Fluorescence in situ hybridization to assess aneuploidy for chromosomes 7 and 8 in hematologic disorders

Stored, fixed cell suspensions of bone marrows from 70 patients karyotyped over a three-year period for myelodysplastic syndrome (MDS) or related hematologic conditions were retrospectively studied in two series using centromeric probes for chromosomes 7 and 8. Series I consisted of patient samples with numerical and/or structural abnormalities of chromosomes 7 or 8, matched with chromosomally normal samples from about the same time period. Series II consisted of consecutive MDS patient samples as well as patient samples in which one or more cells had numerical or structural abnormalities of 7 and 8. In both series, probes for chromosomes 7 and 8 were applied in each case and at least 100 nuclei were scored for each probe for the distribution of one, two, or three signals. Twenty-seven cases had clonal abnormalities by routine cytogenetics (RC): 12 with monosomy 7; one with monosomy 8; five with trisomy 8; nine with clonal abnormalities other than 7 or 8 aneuploidy. Eleven cytogenetically normal cases gave abnormal interphase FISH (IF) results; one was subsequently confirmed by metaphase FISH analysis to have a clonal structural abnormality of chromosome 7; one case with a trisomy 8 clone, in remission by RC, showed 35% of cells by IF with three signals for chromosome 8; one case had heteromorphic chromosomes by FISH. Of eight remaining cases, five (four with -7 and one with +8 by IF) were among 22 cases of cytogenetically normal MDS. Three remaining cases (two with +8 and one with both +7 and +8 by IF) had AML or MPD. The high rate of possible undetected monosomy 7, among MDS cases in particular, suggests all MDS cases should be screened by IF.