CD274 and serous adenocarcinoma: Hamanishi et al [12] reported the proportion of PD-L1 high expression to be 68.6% in 70 cases of ovarian cancers, including 28 serous carcinomas, 22 clear cell carcinomas, 11 endometrioid carcinomas, 2 mucinous carcinomas, and 7 other types of ovarian cancer.