RB1 and small cell lung carcinoma: Small cell lung cancer (SCLC) represents about 15% of primary lung cancers and is characterized by obligate bi-allelic mutations with a loss of RB1 and TP53. In contrast to non-small cell lung cancer (NSCLC), accounting for about 85% of lung cancer patients, targetable oncogenic drivers are uncommon in SCLC1,2.