As with mutations that have a regulatory effect on the function of PTEN, mutations of PTEN is also a leading cause of cancer, with an estimated 50%–80% of sporadic tumors (includes endometrial carcinoma, glioblastoma and prostate cancer) and at 30%–50% in breast, colon, and lung tumors having monoallelic mutations of PTEN in common [1,109,168,169]. The gene discussed is PTEN; the disease is endometrial carcinoma.