Rekhtman et al. conducted targeted sequencing for 45 pulmonary LCNEC cases, and genetically classified this neoplasm into three subgroups (SCLC characterized by TP53 and RB1 alterations, non-SCLC characterized by STK11 and KRAS alterations and well-differentiated neuroendocrine tumors characterized by MEN1 alterations) [26]. Here, RB1 is linked to large cell neuroendocrine carcinoma.