Chromosomes in plasma-cell malignancies.

Much less is known about the chromosome changes in MM than in other hematological malignancies. The prevalence of abnormal karyotypes is unknown, but there is no evidence for malignant plasma cells or their precursors to have a normal karyotype. The chromosome changes found may be early events, but karyotypic evolution occurs early and rapidly. No specific structural or numerical chromosome anomaly is associated with multiple myeloma or plasma-cell leukemia. The changes found are those already known to occur in other B-cell malignancies, particularly B-CLL and diffuse small cell lymphoma. A 14Q + marker is present in about 30% of all karyotypically abnormal cases, and in 50% of the cases this is due to a t(11;14) (q13;q32). In a minority of cases deletions of 6q are found, and sporadically other B-cell translocations can be present. Karyotypes are often very complex with numerous structural anomalies involving mainly chromosomes 1, 11 and 17, and numerical anomalies involving chromosomes 3, 7, 9 and 11. Finally, the presence of structural or numerical anomalies of chromosomes 5 and 7 may be heralding or may be indicative of therapy-induced leukemia.