Schwannoma of the Posterior Tibial Nerve

Abstract

Background Schwannomas are rare, slow-growing, benign tumors consisting of Schwann cells. They may cause pressure along a bony structure, resulting in increased pain and discomfort. Less than 1% of schwannomas become malignant, and localization in the foot is uncommon (2%–3% of reported cases). Methods We present a case of a schwannoma of a branch of the posterior tibial nerve sheath. The goal is to assist in recognition, diagnosis, and treatment of schwannoma in the foot and ankle. This is a case of a 51-year-old male soccer player with a soft-tissue mass along the medial ankle at the tarsal tunnel area with an insidious onset (2 years). Physical examination revealed a 3.0 × 2.5-cm mass; magnetic resonance imaging confirmed location, size, and depth. Results Surgical resection of the soft-tissue mass was performed under general anesthesia. The mass was found to be superior to the flexor retinaculum and attached by a small nerve branch of the posterior tibial nerve that traveled through the flexor retinaculum. A tissue specimen was sent to the pathology laboratory, and a schwannoma was confirmed histologically. Conclusions Schwannomas can occur after trauma, especially if the posterior tibial nerve or its branches are affected intrinsically or extrinsically, leading to discomfort, pain, and numbness along the tarsal tunnel. Also, unique to this case, a schwannoma may occur along the small branches of the posterior tibial nerve and present anatomically superior to the flexor retinaculum.