LAUSR

BACKGROUND Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas, with approximately 50% occurring in patients diagnosed with neurofibromatosis type 1 (NF-1). NF-1 occurs in approximately 1/3000 individuals, and given that the lifetime prevalence of MPNST is estimated at 8%-13%, synchronous development of separate MPNSTs is plausible. We sought to report the incidence of synchronous MPNST in a cohort of pathology-proven cases since 1994. METHODS Records since 1994 were queried and identified 192 patients with pathology-proven MPNST. Medical records of these patients were reviewed to search for patients with synchronous MPNSTs. RESULTS Retrospective review of 192 patients treated for MPNST at our institution (including 71 patients with NF-1) revealed only 1 patient with synchronous MPNSTs. A 48-year-old woman with NF-1 presented with progressive right upper and lower extremity pain and radicular symptoms. Biopsies of right sciatic and median nerve lesions revealed high-grade MPNST, and she underwent radiotherapy and complete resection of both masses. Due to initial nonspecific biopsy results and patient preference, treatment of the median nerve lesion was delayed by 8 months. She did not have recurrence of her disease at the 18-month follow-up. CONCLUSIONS Synchronous development of MPNST is unusual, with an incidence of 1.4% in our cohort of NF-1 patients with MPNSTs. Given the reported incidence of synchronous MPNST, the rate of malignant transformation in NF-1 may be overestimated. However, heightened suspicion for malignant transformation should continue in patients harboring a diagnosis of MPNST.