Ancient Schwannoma: Case Report of an Unusual Entity in an Unusual Oral Location

Background: Schwannoma is an uncommon benign tumor that develops from Schwann cells in the peripheral nervous sys-tem; 25-50% of such tumors occur in the head and neck. A rare variety of schwannoma, known as an ancient schwannoma, exhibits calcification, cystic degeneration, hemorrhage, myxoid stroma, pleomorphism, and nu-clear hyperchromatism. Such characteristics may contribute to this tumor being incorrectly diagnosed as ma-lignant. Almost all reported intra-oral ancient schwannomas behave innocuously.Case Report: A 20-year-old man presented to the oral surgery clinic with a right facial swelling that began a few months be -fore. CT and MRI were performed and showed a well-defined cystic lesion anterior to the right masseter mus-cle, located in the subcutaneous area and measuring 28x24x20 mm. No extension to the surrounding tissues nor any other similar lesions were seen. Microscopic examination revealed an encapsulated nodular mass with cystic cavities, hemorrhage, and variably distributed myxoid and hyalinized stroma. The tumor demonstrated 2 distinct cell distributions: hypercellular areas (Antoni A) and myxoid hypocellular areas (Antoni B). Focal ar-eas in high-power magnification showed atypical cells with hyperchromatic and pleomorphic nuclei. The tumor cells showed diffuse positivity for S-100 in IHC. The diagnosis of ancient schwannoma was made. At 1-year fol-low-up, there was no evidence of nerve injury or recurrence.Conclusions: One more case of oral ancient schwannoma is added to the literature. This is the first reported in Saudi Arabia. It is prudent to be familiar with the degenerative and cytologic alterations of ancient schwannoma, as this may limit the likelihood of misdiagnosis and unnecessary treatment of this benign tumor, with an excellent prognosis.