OBJECTIVE: To explore the value of multiplex fluorescence in situ hybridization 
(M-FISH) technique in the detection of the complex chromosomal aberrations 
(CCAs) in myelodysplastic syndromes (MDS).
METHODS: M-FISH was used in ten MDS patients with R-banding CCAs to refine the 
complex chromosomal rearrangements, the constitute of marker chromosomes, and to 
identify the cryptic translocations.
RESULTS: Thirty-seven kinds of structural rearrangements were detected by M-FISH 
including insertion, deletion, translocation and derivative chromosomes, among 
which 34 kinds were unbalanced rearrangements, and 3 were balanced 
rearrangements including t(6;22) (q21; q12), t(9; 19) (q13; p13) and t(3;5) (?; 
?). Seven abnormalities in the present paper were first reported in the 
literature. In addition, chromosome 17 aberrations (7/10) and -5/5q - (7/10) 
were the two most frequent abnormalities.
CONCLUSIONS: M-FISH could refine CCAs in MDS patients, find or correct the 
missed or misidentified abnormalities analysed by conventional cytogenetics.