Plasma cell DNA content in multiple myeloma and related paraproteinemic disorders. Relationship with clinical and cytokinetic features.

In 62 patients with multiple myeloma (MM) and related disorders, the nuclear DNA content distribution of bone marrow plasma cells was assessed by flow and conventional cytofluorometry. Abnormal distributions, suggesting the presence of aneuploid populations, were observed in 53% of MM at diagnosis, in 50% of benign monoclonal gammopathies and in 12% of Waldenström's macroglobulinemias. Eighty-six percent of aneuploid cases had DNA stem-lines falling between the diploid and triploid value. In advanced and relapsing MM, abnormal distributions were found in 75% of cases. In 4 out of 14 patients with MM serially studied during the course of disease, emergence of new abnormal clones was documented. The abnormal DNA content of bone marrow plasma cells was not correlated with any clinical and laboratory characteristic and it affected neither response to therapy nor survival in patients studied at diagnosis. In advanced phases of MM, the presence of abnormal clones was correlated with high plasma cell proliferation rates (studied by tritiated thymidine incorporation) and poor response to chemotherapy. Seven out of 8 patients in acute terminal phase of MM had abnormal clones. Among these, five had DNA stem-lines over triploid value.