P21.13 Perineurial spread from a leiomyosarcoma of the infratemporal fossa

Abstract

Leiomyosarcomas are uncommon, malignant neoplasms of smooth muscle. They frequently develop in the gastrointestinal tract and myometrium, but account for only 1% of all head and neck sarcomas. Perineurial spread is a complication most commonly observed in tumors of skin and skin appendages. We describe a 47-year old woman with perineurial spread along the mandibular nerve from leiomyosarcoma of the infratemporal fossa. She presented with diplopia and headaches. Past medical history was remarkable for a right-sided parotid carcinoma treated with resection and external beam radiation 30 years prior. Neurologic examination revealed a partial sixth nerve palsy on the right side as well as decreased sensation and allodynia in the distribution of the mandibular and maxillary nerves. Magnetic resonance imaging showed an infratemporal mass lesion involving the ramus of the mandible and adjacent soft tissues. Faint enhancement was noted tracking along the mandibular nerve into the wall of the right cavernous sinus. Biopsy of the mass lesion was non-diagnostic. Mandibular nerve biopsy demonstrated perineurial spread from leiomyosarcoma. The case is unique based on its location, underlying tumor type, and pathogenesis. A comprehensive literature review did not reveal a similar case. Perineural spread is a challenging diagnosis. A tissue-based diagnosis is indispensable for proper management. Perineurial spread from a sarcoma should be considered in the differential diagnosis, especially when symptoms arise within a prior radiation field.