Extracardiac rhabdomyoma: a clinicopathologic study and review of the literature.

Extracardiac rhabdomyomas are rare benign neoplasms that in the past have been divided by histologic criteria into adult and fetal types. In this series, 15 previously unpublished cases are presented and analyzed in combination with 51 acceptable cases from the literature. The adult type of rhabdomyoma occurs almost exclusively in the head and neck region (93% of all cases), particularly in the larynx and pharynx of adult males. The fetal type of rhabdomyoma may be subdivided on histologic grounds into myxoid and cellular variants. The fetal myxoid type usually occurs in the vulvovaginal region of middle aged women or in the postauricular region of male infants. The fetal cellular type has not been previously emphasized. This type tends to occur in the head and neck region of adult males. It may be mistaken for a sarcoma because of its high degree of cellularity. Local recurrence of a rhabdomyoma is rare and has only been occasionally reported in the adult type of rhabdomyoma. In no instance has a rhabdomyoma been shown to possess aggressive local growth or metastatic potential. Therefore, it is essential that these neoplasms be recognized histologically and that they be treated conservatively by local excision.