Karyotype evolution of multiple myeloma.

To clarify the karyotype evolution of multiple myeloma (MM), multiple karyotypes of 22 patients with MM were analyzed using G-banding, and their karyotype evolutions were depicted as phylogenetic trees. Eleven patients exhibited highly complex karyotype evolutions, combining branched evolution, linear evolution, parallel evolution and macroevolution. While chromosomal structural abnormalities involving 14q32 were detected at the roots of the phylogenetic trees of karyotype evolution, aneuploidies and the other structural abnormalities were identified in both the initial clones and karyotypically evolved subclones. The findings indicated that aneuploidies might be caused by unequal chromosomal segregation, loss of the chromosome with unbalanced whole-arm translocation, and whole-chromosome doubling in patients with near-tetraploidy. Four patients had karyotype abnormalities (three del(20)(q) and one del(5)(q)) associated with myelodysplastic syndrome independent of the karyotype evolution of MM. In conclusion, the phylogenetic trees depicted by G-banding present the karyotype evolution of MM.