Plasma cell leukemia: a report on 15 patients.

Plasma cell leukemia (PCL) can be considered the leukemic variant of multiple myeloma. The diagnosis is based on hematological features, including a plasmacytosis exceeding 2 x 10(9)/l and any evidence of a clonal plasma cell proliferation. There are two forms of PCL: the primary form occurring in individuals without preceding multiple myeloma, and the secondary form arising as a late manifestation in patients with multiple myeloma. From 1974 to 1988 we diagnosed 8 primary PCL cases out of a total 301 multiple myeloma cases (incidence, 2.6%) and a total of 847 acute leukemia cases (incidence, 0.9%). During the same period we observed in 7 multiple myeloma patients a terminal PCL, for an incidence of PCL in myeloma of 2.3%. Most clinical characteristics were similar in both types of plasma cell leukemia. In particular we found no difference in the average age and in the incidence of bone pain, hepatosplenomegaly, lytic bone lesions. None of our cases showed a clinically relevant lymphadenopathy either as presenting symptom or during the course of the disease. The values for hemoglobin, leukocytes, plasma cells, serum creatinine and calcium did not differ significantly between the two groups of patients. The median survival was 7 months for patients with primary PCL and 1 month for patients with secondary PCL. 5 of the 8 patients with primary PCL obtained a response to conventional myeloma therapy including single alkylating agents, with a duration ranging from 7 to 44 months. Only 1 of the patients with secondary PCL had a partial response after combination chemotherapy.