Hyperhaploid plasma cell myeloma

Genetic Abnormalities in Multiple Myeloma: Prognostic and Therapeutic Implications

Some genetic abnormalities of multiple myeloma (MM) detected more than two decades ago remain major prognostic factors. In recent years, the introduction of cutting-edge genomic methodologies has enabled the extensive deciphering of genomic events in MM. Although none of the alterations newly discovered have significantly improved the stratification of the outcome of patients with MM, some of them, point mutations in particular, are promising targets for the development of personalized medicine. This review summarizes the main genetic abnormalities described in MM together with their prognostic impact, and the therapeutic approaches potentially aimed at abrogating the undesirable pathogenic effect of each alteration.

Poor overall survival in hyperhaploid multiple myeloma is defined by double-hit bi-allelic inactivation of TP53

Hyperhaploid multiple myeloma is a rare numerical aberration group defined by a range of 24-34 chromosomes, which is associated with a poor prognosis with a 5-year survival rate of 23%. Hyperhaploid patient samples (n=8) were sequenced and copy number and mutations identified. Samples had a median of 13 monosomies (range 12-14), which in general were those not associated with trisomies in hyperdiploid samples. The chromosomes traditionally trisomic in hyperdiploid myeloma were disomic in hyperhaploid myeloma with retention of heterodisomy. We examined the hyperhaploid samples for frequently mutated genes and found that 8/8 (100%) hyperhaploid samples had a mutation in TP53, exceeding the overall rate of mutation in newly diagnosed patients (5.5%), indicating an oncogenic dependency in this group. All samples with TP53 mutation also had monosomy of chromosome 17, indicating bi-allelic inactivation of TP53. As such, this high risk group is part of double-hit myeloma.

Hyperhaploidy is a novel high-risk cytogenetic subgroup in multiple myeloma

Hyperhaploid clones (24-34 chromosomes) were identified in 33 patients with multiple myeloma (MM), demonstrating a novel numerical cytogenetic subgroup. Strikingly, all hyperhaploid karyotypes were found to harbor monosomy 17p, the single most important risk stratification lesion in MM. A catastrophic loss of nearly a haploid set of chromosomes results in disomies of chromosomes 3, 5, 7, 9, 11, 15, 18, 19 and 21, the same basic set of odd-numbered chromosomes found in trisomy in hyperdiploid myeloma. All other autosomes are found in monosomy, resulting in additional clinically relevant monosomies of 1p, 6q, 13q and 16q. Hypotriploid subclones (58-68 chromosomes) were also identified in 11 of the 33 patients and represent a duplication of the hyperhaploid clone. Analysis of clones utilizing interphase fluorescence in situ hybridization (iFISH), metaphase FISH and spectral karyotyping identified either monosomy 17 or del17p in all patients. Amplification of 1q21 was identified in eight patients, demonstrating an additional high-risk marker. Importantly, our findings indicate that current iFISH strategies may be uninformative or ambiguous in the detection of these clones, suggesting this patient subgroup maybe underreported. Overall survival for patients with hyperhaploid clones was poor, with a 5-year survival rate of 23.1%. These findings identify a distinct numerical subgroup with cytogenetically defined high-risk disease.

Hyperhaploid uterine mesenchymal tumors-a novel genetic subgroup?

Hyperhaploid karyotypes have been described to occur in subsets of various solid tumors and leukemias. In these cases, monosomy is noted for most of the chromosomes while a few chromosomes still remain disomic. Evidence has emerged that at least in some tumor entities these remaining chromosomes are non-randomly selected. In addition, structural alterations can accompany the reduced chromosome number and secondary duplication of the chromosome complement is also a frequent finding. In this report, we describe hyperhaploidy in a case of an endometrial stromal nodule of a 50 year old woman who underwent hysterectomy because of symptomatic uterine fibroids. In addition, we review two other recently described cases of uterine mesenchymal tumors with that type of genetic alteration. Despite some histologic differences, striking similarities between these three cases exist with respect to the chromosomes were retained as disomic. Thus, the question arises if hyperhaploidy defines a novel genetic subgroup of uterine mesenchymal tumors.