Frequent gains of the short arm of chromosome 9 in multiple myeloma with normal G-banded karyotype detected by comparative genomic hybridization

A number of genetic abnormalities have been detected in multiple myeloma (MM) using cytogenetic techniques. The prominent abnormalities are deletions of 13q an translocations affecting the IgH locus on 14q32. The recurrence of chromosomal abnormalities in MM suggests a specific role for them concerning its pathogenesis. We performed comparative genomic hybridization (CGH) on samples from 53 patients with MM and 4 with monoclonal gammopathies of undetermined significance. In 31 cases (54%), normal ratio profiles were found, whereas 26 cases (46%) had aberrant profiles. The most common aberrations were gains of 9p (n = 14), 11 (n = 9), and 21q (n = 5) and loss of 22 (n = 7). In earlier reports on cytogenetics of lymphomas, gains of 9p are described as characteristic of primary mediastinal B-cell lymphoma, but the consensus region is smaller than in the present study (9p23pter vs 9p13pter). Therefore, we suggest a stronger genetic affinity between MM and primary mediastinal B-cell lymphoma than between MM and other B-cell lymphomas. To support this suggestion, more molecular cytogenetic techniques and expression analyses have to be performed.