EGFR and non-small cell lung carcinoma: Consequently, testing for EGFR mutations is currently standard practice only for stage IV or otherwise incurable NSCLC (3), which results in two distinct subpopulations of these patients: “de novo” cases that directly present with stage IV disease, and “secondary” metastatic EGFR+ NSCLC cases that are initially diagnosed with stage I-III disease and develop stage IV NSCLC through subsequent relapse or progression, upon which molecular analysis is performed and EGFR mutations are detected.