SCLC-like LCNEC subset was characterized primarily by RB1 and TP53 inactivation, whereas NSCLC-like LCNEC subset was associated with KRAS, serine/threonine kinase 11 gene (STK11)/kelch-like ECH associated protein 1 gene (KEAP1) mutations alone or concurrently with TP53 mutations. The gene discussed is RB1; the disease is non-small cell lung carcinoma.