Although most fatal lung tumors are well diagnosed before a patient's death, occasionally forensic pathologists encounter cases of sudden death in which the presence of a primary small cell lung carcinoma was not suspected. We present the case of a 49-year-old man asymptomatic until 2 days before his death. The autopsy revealed a huge tumorous mass originating from the central bronchus, infiltrating the large vessels, pulmonary parenchyma, pericardium, and the right ventricle of the heart. Pericardial sac was distended due to pericardial effusion (700 mL). Examination also revealed metastases to the liver, pancreas, and right adrenal gland. Microscopic examination identified the primary neoplasm as a small cell lung carcinoma after common stain of hematoxylin-eosin, and additional immunohistochemistry were performed.