PIK3CA and breast cancer: We also found the considerable frequency of PIK3CA mutation all across BC subtypes, the luminal subtype (HR+/HER2−; 48.6%), HER2-enriched (39.5%), and triple-negative (57.6%) tumors in BCs overall with an average age of 49 years at diagnosis, which supported the apparently different biologic impact of PIK3CA mutation on specific cancer subtypes as previously described [11,33].