Malignant schwannoma arising in the intracranial trigeminal nerve. A report of an autopsy case and a review of the literature.

An autopsy case of malignant schwannoma arising in the intracranial trigeminal nerve is reported. The tumor involved the right cerebellopontine angle of the brain stem in an 18-year-old man. The spindle-shaped tumor cells with eosinophilic cytoplasm proliferated in fascicles and exhibited hypercellularity, pleomorphism, increased mitotic activity and invasive growth. Ultrastructurally, interdigitating cytoplasmic processes and a few fragmented basal lamina-like structures were observed. Immunohistochemically, some tumor cells were reactive with conventional anti-S-100 protein antibody, but negative for beta subunit. Most tumor cells were positive for alpha subunit of S-100 protein. This is the eighth reported case of malignant schwannoma arising in the intracranial trigeminal nerve.