In fact, in a sizable percentage of lung cancer cases (10–14% cases), resistance to EGFR agents is linked to a lineage-switching phenomenon, which encompasses trans-formation of adenocarcinoma of the lung (LUAD) to squamous cell carcinoma (SCC) or small cell lung cancer (SCLC), correlating with additional mutations in p53 and Rb1. The gene discussed is TP53; the disease is small cell lung carcinoma.