Perianal fetal rhabdomyoma: case report.

A 4-week-old female was referred with a firm, enlarging perianal mass present since birth. At surgery, the lesion appeared to be arising from the subcutaneous external sphincter. Local excision was successful with preservation of the external sphincter. Histologic examination showed a mixture of undifferentiated spindle cells as well as immature and maturing myofibers consistent with a fetal rhabdomyoma. This report represents the second case of a fetal rhabdomyoma arising in the perianal location. All pediatric cases of fetal rhabdomyoma in the literature are reviewed.