The Art and Applications of Fluorescence In Situ Hybridization in Endocrine Pathology

Fluorescence in situ hybridization (FISH) or molecular cytogenetics is currently recognized as a reliable, sensitive, and reproducible technique for identifying the copy number and structure of chromosomes. FISH combines molecular genetics with classic cytogenetics and allows simultaneous morphologic evaluation on a single slide. Centromeric DNA probes are used to detect specific chromosomes and telomeric probes to demonstrate all chromosomes. Sequence-specific probes can localize in situ a single gene copy on a specific chromosome locus. FISH allows cytogenetic investigation of metaphase spreads and interphase nuclei. Several protocols have been proposed to analyze preparations from fresh samples or archival material. Comparative genomic hybridization (CGH) is a novel cytogenetic technique, which combines FISH with automatic digital image analysis. Comparative analysis of the hybridization products of tumor DNA and reference DNA with normal metaphase chromosomes, each labeled with color different fluorochrome, can retrieve chromosomal imbalances of the entire genome in a single experiment. FISH and CGH are powerful morphologic tools in understanding physiologic mechanisms and in resolving problems of the pathogenesis of several diseases. These techniques shed light on the cytogenetic background in many endocrinological disorders, providing a better understanding of the activities and alterations of endocrine cell function.