We classified 13 endometrial cancer cell lines into 4 groups according to the mutational status of PIK3CA, PTEN, and K-Ras (Table 1): group A (n = 4), with coexistent mutations of PIK3CA and PTEN; group B (n = 5), with PTEN mutation alone; group C (n = 2), with coexistent mutations of K-Ras and PIK3CA; and group D (n = 2), with copy number gain of K-Ras (without any mutations in these 3 genes). This evidence concerns the gene PIK3CA and endometrial cancer.