Malignant epithelioid cranial nerve sheath tumor: case report of a radiation response.

Malignant epithelioid nerve sheath tumors (MESs) especially those involving intracranial cranial nerves are rare and thought to be radioresistant. We report a case of a MES involving the Vth and VIIth cranial nerves responsive to radiotherapy. A 41-year-old man with progressive left facial weakness underwent an MRI that disclosed an enhancing lesion involving both V3 cranial nerve and the distal VIIth nerve. Biopsy confirmed a malignant epithelioid schwannoma. The tumor was resected but residual tumor was present at the cut end of the infraorbital nerve, within the oral cavity and at the brainstem. Positive excision margins were irradiated to 60 Gy/30 fractions by a wedge pair technique extending from the inferior orbit to C2. Tumor was controlled for 38 months and then radiographic recurrence was resected from the infratemporal fossa outside the irradiated field.A new primary MES tumor developed at 69 months at the C1/C2 root levels at the lower edge of the previously irradiated field. It was subtotally resected but by 77 months residual tumor had grown inferiorly down to C5 so this area was re-irradiated with a complicated 7-field approach to spare spinal cord. Initially the tumor responded but ultimately progressed posteriorly where radiation dose was limited by spinal cord tolerance. New involvement of the Xth cranial nerve was noted. The patient expired from brainstem compression 7 years after initial radiotherapy. The long-term control of the original tumor despite positive margins argues for the use of radiotherapy in the treatment of these tumors.