A malignant peripheral nerve sheath tumor (MPNST) arising from a schwannoma is extremely rare, with limited literature on its clinicopathologic features. Here, we present a case series and literature review on patients with MPNSTs arising from schwannomas. We performed a retrospective review of patients from our institution's records to identify those with MPNSTs arising from schwannomas. We conducted a search for additional cases from the literature utilizing PubMed. 20 patients (including 2 at our institution and 18 from 16 prior publications) were identified. The patients aged 22-93 (mean 52) years, and 63% were females. Histologically, while most MPNSTs arising from schwannomas were of epithelioid-type, 7 tumors (including 2 at our institution) were of conventional spindle-cell type. All 20 patients underwent surgical excision, while a subset received additional radiotherapy and/or chemotherapy. In 17 patients with available follow-up, the overall survival was 2-72 (median 12) months. MPNSTs rarely arise from schwannomas and should be considered in patients with a clinical diagnosis of schwannoma, however, with atypical radiologic or clinical features. MPNSTs arising from schwannomas can show epithelioid or spindle-cell histology and harbor an aggressive course, even with surgical excision and adjuvant treatment.
