Oligosecretory Primary Plasma Cell Leukemia with Atypical Morphological Abnormality.

Plasma cell leukemia (PCL) is a rare variant of multiple myeloma. The detection of plasma cells in the peripheral blood and monoclonal protein in the serum or urine is important for the diagnosis of PCL. However, it is sometimes difficult to diagnose PCL in patients with atypical plasma cell morphology and/or those without detectable monoclonal protein. We herein report a case of oligosecretory PCL showing atypical morphology in leukemic cells with a convoluted nucleus and basophilic cytoplasm but without detectable monoclonal protein, except for serum free light chain. A flow cytometric analysis and pathological analysis were useful for the early diagnosis of PCL.