Cellular DNA content as a marker of human multiple myeloma

DNA flow cytometry of bone marrow cells from 61 patients with multiple myeloma in various stages of severity and treatment revealed a 65% incidence of aneuploidy. In the subgroup of 34 patients with plasmacytosis, 85% had aneuploid abnormalities. Of 50 patients with active disease, 76% had aneuploid bone marrow cells; conversely, 95% of patients with aneuploid abnormality had active multiple myeloma. The degree of ploidy abnormality was expressed as DNA index and ranged from 0.85 to 2.1. Except for one case of hypodiploidy in a patient with a previous history of malignant lymphoma, the remainder of patients showed hyperdiploid abnormalities with a modal DNA index value of 1.1. Thirty-eight of 40 patients with ploidy abnormality had unimodal DNA distributions; 2 patients had heteroploid abnormalities with 2 and 3 discrete subpopulations, respectively. Except for two patients, there was an excellent correlation between the percentage of cells with abnormal DNA content and the proportion of morphologically identifiable plasma cells (r = 0.91). Lack of ploidy abnormality in 15 patients with less than 10% bone marrow plasma cells may reflect a problem of recognition of small-degree aneuploidy rather than true absence, due to limits of resolution. The high incidence of DNA flow cytometncally detectable aneuploidy in patients with active disease makes DNA content a significant cellular marker of multiple myeloma.