Genital rhabdomyoma of the urethra in an infant girl.

Extracardiac rhabdomyomas are rare benign entities that usually occur in the head and neck region. Although genital rhabdomyoma is known to occur in the lower genital tract of young and middle-aged women, involvement of the anatomically adjacent urethra by rhabdomyoma is exceedingly rare. We present a case of genital rhabdomyoma arising from the urethra of an infant girl. The tumor was characterized by the submucosal presence of mature-appearing rhabdomyoblastic cells containing conspicuous cross-striations, with the cells set in a collagenous stroma. Necrosis and mitoses were absent. Skeletal muscle differentiation of the tumor cells was supported by positive immunohistochemical staining for desmin and myogenin. To our knowledge, this is the first case of urethral genital-type rhabdomyoma in a child.