PIK3CA and breast cancer: PIK3CA mutations were first identified in 2004 [7,8] and are now known to occur at high frequencies in a wide range of solid tumours, including breast cancer (31%), endometrial cancer (37%), cervical cancer (29%), bladder cancer (22%), anal cancer (27%), colorectal cancer (17%) and head and neck squamous cell carcinoma (14%) [7,8,9,10,11,12,13,14].