Fluorescent in situ hybridization for assessing the proportion of cells with trisomy 4 in a patient with acute non-lymphoblastic leukemia

A case of acute non-lymphoblastic leukemia is described in which fluorescent in situ hybridization (FISH) helped to resolve initially conflicting conventional cytogenetic results. Identification and assessment of the proportion of cells exhibiting trisomy of chromosome 4 in the patient's bone marrow were made using a probe which hybridizes to the centromeric region of chromosome 4. These FISH results were consistent with our retrospective GTG-banded analysis but differed from another study conducted elsewhere. Factors such as culture conditions and duration of culture which may have influenced the proportion of leukemic to nonleukemic cells are discussed. Fluorescent in situ hybridization is a powerful adjunct to conventional cytogenetic analysis and may prove to be a useful tool for monitoring minimal residual disease in this patient.