Malignant peripheral nerve sheath tumors of cranial nerves and intracranial contents: A clinicopathologic study of 17 cases

Malignant peripheral nerve sheath tumors (MPNSTs) arising from cranial nerves or their branches are very uncommon. The literature consists mainly of isolated case reports and small series. We identified 17 such cases in 14 males and 3 females. With one exception, the tumors affected adults (age range 5 to 69 y, mean 39, median 32). Sites of involvement included vestibular nerves (n=6), vagal nerves (n=4), facial nerves (n=3) (1 centered in the geniculate ganglion), and 2 unspecified cranial nerves in the posterior fossa. In addition, 1 tumor involved the optic chiasm (n=1). Only 1 tumor arose in brain parenchyma of (frontal lobe). All but 3 lesions were intracranial. Five tumors arose in patients who satisfied clinical criteria for neurofibromatosis type 1 (NF1). One patient with a vestibular tumor and presumed NF2 had previously undergone resection of a contralateral vestibular cellular schwannoma. One posterior fossa tumor was a malignant melanotic schwannoma. Four patients had postirradiation malignant peripheral nerve sheath tumors, 2 having been treated for optic chiasm glioma, both being NF1 affected. One patient was irradiated for hypothalamic pilocytic astrocytoma and another for cervical Hodgkin disease. Identifiable precursor lesions included schwannoma (n=4), plexiform neurofibroma (n=2), and solitary intraneural neurofibroma (n=2). All tumors were histologically high grade (6 grade III and 10 grade IV). Three tumors showed heterologous elements, 2 osseous, and 1 rhabdomyoblastic. More often scattered than diffuse, S-100 protein staining was noted in 11 of 16 tumors and variable collagen IV staining in 10 of the 16. Immunoreactivity for p53 protein was diffuse and strong in 7 of 11 tumors. Twelve patients died within 17 months to 3 years of diagnosis, 1 was lost to follow-up, 2 are very recent cases, and 2 patients are currently alive, 1 after 2 recurrences, and another with spinal leptomeningeal metastases. Malignant cranial nerve sheath tumors are rare and are associated with the same poor prognosis as those of spinal nerves at other sites.