Extracardiac rhabdomyoma: a rare entity.

Extracardiac rhabdomyomas are rare benign lesions of striated muscle origin. A review of the world literature revealed about 27 acceptable cases of benign, adult-type rhabdomyoma with a distinct male predominance. In most of the reported cases, the tumor was located in the head and neck region, usually submucosal or deeper. The case reported here is unusual because the tumor was subcutaneously located in the neck. The tumor was fairly well circumscribed, multilobulated, and easily shelled out. Light microscopy showed large round to elongated cells with granular, highly eosinophilic cytoplasm, often with peripheral vacuolation. Cross striations were infrequent. The nuclei were often peripheral and had prominent nucleoli. Electron microscopic studies confirmed the tumor's myogenic origin. Myofibrils with Z band material, abundant mitochondria, and glycogen particles were observed.