ERBB2 and breast cancer: HER2 positivity has been reported in bladder cancer (16%), esophageal cancer (14.9%), breast cancer (18.3%), gallbladder cancer (11.11%), cholangiocarcinoma (8.5%), gastric adenocarcinoma (17.3%), ovarian cancer of epithelial origin (8.16%), and various head and neck cancers (4–19%) [53].