Primary plasma cell leukemia: Clinical, immunophenotypic, DNA ploidy, and cytogenetic characteristics

We report on a series of 26 patients diagnosed with primary (de novo) plasm a cell (PC) leukemia (PCL) in whom we analyzed the clinicobiologic characte ristics of the disease together with the immunophenotype, DNA cell content, proliferative index, and numeric chromosomal aberrations of the neoplastic PC, and compared them with 664 multiple myeloma (MM) patients at diagnosis . The median age, sex ratio, and bone lesion extension were similar, but PC L cases displayed a higher prevalence of clinical stage ill, extramedullary involvement, and Bence Jones cases, with fewer IgA cases than for MM patie nts. In addition, according to several prognostic indicators (beta(2)-micro globulin serum level, proportion of S-phase PCs, proteinuria, calcium serum level, lactate dehydrogenase [LDH] and renal function), the incidence of a dverse prognostic factors was significantly higher in PCL versus MM. Immuno phenotypic expression was similar for CD38, CD138, CD2, CD3, CD16, CD10, CD 13, and CD15, but PCL differed from MM in the expression of CD56, CD9 HLA-D R, CD117, and CD20 antigens. Twenty-two PCL cases were diploid and one was hypodiploid, while most MM cases (57%) showed DNA hyperdiploidy. With the f luorescent in situ hydridization (FISH) technique, 12 of 13 PCL cases displ ayed the numeric aberrations, -13 (86%), +/-1 (57%), +18 (43%), and -X in w omen (25%), but they lacked several numeric aberrations usually found in MM such as +3, +6, +9, +11, and +15. PCL cases had a lower overall response t o therapy than MM cases (38% v 63%, P = .01332). Among PCL patients, a tren d for a worse response was observed in cases treated with melphalan and pre dnisone (MP) versus polychemotherapy. Overall survival was significantly wo rse in PCL versus MM patients (8 v 36 months, P < .0001), but it was signif icantly better in PCL patients treated with polychemotherapy versus MP (18 v 3 months, P = .0137). By contrast, MM patients did not show significant d ifferences in overall survival according to the treatment used, MP or polyc hemotherapy. Ten variables seemed to predict survival in PCL patients, but only the beta(2)-microglobulin level and S-phase PCs retained an independen t value in multivariate analysis. In summary, our study illustrates that PC s from PCL display singular phenotypic, DNA cell content, and cytogenetic c haracteristics that lead to a different disease evolution versus MM. (C) 19 99 by The American Society of Hematology.