Mediastinal rhabdomyoma: a case report and review of the literature.

An incidental anterior-superior mediastinal rhabdomyoma is reported in a 68-year-old man who died of hypovolemic shock as a result of massive blood loss due to transection of aorta after being hit by a moving motor vehicle. This is the third reported case of mediastinal rhabdomyoma in the literature. The immunohistochemical evidence of expression of muscle-specific markers supports the rhabdomyomatous nature of this neoplasm, and electron microscopic demonstration of haphazardly arranged myofilaments with prominent Z bands, "jack-straws" in the mitochondria, and the absence of desmosomes is supportive of extracardiac origin of this rhabdomyoma. The possible histogenesis of extracardiac adult rhabdomyoma (EAR) in the anterior-superior mediastinum from the thymic myoid cells is also discussed.