HER2/ERBB2 In Solid Tumors: A Practical Guide To Testing And IHC Scoring
HER2 IHC scoring criteria are tumor‑specific and not interchangeable; inappropriate application can lead to patient misclassification.
HER2 (ERBB2) is a key biomarker in breast and gastric cancers and has recently gained tumor‑agnostic therapeutic relevance with FDA‑approved trastuzumab deruxtecan (T‑DXd) for any HER2‑positive (IHC 3+) solid tumour. This article reviews HER2 biology, testing modalities—including IHC, in‑situ hybridization, and next‑generation sequencing—and, critically, the tumor‑specific IHC scoring criteria needed for accurate classification across different tumour types. It highlights the central role of pathologists in assay interpretation, discusses gaps in organ‑specific scoring for many malignancies, and outlines future directions for standardization and validation of pan‑tumor HER2 assessment.
Accurate HER2 testing determines eligibility for emerging HER2‑targeted therapies such as T‑DXd across multiple solid tumours. Misapplication of breast‑centric scoring to other cancers can result in inappropriate treatment decisions, underscoring the need for tumour‑appropriate IHC criteria to optimise patient outcomes.
Evidence level: Korai humán adat. Kis vagy feltáró emberi adat.
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