A forensic autopsy case: Sudden unexpected death due to cardiac inflammatory myofibroblastic tumor

•Autopsy case of sudden death due to cardiac inflammatory myofibroblastic tumor (IMT).•Cardiac IMT caused left ventricular outflow tract obstruction.•Sudden death due to cardiac IMT that is not related to acute coronary syndrome.•Cardiac IMT can be detected by postmortem computed tomography (PMCT). We report an autopsy case of a 25-year-old man with no medical history who died suddenly in an Internet cafe. He was found in cardiorespiratory arrest and did not respond to cardiopulmonary resuscitation. Traumatic lesions were not observed on his body. An autopsy was performed to investigate the cause of death. Upon examination, we discovered a heart tumor that infiltrated from the outside wall to the outflow tract of the left ventricle. Left ventricular outflow tract obstruction due to a cardiac tumor was considered the mechanism of death. Histological examination identified an inflammatory myofibroblastic tumor (IMT). The final diagnosis was death secondary to circulatory failure due to a cardiac IMT. Additionally, a cardiac tumor was diagnosed using post-mortem computed tomography. Only few cases of sudden unexpected death due to cardiac IMT have been reported; we report this case along with a review of the literature.