HER2 status detection methods are:

• A. IHC
• B. FISH
• C. IHC and FISH
• D. PCR and sequencing

Answer: (C)

The main idea is that determining HER2 status relies on two complementary approaches that look at different aspects of the gene: protein expression and gene copy number. Immunohistochemistry (IHC) assesses how much HER2 protein sits on the tumor cell membranes. A clearly positive result supports HER2-driven growth and eligibility for HER2-targeted therapy, while a clearly negative result argues against it. If the IHC result is equivocal, fluorescence in situ hybridization (FISH) is used to check whether the HER2 gene is amplified. Since protein overexpression and gene amplification don’t always coincide, using both tests provides the most accurate status to guide treatment decisions. PCR and sequencing are not standard for determining HER2 status because they detect DNA sequence changes rather than gene copy number, so they don’t reliably identify who will benefit from HER2-targeted therapies.