The development of next-generation sequencing has led to the identification of more mutated genes in a series of early breast cancers, including tumor protein p53 (TP53) (41% of tumors), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) (30%), MYC (20%), phosphatase and tensin homolog (PTEN) (16%), cyclin D1 (CCND1) (16%), ERBB2 (13%), fibroblast growth factor receptor 1 (FGFR1) (11%), and GATA3 (10%) [18, 19]. The gene discussed is PTEN; the disease is breast cancer.