ERBB2 and breast cancer: Breast cancer is a highly heterogeneous tumor, exhibiting diversity in histological morphology and genomic differences, categorized based on histological morphology into non-invasive carcinoma, early invasive carcinoma, and invasive carcinoma, and further subtypes such as lobular carcinoma, ductal carcinoma, intraductal papillary carcinoma, papillary carcinoma, and medullary carcinoma; based on genomic differences, subtypes like Lumina A, Lumina B, HER2, triple-negative breast cancer (TNBC) are identified (4).