HER2 gene amplification in breast cancer is tested by FISH (fluorescence in situ hybridization). What HER2/CEP17 ratio on FISH indicates gene amplification?

• A Ratio ≥1.0
• B Ratio ≥3.0
• C Ratio ≥4.0
• D Ratio ≥2.0 ✓

Explanation

Per ASCO/CAP guidelines, HER2 gene amplification by FISH is defined as a HER2/CEP17 signal ratio ≥2.0 or an average HER2 copy number ≥6.0 signals per cell (in the 2018 updated guidelines, multiple groups require additional IHC correlation). A ratio ≥2.0 indicates amplification and predicts response to trastuzumab (Herceptin). CEP17 is the chromosome 17 centromere control probe.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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