We used fluorescence DNA in situ hybridization (FISH) to detect chromosomal 
abnormalities as an indicator of minimal residual disease in follow-up samples 
from the bone marrow (BM), or peripheral blood, of 25 patients with leukemia, 
lymphoma and myelodysplastic syndromes. Trisomies were detected by interphase 
FISH with repeat-sequence probes (RSP) or by using metaphase FISH with 
whole-chromosome paint probes (WCP). Specific translocations were detected using 
WCP probes. Translocations were observed using metaphase FISH in two patients in 
uncertain or complete remission (CR), who both later suffered relapse. Five 
patients with no abnormal cells remained in CR. Four patients with trisomies 
detected during CR suffered relapse; metaphase FISH detected the trisomy in 
0.17-16% of metaphase cells. Five patients for whom the trisomy occurred in 
0.034% of cells remained in CR. Trisomic nuclei were observed in 0.27-2.3% of 
interphase cells, by means of RSPs, in four patients who later suffered relapse. 
Five patients with trisomic nuclei in 0.061% remained in CR. When two probes 
were used simultaneously in a sample from one patient, 1% of the residual cells 
were abnormal. The patient later suffered relapse. In one patient with 
anaplastic large cell lymphoma, CD30-positive interphase cells were shown to 
have trisomic chromosome 7 by immunophenotyping and FISH. Our results suggest 
that metaphase FISH using WCP probes is a sensitive and specific method for 
detecting minimal residual disease especially in patients with translocations.