Hyperhaploid plasma cell myeloma

Conventional cytogenetics shows chromosome abnormalities in one third of plasma cell myeloma (PCM) cases. These chromosome abnormalities can be used to divide PCM into two major aneuploidy groups: hyperdiploid PCM and non-hyperdiploid PCM. Hypodiploid PCM is associated with a poor prognosis relative to other ploidy groups. Hypodiploid karyotypes usually have a modal number of 40 or more. Near haploidy is a rare phenomenon in PCM. We present three cases of PCM with hyperhaploid karyotypes from our laboratory, and review three cases reported in the literature. All six cases had modal numbers ranging from 27 to 33. Two copies of chromosomes 3, 7, 9, 11, 15, 18 and 19 were present in all cases. Five of the six cases had two copies of chromosome 21 and four of the six cases had two copies of chromosome 5. The three patients studied at our laboratory had aggressive disease and a short survival but the small number of cases makes predicting outcome in this group difficult. The consistent pattern of cytogenetic abnormalities present in these cases suggests that hyperhaploidy may be a distinct cytogenetic entity in PCM.