Cytogenetic abnormalities in a plasmacytoma.

By SEnclo MANCINELLI, JOHN R. DURANT, AND WILLIAM J. HAMMACK T SOMEWHAT CONSISTENT cytogenic changes in patients with multiple myeloma have recently been reported. Houston et al.,’ using phytohemagglutinin (PHA) stimulated peripheral blood cells, observed abnormal chromosomes in fifteen of twenty-four patients. The abnormal chromosomes were as large or larger than normal A group members with centromeric positions ranging from subtelocentric to submedian. These changes were usually but not invariably supernumerary and were present in a minority of cells examined. Because this abnormality was found in both myeloma and macroglobulinemia, Houston et al.1 termed this the MG ( monoclonal gammopathy) chromosome. Tassoni et al.2 studied the chromosomes in the bone marrow of fourteen patients with multiple myeloma. In five patients, they found, in a small percentage of cells, an acrocentric marker approximately the size of the long arms of the B group. This marker was also probably present in the bone marrow cells of two additional patients and was definitely present in the pleural fluid of a fifteenth patient whose effusion was proven to be due to myeloma. One patient had a few bone marrow cells with an abnormal chromosome similar in appearance to that reported by Houston et al.’ Numerous other nonspecific abnormalities have been noted, as recently reviewed by Das and Aikat.3 The significance of these markers is uncertain. The appearance of a marker in a small percentage of phytohemagglutinin sensitive circulating cells in a nonleukemic myeloma patient is surprising, especially in view of the usually normal marrow studies. It might be postulated that the abnormal cells were lymphocytic appearing circulating tumor cells or abnormal lymphoid precursors of myeloma cells. The general absence of the MG chromosome in marrow preparations could be due to dilution with more rapidly dividing normal myeloid elements, as suggested by Tassoni et al.2 to explain the low percentage of marker positive cells in their patients. Neither of these studies provided data indicating whether myeloma cells from marker positive patients usually, often, or rarely contained the abnormalities reported. The purpose of this report is to outline the cytogenetic abnormalities obtained from a patient with diffuse myelomatosis and a solid plasmacytoma. The studies performed on the tumor disclosed the presence of both types of