Trisomy 9 in a patient with secondary acute myelogenous leukemia detected by fluorescent in situ hybridization.

Fluorescent in situ hybridization (FISH) is a molecular cytogenetic technique that is playing an increasingly important role for augmenting the findings of conventional cytogenetics. Here we present the case history of a patient with the clinical diagnosis of secondary acute myelogenous leukemia whose bone marrow cells were found to be hyperdiploid with an extra C group chromosome in a less than optimal preparation. By using FISH the extra chromosome was unequivocally determined to be a chromosome 9. The detection of trisomy 9 in this patient underscores the utility of FISH as an adjunct to GTG banding in the routine diagnosis and management of leukemic patients.