Multifocal adult rhabdomyoma of the neck: a rare entity

Extracardiac rhabdomyoma comprise 2% of all tumors of skeletal muscle differentiation. Seventy percent of extracardiac rhabdomyoma occur in the head and neck region and have been subclassified into adult and fetal types. There are only about 100 cases reported in the literature. A review of the world literature revealed about 19 acceptable cases of benign, multifocal adult-type rhabdomyoma with a distinct male predominance. The pathogenesis of this benign striated muscle tumor is still unclear. These slow-growing tumors remain asymptomatic for a long period. The diagnosis of head and neck rhabdomyoma is based on histology and immunhistochemical studies. The differential diagnoses of rhabdomyoma in adults are myoblastoma or Abrikossof tumor, reticulohistiocytoma, rhabdomyosarcoma and hibernoma. We present a case of multifocal rhabdomyomas in the paratracheal and parapharyngeal space and discuss the clinicopathological features of this lesion. Although adult rhabdomyomas have a distinct histology, they often are mistaken for a variety of other lesions, particularly Abrikossof tumor. Light microscopy showed large round to elongated cells with granular, highly eosinophilic cytoplasm, often with peripheral vacuolation. Histology showed typical patterns of an adult type of rhabdomyoma with focal cross-striations. Immunhistochemically, all applied muscular markers were positive. Electron microscopic studies confirmed the tumor's myogenic origin. Myofibrils with Z band material, abundant mitochondria and glycogen particles were observed. Treatment is usually complete excision. Local recurrences have been reported in some cases; malignant degeneration is not known.