As HER2 positivity was recommended to be defined as 2+ and 3+ scores on protein expression for gynecologic carcinosarcomas, only two patients (two of 11, 18.2%) met the criteria, which is significantly lower than what was reported in UCS while remarkably higher than that in serous ovarian carcinoma (9). This evidence concerns the gene ERBB2 and ovarian serous carcinoma.