Distinct Clinicopathological Features of HER2-Negative, HER2-Low, and HER2-Overexpressing Urothelial Carcinoma in a Large Chinese Cohort.

PURPOSE: To investigate the expression patterns of Human Epidermal Growth Factor Receptor 2 (HER2) and their clinicopathological associations across the full spectrum (negative, low, and overexpression) in a large cohort of Chinese urothelial carcinoma (UC) patients. MATERIALS AND METHODS: A multicenter registry study (April 2023-March 2024) across eight Chinese tertiary hospitals included 1054 UC patients. Demographic, clinical, and pathological data were analyzed to identify factors associated with different HER2 expression levels (IHC 0 vs. 1+ vs. 2+/3+). A subset of patients was evaluated for additional IHC markers (e.g., CK20, GATA3, P16, Uroplakin3, Ki-67). RESULTS: Of 1054 patients, 18.6% were HER2-negative (IHC 0), 23.0% were HER2-low (IHC 1+), and 58.4% exhibited HER2 overexpression (IHC 2+/3+). Increasing HER2 expression was significantly associated with bladder tumor location (63.1% in IHC 2+/3+, p < 0.001), infiltrative tumors (61.1% in IHC 2+/3+, p < 0.001), and high-grade tumors (62.5% in IHC 2+/3+, p < 0.001). In a sub-analysis comparing HER2-low (1+) and HER2-overexpressing (2+/3+) groups, multivariable logistic regression confirmed bladder primary site (OR = 1.783, p = 0.001), infiltrative status (OR = 1.492, p = 0.027), and high-grade differentiation (OR = 1.918, p = 0.001) as independent predictors of HER2 overexpression, though the model's predictive ability was modest (AUC = 0.64). Expression of CK20, GATA3, P16, and Uroplakin3 also differed significantly between HER2-negative and HER2-positive groups. CONCLUSIONS: This study delineates distinct clinicopathological profiles for HER2-negative, HER2-low, and HER2-overexpressing UC in Chinese patients. These findings provide a crucial evidence base for refining personalized treatment strategies, particularly for HER2-targeted therapies like antibody-drug conjugates (ADCs), across the entire spectrum of HER2 expression.