Malignant peripheral nerve sheath tumors (MPNSTs) are sarcomas on peripheral nerves or nerve sheath. These MPNSTs can occur on any cell type and differs from one to other. A sarcoma is regarded as MPNST only when it is raised on the peripheral nerve or it exists on neurofibroma. MPNSTs usually present as an enlarging palpable mass. Pain is a variable complaint. Rapid enlargement occurs more often in the setting of NF1 and should raise concern for malignant degeneration of a neurofibroma.
In Spain identified 32 cases of cranial MPNST including our case. The age ranged from 5 to 75 years old with most patients being in the 5th and 6th decade. Male to female ratio is 2.5:1. Most cases are developed sporadically (50%), 31% arise from a malignant transformation of schwannoma and 19% from a neurofibroma. Imaging findings were not specific. The cranial nerve VIII is the most involved (15/32), followed by the Vth (10/32) and the VIIth (5/32). 4 cases had neurofibromatosis type 1 and 2 had neurofibromatosis type 2.