FISH
Also written as: FISH — fluorescence in situ hybridization
Fluorescence in situ hybridization, a laboratory technique used to detect HER2 gene amplification in breast cancer tissue samples.
Full Definition
Fluorescence in situ hybridization (FISH) is a molecular cytogenetic technique that uses fluorescent probes to detect specific DNA sequences within cells. In breast oncology, FISH is primarily employed to assess HER2 gene amplification when immunohistochemistry results are equivocal (2+ staining). The test determines the HER2/CEP17 ratio, with a ratio of 2.0 or greater indicating HER2 amplification. This information is crucial for determining eligibility for HER2-targeted therapies such as trastuzumab. FISH provides more precise quantification than immunohistochemistry and is considered the gold standard confirmatory test for HER2 status.
Usage
Usage note: Always capitalize as FISH when used as an acronym; lowercase when spelling out the full term.
In Context
- "FISH testing revealed HER2 amplification with a ratio of 2.4." — Laboratory report
- "Due to equivocal IHC results, FISH analysis was ordered to determine HER2 status definitively." — Clinical documentation