HER2/CEP17 FISH Ratio Assay

**Semantic type:** Laboratory Procedure

**Definition:** A dual-probe fluorescent in situ hybridization-based assay used to determine the ratio of signal intensity present in a sample for two probes, one that is specific for ERBB2 (HER2) expression and one that is specific for chromosome 17 centromeric sequences (CEP17). Since the HER2 gene is present on chromosome 17, ratios greater than 1 indicate gene amplification or mRNA overexpression for HER2.

**Synonyms:** - ERBB2 gene copy number/Chromosome 17 copy number in Tissue by FISH - ERBB2/CEP17 FISH Ratio Assay - HER2/CEP17 Dual-Probe Fluorescence In Situ Hybridization Ratio Assay - HER2/CEP17 Fluorescence In Situ Hybridization Ratio Assay - HER2/CEP17 Ratio - HER2/CEP17 Ratio Assay - HER2/CEP17 Ratio Measurement