Primary melanocytoma arising from the thoracic leptomeninges case

Primary melanocytoma arising from the leptomeninges of the spinal cord is v ery rare. A surgical specimen of a thoracic meningeal tumor was resected fr om a 75-year-old woman complaining of gait disturbance was investigated. Ma gnetic resonance imaging and myelography showed a dumb-bell-type tumor in t he subdural space at the Ist to 2nd thoracic vertebrae. The tumor was subto tally resected because of adhesion to the lamina and thoracic medulla. The localized, gelatinous black tumor showed a well-defined margin without diss emination or infiltration. The tumor had a thin capsule and was composed of solid proliferation of neoplastic melanocytes. Neither whorl formation nor foci of palisaded nuclei were observed. The neoplastic cells were of two m ajor types: an epithelioid- or polygonal-shaped type and a spindle-shaped t ype, and had a large nucleus, a prominent nucleolus, coarse chromatin, and melanin-pigments in their cytoplasm. Only a few mitotic figures were observ ed. They were positive for HMB-45 and S-100 protein. This case was consider ed to be primary melanocytoma arising from the thoracic leptomeninges.