PIK3CA and endometrial endometrioid carcinoma: The most frequently altered gene in endometrioid endometrial carcinoma is PTEN (phosphatase and tensin homologue deleted from chromosome 10), also called MMAC1 (mutated in multiple advanced cancers 1). PTEN behaves as a tumor suppressor gene, is located on chromosome 10q23.3 and encodes a lipid phosphatase that antagonizes the PI3K/AKT pathway by dephosphorylating PIP3, the product of PI3K.