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Fluorescence in situ Hybridization is one of today's most important diagnostic tools. It uses DNA probes comprised of specific nucleic acid sequences attached to fluorescent molecules. These probes can be used to determine the origin of marker chromosomes, to identify extra material in case of unbalanced translocations and to determine the presence of gene fusions.

Fluorescence in situ Hybridization Process

Fluorescence in situ Hybridization (FISH) for Detection of Genetic Alterations in Bladder Cancer Cells:
Bladder Cancer is the fifth most common type of cancer in the United States. Ninety percent of bladder cancer cases are transitional cell carcinomas (TCC). At presentation about 75% of tumors are superficial, of which 50% to 80% will have one or multiple recurrences, and 15% to 25% will progress to muscle-invasive tumors.

Follow-up cystoscopy and urine cytology have been used to detect recurrence and tumor progression in patients with superficial TCC. However, low-grade tumors tend to have false negative cytology results.

Several genetic alterations have been identified to occur at high frequency in bladder cancer. These include the loss of portion of chromosome 9 (presumably carrying a tumor suppressor gene), as well as numerical change in chromosomes 3, 7, and 17. Using a multicolor set of fluorescent DNA probes, several studies have demonstrated that detection of chromosomal abnormalities by fluorescence in situ hybridization (FISH) has a higher sensitivity in detection of TCC (transitional cell carcinoma) recurrence than does cytology, while maintaining high specificity. This technique has been validated for use as an adjunct to urinary cytology utilizing thin layer liquid-based preparations from routine urine specimens.

Random urine specimens are collected in a dedicated FISH urinary collection kit and forwarded to our laboratory. Upon receipt, a urinary cytology specimen is prepared for immediate evaluation and is examined by a cytopathologist for the presence of obvious neoplasia or findings of immediate import. This latter report is sent within 24 hours to the clinician as a preliminary “first” report. Separately, another sample of the same specimen is prepared as a separate thin layer of cells for FISH. These latter cells are then treated with special chemicals to expose the nuclear material in question and are then hybridized with the fluorochromes and fluorescent DNA probes in search for aneuploidy. The finding of aneuploidy (excess chromosomal mutations and abnormalities) by FISH is an indication that a physical abnormality is present in the urinary tract and requires further evaluation by a specialist.