Schwannoma of Foot and Ankle: Seven Case Reports and Literature Review

Abstract

Background: Schwannoma is most often grown on the trunk, upper and lower extremities, and head and neck, but rarely on the foot. This study aimed to reveal clinical presentations, histopathology and treatment options for schwannoma of the foot. Materials and Methods: Seven schwannomas out of 174 soft-tissue tumors on the foot and ankle were retrieved from our Institute in a 3-year period, and 42 schwannomas on the foot and ankle in the literature in a 30-year period were reviewed. Results: The incidence of schwannoma of foot was found to be 4.0%. The patient age ranged from 8 to 84 years, with a mean of 47.4 years. More than 80% of tumors were located on the ankle, heel and plantar aspect. Overall, 77.6% of patients complained about a painful mass. Magnetic resonance imaging revealed a well-circumscribed, round or ovoid mass with iso-intensity signal compared with surrounding neuromuscular tissues on T1-weighted images and hyper-intensity signal on T2. Forty-eight out of 49 patients were treated with surgical excision or enucleation without recurrence in follow-up from 2 months to 4 years. Histologically, schwannoma was composed of hypercellular Antoni A zone with palisaded spindle cells with strong immunostaining for S-100 and hypocellular Antoni B zone with vascularization in myxoid stroma. Conclusion: Schwannoma of the foot and ankle is a rare, painful, indurated tumor. Magnetic resonance imaging reveals the location, size, texture and relationships with surrounding neuromuscular structures. Surgical excision is the primary treatment option with excellent outcome.Schwannoma, also called neurilemoma, derived from Schwann cells in the peripheral nerves, is a solid, slowgrowing tumor. It was first reported by Verocay in 1910 (1), and was named 'schwannoma' by Masson in 1932 (2). Schwannoma accounts for about 5% benign tumors as revealed by an analysis of 18,677 benign soft-tissue tumors by Kransdorf (3) and others (4). It frequently occurs in the trunk, flexor side of upper and lower extremities, head and neck (3, 5, 6), especially in the eighth cranial vestibular nerves (7-9), but is uncommon on the foot and ankle (10-12). Toepfer et al. observed 11 (10.5%) neurinomas, including both schwannoma and neurofibroma, out of 104 benign softtissue tumors of the foot and ankle at a university tumor institute between 1997 and 2015 (13). Kehoe et al. recorded 12 out of 104 (11.5%) peripheral nerve tumors on the foot in a 32-year period (7), and Carvajal et al. reported eight out of 87 (9.2%) schwannomas were located on the foot in a 16year period observation (14). In 1969, Das Gupta et al. analyzed 303 schwannomas with none of them being on the foot (5), whereas in 1998 with Chaudhuri, they reported four out of 104 schwannomas to be found on the foot (15). Odom et al. reviewed 557 schwannomas and noted 19 (2.93%) involving the foot (16). Most published results were reports of single case or small case series. Here, we report seven cases of schwannoma on the foot and ankle from our Institute in a 3-year period, and further...

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