As reported, PIK3CA mutations occurred in 20–50% of breast cancers, especially including 35% of hormone receptor (HR)-positive breast cancers, 23% of human epidermal growth factor receptor 2 (HER2)-positive breast cancers and less than 10% in triple-negative breast cancer (TNBC) [234]. The gene discussed is ERBB2; the disease is triple-negative breast carcinoma.