Utility of multicolor fluorescent in situ hybridization in clinical cytogenetics

Purpose: Multicolor FISH (M-FISH) was introduced in 1996 to scan all 24 chr omosomes in different fluorescent colors by use of a specific filter set an d computer software. However, the clinical utility of M-FISH has been limit ed because of the lack of commercial availability of reagents and hardware. We have evaluated M-FISH for identification of markers, derivative chromos omes, and complex karyotypes. Methods: We present our findings based on a r epresentative sample of one normal and six abnormal cases from a variety of tissue types. The results of NI-FISH were confirmed by other well-establis hed FISH probes. Results: M-FISH analyses were successful in all six cases. The derivative chromosomes, ring, and a complex karyotype were resolved. C onclusions: We find M-FISH to be an invaluable tool for a high degree of ac curacy and efficiency for chromosome identification. The limitations simila r to spectral karyotyping system (SKY) include the inability to detect intr a chromosomal anomalies, abnormalities involving the p-arms of acrocentrics and areas rich in highly repetitive DNA. In addition, there are some conce rns of misinterpretation due to overlap of fluorophore combinations of diff erent chromosomes, especially for subtle insertional translocations.