PTEN and Cowden syndrome 1: CS is characterized by multiple hamartomas and carries a high risk of both benign and malignant tumors of the breast, thyroid, endometrium, colorectum, and kidneys.1) The most common malignancy associated with PHTS is breast cancer, with a reported lifetime risk of 85%.2) Here, we report a case of breast cancer with a novel mutation in the PTEN gene.