performed targeted next-generation sequencing testing on 45 LCNEC patients and classified LCNEC into two major types: SCLC-like (n=18; 40%), characterized byTP53+RB1 co-mutation/loss; NSCLC-like (n=25; 68%), characterized by the lack of coaltered TP53+RB1 (36). The gene discussed is RB1; the disease is small cell lung carcinoma.