ERBB2 and breast cancer: Based on molecular features, breast cancer is mainly divided into four subtypes: Luminal type (60-70%): including Luminal A (HR+/HER2-/low Ki-67) and Luminal B (HR+/high Ki-67); HER2+ type (20%): driven by HER2 overexpression leading to aggressive growth; Triple-negative breast cancer (TNBC) (10-15%): ER/PR/HER2-negative, with a high risk of recurrence and metastasis (3, 4).