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, pleomorphisrn, increased mitotic activity and invasive growth. Ultrastructurally, inter‐digitating 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 β subunit. Most tumor cells were positive for LY subunit of S‐100 protein. This is the eighth reported case of malignant schwannoma arising in the intracranial trigeminal nerve. Acta Pathol Jpn 40: 219‐225, 1990.