Meningeal melanocytoma. Report of a case and review of the literature.

A primary localized, partly encapsulated melanotic tumour broadly attached to the occipital dura and tentorium was removed from a 27 year-old woman. It recurred almost four years later in the posterior fossa and was resected again. Although grossly resembling a meningioma, the tumour lacked the histological, immunocytochemical and ultrastructural features of meningiomas and was characterized by the presence of numerous melanosomes and premelanosomes in the cytoplasm of tumour cells and macrophages and was, therefore, classified as "meningeal melanocytoma". The clinical and pathological features of this and 15 other cases in the literature are reviewed. The neoplasm, mainly occurring in the posterior cranial fossa and spinal canal, may cause neurological deficits through expanding, but non-invasive growth. Its biological behaviour is variable, and recurrence may occur after incomplete resection, but transition into malignant melanoma has not been observed. Total resection of this rare pigmented tumour arising from the pial melanocytes is recommended.