Long-term natural history of a neuromuscular choristoma of the sciatic nerve: a case report and literature review.

Neuromuscular choristomas are rare tumors with mature skeletal muscle elements admixed with neural elements. Follow-up results are limited, the natural history of neuromuscular choristomas is poorly understood. To date, 14 cases of sciatic nerve neuromuscular choristomas have been reported, but follow-up results were provided only for 10 cases (median duration: 2 years). The natural history of neuromuscular choristomas is therefore poorly understood due to lack of longitudinal data. We describe a case with long-term natural history for 17 years of the disease and provide a literature review of the reported cases. A 6 year old girl, with a 6 year history of left buttock mass with neonatal pathologic diagnosis of neuromusculoar choristoma, presented with intermittent left lower extremity weakness in July 2006. She had a left buttock mass for 6 years, and the neonatal pathologic diagnosis was neuromuscular choristoma. Magnetic resonance imaging (MRI) revealed fusiform enlargement of the left sciatic nerve with mild enhancement similar to that of the muscle. The pathology of a re-biopsy sample was also consistent with neuromuscular. choristoma. In follow up, the mass increased slightly, but MRI findings remained consistent, and her condition remained stable for 11 years after re-biopsy. Aggressive fibrosis known as complication by manipulation of neuromuscular choristoma was also not developed. The patient has been followed up for a total of 17 years and this is the only case of long-term natural history of neuromuscular choristoma.