Genomic Evolution in Myelodysplastic Syndrome (MDS). C. Szych, R. Felgar, J. O'malley, J. DeFeo, M.A. Iqbal, N. Wang. Pathology, University of Rochester Medical Center, Rochester.
   To define the genomic aberrations associated with the genesis and progression of MDS, 366 cases with an indication of myelodysplastic syndrome were analyzed using G-banding. Chromosomal aberrations were detected in 101 cases. Of these, single genomic aberrations were detected in 66 cases; 9.09% with del(5q), 7.58% with del(20q), 7.58% with +21, 4.55% with -7, 4.55% with +8 and 28.79% with -Y. Multiple genomic aberrations were detected in 35 cases; 54.28% with del(5q)/-5, 34.28% with del(7q)/-7, 22.86% with del(20q)/-20, 22.86% with -18, 20.00% with -13, 17.14% with +8, 8.57% with +21 and 17.14% with -Y. The incidence of -5/5q- and -7/7q- is high in both cases with single aberrations and multiple aberrations. This suggests that these abnormalities are associated with genomic instability which leads to multiple chromosomal aberrations. In contrast, the aberrations of +8, +21, -13, del(20q) and -Y are more prominent in the cases with a single aberration than those in multiple aberrations, which suggests that these abnormalities are primary aberrations with less genomic instability toward chromosomal evolution. The aberration of -Y was identified only in cases over the age of 55 indicating that aging contributes a great deal to the loss of the Y chromosome. Statistical analysis is being conducted to verify the concordance and discordance of the various chromosomal aberrations identified in MDS.