Sarcoma in neurofibromatosis 2: case report and review of the literature.

Neurofibromatosis type 2 (NF2) is associated with the development of several types of benign nervous system tumours, while malignancies are rare. We report a 22-year-old man who presented with retroperitoneal and spinal high-grade sarcomas with epithelial features. Samples showed a mixed epithelioid and spindled cell content with little associated matrix and inconclusive immunochemistry. Genetic analysis of a schwannoma and matched blood samples demonstrated a constitutional de novo substitution at the splice donor site of intron 8 of the NF2 gene and aa acquired large deletion of the entire NF2 gene as a second hit, with some loss of SMARCB1. The sarcoma also showed evidence of loss of SMARCB1 and NF2 with loss of INI1 staining. Unfortunately the mass was unresectable and the patient died 6 months after diagnosis. This malignancy was most consistent with SMARCB1-deficient epithelioid malignant peripheral nerve sheath tumour, although a significant differential was proximal-type epithelial sarcoma. Each differential has previously been reported only once with NF2. This demonstrates an extremely rare potential complication of the condition.