HER2 (also known as ERBB2) amplification is detected in approximately 5% of all BTC cases, particularly in gallbladder carcinoma and in eCCA, where it is found between 15 and 20%.100,101 It is associated with worse OS.102 Several clinical phase II trials explored anti-HER2-targeted therapies in pretreated HER2-positive BTC patients that have shown clinical efficacy, including trastuzumab deruxtecan, trastuzumab + mFOLFOX, trastuzumab + pertuzumab, trastuzumab + tucatinib, and zanidatamab. This evidence concerns the gene ERBB2 and gallbladder carcinoma.