PTEN and Cowden disease: The PTEN gene codes a dual-specificity phosphatase with lipid and protein phosphatase activity.77 Mutations in the PTEN gene cause Cowden syndrome, a rare autosomal dominant inherited disease that predisposes affected individuals to breast cancer, thyroid carcinoma, endometrial carcinoma, and hamartoma with high fat content.78 The risk of developing breast cancer before age 70 years is 30% to 50% in affected women, and most cases occur before menopause.