PIK3CA and ovarian serous carcinoma: The sequencing of a large number of ovarian tumor samples (n = 498) allowed further subtype classification, with a high prevalence of TP53 variants being identified in high-grade serous carcinoma (89.8% of cases), PIK3CA variants in ovarian endometrioid adenocarcinoma (49.0%) and KRAS variants in low-grade ovarian serous carcinoma (33.3%).