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Cytogenetics in multiple myeloma (MM) cases are generally difficult to perform due to the low proliferation index of malignant plasma cells (PC) in most cases. Although IL-6 and GM-CSF stimulate the in vitro proliferation of malignant plasma cells, their usefulness for improving cytogenetic results in multiple myeloma patients remains questionable, because results which compare various culture conditions in a sufficient number of patients are not available. By using a miniaturized karyotypic method, we compared in 30 multiple myeloma patients the number and percentage of clonal abnormal mitoses obtained from 3 and 6 d bone marrow cultures performed without or with two combinations of cytokines: IL-6 + GM-CSF or IL-6 + GM-CSF + IL-2 + IL-4 + TNFalpha. The percentage of patients with an abnormal karyotype, which varied with the Durie and Salmon stage of the disease, as well as the type of numerical and structural karyotypic abnormalities that we detected, were in agreement with published results. The detection of clonal karyotypic abnormalities was better after 3d of culture without cytokine than in all other culture conditions. The higher percentage of patients at all stages of MM with an abnormal karyotype in our study (76.6%) than in previous ones (20% to 60%) is largely explained by the large number of mitoses analysed in six different culture conditions due to the use of a miniaturized karyotypic method.
Brigaudeau et al. (Sat,) studied this question.