Woodruff, James M.

Malignant nerve sheath tumors involving cranial nerves are rare. We identified 13 cases of MCNST arising in cranial nerve or from benign nerve sheath tumors, all but three being intracranial. The patients included 10 males and 3 females, one pediatric (5 years) and the remainder ranging in age from 23 to 69 years (mean, 40). The vestibular (n=5) and vagal nerves (n=3) were favored sites, followed by posterior fossa (n=2), facial nerve (n=1), frontal lobe parenchyma (n=1) and the lateral ventricle (n=1). Some patients were known to have NF1(n=3) or probable NF2 (n=1). Three tumors arose in transition from a conventional schwannoma and one from a plexiform neurofibroma. The majority of the tumors (n=11) were high grade (5 WHO III and 6 WHO IV) lesions. Immunohistochemistry was performed in 11 cases; S‐100 protein reactivity was diffuse (n=1), partial (n=2), focal (n=5) or negative (n=3). Collagen IV was also diffuse (n=2), partial (n=3), focal (n=5) or negative (n=1). p53 protein staining was high (n=7), moderate (n=2), or low (n=2). Clinical follow‐up was available in 10 cases; of the 8 patients who died, six patients did so within six months of surgery, and two within three years. Only one tumor, a grade IV MCNST with heterologous bone formation, developed extensive spinal leptomeningeal drop metastases. The one pediatric patient is alive at 8 years. No clinically apparent systemic metastases were encountered.