PIK3CA and ovarian clear cell cancer: In EOC, early genomic investigations demonstrated frequencies of genetic alterations for PIK3CA of 4%-12% (somatic mutations) in epithelial ovarian tumors[39,53,54], 20%-46% of clear cell ovarian cancers[53,55], 20% of endometrioid ovarian cancers, and 2.3%-3% of HGSOC[53,56].