MENINGEAL MELANOCYTOMA - AN UNCOMMON DIAGNOSTIC PITFALL IN SURGICAL NEUROPATHOLOGY

Objective.-To describe the neuropathologic findings in four cases of m eningeal melanocytoma, a rare benign melanocytic tumor of the central nervous system. Design.-Retrospective analysis of surgical pathology a nd autopsy material. Results-Grossly, all four tumors were well-circum scribed pigmented lesions, and three of four were attached to dura. Mi croscopically, the neoplasms were composed of spindle cells with epith elioid foci. Mitoses were not seen and only one case exhibited minimal necrosis. Immunohistochemistry and electron microscopy demonstrated t he melanocytic nature of the lesions; all four cases showed S100 prote in and neuron-specific enolase staining, and three cases exhibited mel anoma-specific antigen staining. Immunostaining for epithelial markers and vimentin was uniformly negative. The single case in which electro n microscopy was performed demonstrated premelanosomes. Conclusions.-M eningeal melanocytoma is a benign pigmented neoplasm that can easily b e confused with melanoma, especially on frozen section analysis. Pract icing surgical pathologists should be aware of this entity.