Malignant peripheral nerve sheath tumor of intracranial nerve: a case series review

The incidence of malignant peripheral nerve sheath tumor (MPNST) is approximately 0.001%. Those involving intracranial nerves are even more exceptional. Little information is available concerning work up and management. Our objective is: (1) to review all cases of intracranial MPNST described in the literature, (2) to highlight the suspicion of intracranial MPNST, (3) to identify the gross pathology, the histopathology, the immunohistochemistry, (4) to discuss the differential diagnosis, the treatment, the recurrence rate, the follow-up, the incidence of metastasis and the prognosis.

We reviewed English, Spanish and French literature published from 1950 to date. We used the following Keywords: "malignant peripheral nerve sheath tumor", "cranial nerve", "neurosarcoma", "malignant schwannoma", "neurofibroma", "malignant neurofibroma" and "nerve tumor". We considered cases where MPNST involved an intracranial cranial nerve. The results yielded 20 relevant studies, in which 31 patient's records were transcribed. We also added our case to this series.

We 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. MPNST will strongly express protein S-100 and collagen IV-laminin. 13 cases were treated with radiotherapy for tumor recurrence and metastasis. In these cases the survival rate was better than the cases without radiotherapy. Fatal outcome occurred in 66% of patients whereas 19% were reported alive with or without complications. The seven cases reported to have metastasis were entirely to the spine. The mean time of recurrence or metastasis is 12.2 months.

MPNST of cranial nerves are very rare. In neurofibroma, even though MPNST is mainly associated to type 1, we should keep in mind its association to NF2. Mainstay of treatment is radical resection with adjuvant radiotherapy. Inaccessibility of cranial MPNST may explain the subtotal resection and thus the poor prognosis. Metastasis to the spinal cord is the most frequent one. A close postoperative follow-up is mandatory to eliminate recurrence.