Benign triton tumor of the trigeminal nerve.

Benign triton tumor (neuromuscular hamartoma) is a rare tumor of the peripheral nerves, comprising mature neural and striated muscle elements. We report the third case, according to the literature, of a benign triton tumor affecting the Vth cranial nerve in a 4-year-old male child. The tumor was seen to involve the mandibular division of the trigeminal nerve in the infratemporal fossa and extend intracranially by eroding the base of middle cranial fossa. The mass was totally excised. In the tumor, bundles of axons intermingling with fascicles of relatively mature skeletal muscle were found. This type of hamartomatous lesions of neuroectodermal-mesenchymal origin could have arisen as the result of incorporation of mesenchymal tissue into nerve sheaths during embryogenesis or aberrant differentiation of neuroectodermal component into mesenchymal elements.