormal cells that were negative for peroxidase staining and positive for PAS staining. Surface antigen analysis revealed no expression of CDs 2, 3, 4, 8, 10, 19, 20, 13 or 33. Serum immunoelectrophoresis detected a monoclonal band, which was identifiable as kappa-type IgA protein. Immunostaining also revealed expression of IgA and kappa-type in the abnormal cells. The patient was diagnosed as having plasma cell leukemia but the morphological findings were unusual. Surface antigen analysis revealed expression of CD38 later. This case suggests that immunostaining of abnormal cells is required for the differential diagnosis of plasma cell leukemia in leukocytosis.