Epidermal growth factor receptor (EGFR) is a tyrosine kinase that stimulates proliferation and differentiation by binding its ligand, epidermal growth factor (EGF). Dysregulation and mutations of EGFR have been documented in many solid tumor disease states such as head and neck, breast, renal, colon, glioblastoma multiforme, and non-small-cell lung cancer. Clinical diagnosis of EGFR upregulation or mutations is important in determining which tumors will respond to cancer therapy using tyrosine kinase inhibitors. EGFR upregulation is usually diagnosed by serologic testing and EFGR mutations by real-time PCR or next-generation sequencing.