EGFR (HER1), epidermal growth factor receptor, is a tyrosine kinase receptor, which activates RAS/RAF/MEK and PI3K/AKT/mTOR pathways, leading to increased cell proliferation and growth. EGFR G721S lies within the protein kinase domain of the EGFR protein. G721S has been identified in the scientific literature in lung cancer, but has not been biochemically characterized and therefore, its effect on EGFR protein function is unknown. EGFR mutations are rare and in prostate adenocarcinoma and are identified in only about 1% of cases. The clinicopathologic significance of the EGFR G721S variant in prostate cancer remains to be fully elucidated.