Detection of monosomy 7 and trisomies 8 and 11 in myelodysplastic disorders by interphase fluorescent in situ hybridization. Comparison with acute non-lymphocytic leukemias.

Cells from 50 patients with myelodysplastic syndrome (MDS) and 20 patients with acute non-lymphoblastic leukemia (ANLL) were studied by fluorescent in situ hybridization (FISH) using alphoid biotinylated probes to detect numerical chromosome 7, 8 and 11 aberrations in interphase nuclei. FISH data were compared with cytogenetic results. Both methods were in agreement in 25/50 MDS and 20/20 ANLL cases. Trisomy 11 was found neither by cytogenetic study nor by FISH. In 11 MDS patients the percentage of abnormal cells was higher by FISH than by classical cytogenetic analysis. FISH revealed monosomy 7 which was undetectable by karyotypic study in 5-22% cells from 15 MDS patients. It also allowed the identification of two small markers and a ring chromosome in two MDS cases. FISH hence appears to be useful for the detection of minor abnormal clones and is a convenient complement to conventional cytogenetic analysis in the study of MDS.