SIGNIFICANCE OF CIRCULATING PLASMA-CELLS IN MULTIPLE-MYELOMA

The number of circulating plasma cells (CPC) was determined on mononuc lear cell preparations after Giemsa (morphology) and light chain stain ing (immunocytochemistry). Both methods gave reproducible and identica l results when CPC were 1% or more. Using this limit, no CPC were obse rved in MGUS (0/11) and primary amyloidosis (0/2), whereas 45/98 (45.9 %) multiple myeloma (MM) pts had greater than or equal to 1% CPC. 3/14 pts (21.4%) in stage I, 5/13 pts (38.5%) in stage II, 20/28 pts (71.4 %) in stage III, 4/25 pts (16%) at plateau phase, and 13/18 pts (72.2% ) at relapse had greater than or equal to 1% CPC (p < 0.001). Mean bet a-2 microglobulin was 3.77 mg/l and 6.08 mg/l for pts without or with greater than or equal to 1% CPC, respectively (p = 0.0001). Presence o f CPC was also correlated with an higher percentage of bone marrow PC, but not with the number of Ki-67 positive BM-PC, and not with CRP or LDH levels. K/L and Gamma/Alpha CPC isotype ratio showed these cells a s monotypic in nearly all pts. The prognostic value could not really b e assessed in this study, as only the initial response to therapy was investigated, and the latter failed to give any difference between pts with and without CPC. So, presence of CPC is not an infrequent findin g, but is highly related to tumor mass and active disease; in most if not all patients they are monotypic and certainly belong to the malign ant clone. Their prognostic value is unclear but under current investi gation; CPC are correlated with B-2M level.