PIK3CA and breast cancer: Despite the pre-clinical evidence that PIK3CA is an oncogene, clinical studies of the outcomes of breast cancer patients with and without PIK3CA mutations have had conflicting results, demonstrating worse outcomes among patients with tumor PIK3CA mutations, no differences in outcomes by mutation status, and, most recently, better outcomes for women with hormone receptor positive (HR+) tumors with PIK3CA mutations [7, 9, 10].