ERBB2 and endometrial serous adenocarcinoma: This study aimed to investigate human epidermal growth factor receptor 2 (HER2) protein expression and gene amplification status in uterine serous carcinoma (USC) and ovarian high-grade serous carcinoma (HGSC), determine the frequencies of HER2 overexpression/amplification and HER2-low expression, evaluate two current HER2 interpretation criteria, and analyze the relationship between HER2 status and patient prognosis.