However, after further stratification, only one out of 13 OCS cases (7.7%) was found with positive HER2 expression, which is significantly lower than in uterine carcinosarcoma (UCS) (12/65,18.5%), and our study seemed to hold a pessimistic result of HER2 expression in OCS as, elaborated in the Discussion. This evidence concerns the gene ERBB2 and uterine carcinosarcoma.