Loss of PTEN function via gene mutation, deletion or promoter methylation has been reported in a more selected subset of tumours, including endometrial cancer, glioblastoma, prostate, ovarian, thyroid carcinoma, and less frequently in hepatocellular carcinoma, breast, lung, renal cell carcinoma and melanoma. Inactivation of PTEN, as measured by immunohistochemistry, was found in about one-third (28%) of 236 breast cancer specimens