PTEN and breast neoplasm: Mutations in PI3 kinase pathway are extremely common in tumors: for example, nearly 80% of cases of endometrial carcinoma (non-ultramutated samples) have inactivating mutations in PTEN (Cancer Genome Atlas Research Network et al., 2013) and 45% of human luminal A breast tumors harbor activating mutations in PIK3CA (Cancer Genome Atlas Network, 2012).