A novel category stated by TCGA is the ultramutated POLE subgroup, which consists of 7% of ECs with unusually high mutation rates (232 × 10−6 mutations/Mb), generating extremely frequent mutations in cancer-associated genes such as PTEN (94%), PIK3CA (71%), PIK3R1 (65%), FBXW7 (82%), ARID1A (75%), KRAS (53%), and AIRD1B (47%) [10]. Here, PIK3CA is linked to cancer.