Differentiating between congenital rhabdomyosarcoma versus fibromatosis of the pediatric tongue

Congenital rhabdomyosarcoma of the tongue is exceedingly rare. Fibromatosis of the tongue is also rare, and very difficult to distinguish from the spindle cell variant of rhabdomyosarcoma. Both appear histologically as spindle neoplasms replacing normal striated musculature of the tongue. The treatment protocol for the former has been developed by the Intergroup Rhabdomyosarcoma Studies (IRS) I-IV and requires surgery, radiation, and chemotherapy. For fibromatosis, complete surgical excision is usually adequate without additional therapy, although some cases of aggressive fibromatosis also require chemotherapy. With significant differences in appropriate treatment and prognosis, each entity must not be mistaken for the other. We review the differences in radiologic, histologic, and immunohistochemical (IHC) features of both entities.