Working Diagnosis:
Left Sciatic Nerve Schwannoma

Treatment:
The patient was referred to Plastic Surgery for surgical excision of the mass. The patient underwent excision and biopsy of the sciatic nerve tumor with decompression of the sciatic nerve, complete release and myomectomy of the piriformis muscle. The pathology was consistent with a Schwannoma.

Outcome:
After successful removal of the Schwannoma, his symptoms resolved. The patient was able to return to daily activity without any residual pain.

Author's Comments:
Schwannomas are rare, most often well-encapsulated, benign peripheral nerve sheath tumors that grow from Schwann Cells. They can be divided histologically based on their characteristics. Fewer than 50,000 people in the United Stated have been diagnosed with a Schwannoma. They most commonly occur between the age of 20-50. The most common areas of occurrence include the head, neck, and extremities.

They can be associated with certain genetic disorders including Neurofibromatosis type 2, Schwannomatosis, and Carney Syndrome, but most often occur sporadically. They can arise from both motor and sensory nerves. Longstanding schwannomas, which used to be called ancient Schwannomas, can show different degenerative changes histologically. The most appropriate imaging modality is an MRI with and without contrast. Treatment is dependent on the size and current symptoms, ranging from watchful waiting to surgical excision. They rarely have malignant transformation. Surgical treatment complications include motor and sensory deficits. If surgically excised, they usually do not recur.

References:
Hirai, Toshihide, et al. Predictive Factors for Complications after Surgical Treatment for Schwannomas of the Extremities.; BMC Musculoskeletal Disorders, U.S. National Library of Medicine, 11 Apr. 2019, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6460649/.

NIH. Schwannoma - about the Disease.; Genetic and Rare Diseases Information Center, U.S. Department of Health and Human Services, https://rarediseases.info.nih.gov/diseases/4767/schwannoma.

Yonezawa, Hirotaka, et al. Structural Origin and Surgical Complications of Peripheral Schwannomas.; Anticancer Research, International Institute of Anticancer Research, 1 Nov. 2020, https://ar.iiarjournals.org/content/40/11/6563.

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