An extramedullary, parasagittal tumor in a 55-year-old male

This intracranial, parasagittal, well-circumscribed, contrast-enhancing mass in a 55-year-old male was thought radiologically to be a meningioma. Cursory inspection at low-power reveals some architectural whirling of cells (above), suggestive of meningioma. However, inspection of other areas (below) show many cells heavily burdened with neuromelanin. This finding of course raises the spectre of metastatic or primary melanoma. But since there are no malignant histomorphologic features, and the immunohistochemical MIB-1 proliferation index is less than 1%, the diagnosis is melanocytoma -- a benign proliferation of native leptomeningeal melanocytes. The meningeal melanocytoma is akin to the blue nevus of the skin.