Clonal heterogeneity by fluorescence in situ hybridization in multiple myeloma: enhanced cytogenetic risk stratification.

Background: Multiple myeloma (MM) is a proliferation of monoclonal plasma cells that accumulate in bone marrow, leading to bone destruction and marrow failure. Cytogenetic analysis is a challenge in MM because of the low mitotic activity and the rapid loss of plasma cells viability in bone marrow culture. Adding mitogens such as interleukin 6 (IL6) is known to promote the in vitro growth of myeloma cell lines and enhance the fluorescence in situ hybridization application. This study aims to evaluate the prognostic impact of cytogenetic abnormalities detected by enhanced interphase fluorescence in situ hybridization (iFISH) technique in Egyptian MM patients. Results: Patients who had hyperdiploidy significantly presented with higher Hb level and lower calcium levels compared to non-hyperdiploid patients. They were staged as stage I and II by International staging system (ISS) and considered as standard risk showing better response to treatment. On the contrary, features associated with a worse outcome were patients having del 17p and those belonged to intermediate and high risk groups. Conclusion: In conclusion, adding interleukin 6 to MM cell culture promotes the in vitro growth of myeloma cells and enhances the successful application of FISH technique. A comprehensive FISH probe set investigating high, intermediate and low-risk cytogenetic abnormalities is needed for accurate risk stratification. Hyperdiploid-myeloma is a favorable risk genetic subtype of MM associated with rapid response to therapy compared to patients having del 17p, t(4;14), and other 14q rearrangements rather than t(11;14) and t(6;14).