QUANTIFYING CHROMOSOME CHANGES AND LINEAGE INVOLVEMENT IN MYELODYSPLASTIC SYNDROME (MDS) USING FLUORESCENT IN-SITU HYBRIDIZATION (FISH)

A simplified technique for fluorescent In situ hybridization (FISH) wa s used to investigate the prevalence of chromosomally abnormal clones in 13 cases of myelodysplastic syndrome (MDS). Biotinylated centromeri c probes for chromosomes 7, 8, 12 and X, as well as painting probes fo r chromosomes 7 and 11, were applied to air-dried bone marrow smears s tored from 6 to 23 months. Nine of the cases had been previously karyo typed, and five of these demonstrated normal karyotypes which were con firmed by FISH. The remaining four cases showed different chromosome c hanges. One case of sideroblastic anemia with chronic lymphocytic leuk emia showed minor clones with either monosomy 12 (12% of cells) or tet raploidy (15% of cells) by FISH, whereas metaphase cytogenetics had de monstrated trisomy 12 in 20% of cells, with no evidence of tetraploidy . Another case which had been previously karyotyped was found to have a t(7;11) in 90% of cells while only 10% of cells were shown by FISH t o contain this translocation. Monosomy 7 was demonstrated by FISH in a case of refractory anemia (RA), while trisomy 8 was found in a case o f RA with excess blasts in transformation (RAEB-T), and in both of the se cases the aneuploid clone was present in eosinophils as well as in erythroid and granulocytic precursors but not in lymphocytes or histio cytes, thereby demonstrating the value of FISH for identifying the aff ected cell lineage.