Although conventional cytogenetics is considered the gold standard to detect 
chromosomal abnormalities in myelodysplastic syndromes (MDS), fluorescence in 
situ hybridization (FISH) is being increasingly used additionally. However, the 
real contribution of FISH analysis in the cytogenetic diagnosis of MDS has not 
been well defined. The aim of this study was to evaluate whether FISH studies 
are able to reveal chromosomal abnormalities in MDS patients undetected by 
conventional cytogenetics. One hundred seventy-four FISH studies were performed 
on bone marrow samples of 60 patients with MDS. The number of FISH studies in 
each patient was variable (1-5). FISH studies confirmed the G-banding 
cytogenetic findings in 99.4% (153/154) of samples and detected cytogenetic 
abnormalities in 25% (5/20) of cases in which the conventional cytognetic study 
failed. These results indicate that FISH studies provide relevant information in 
MSD in which the conventional cytogenetic analysis was unsuccessful but add 
little value to a normal katyotype in conventional cytogenetic analysis.