ABSTRACT
Pigmented(melanotic) schwannoma is a very rare variant of schwannoma that characteristically has massive cytoplasmic melanin. Since it was described in 1946 by Bjorneboe, about 44 cases have been reported in the English literature. It has a relatively benign clinical course, but the cases arising in the cranial nerve and sympathetic chain show aggressive behavior with malignant potential. We herein report a typical case of pigmented schwannoma with light microscopic findings. The results of immunohistochemical and electronmicroscopic study are also presented. The patient was a 30 year-old Korean male who had a mass in his posterior neck for 10 years that recently.began to induce neurologic manifestations. The tumor, which was mainly in the extramedullary intradural space of the cervical canal extending to the extradural space and soft tissues of the neck, was relatively well defined and composed of black solid tissue. Microscopic, densely pigmented spindle cells forming fascicles, nuclear palisading, whorling and polygonal cells with vacuolated or clear cytoplasm were characteristic. Immunohistochemically, the tumor cells were positive for vimentin, S-100 protein, and HMB-45. Electron microscopic study revealed that the tumor cells have interdigitating cytoplasmic processes containing varying stages of melanosomes with a very focal basal lamina and Luse body like collagen bundles.