A case report on intermediate-grade malignant meningeal melanocytoma with elevated cell proliferation index.

Meningeal melanocytoma is a kind of extremely rare pigmented tumor of the central nervous system, which often occurs in the groove around the base of the brain and spinal pia mater. Age of onset is 40 to 50 years old, mostly presenting a benign course of disease and the prognosis is good. Case reports of partial invasion or metastasis from lesions are even rarer. This report described a case of 56-year-old meningeal melanoma patient with partial skull and muscle invasion at the lantooccipital transition zone. Intraoperative histological examination showed moderate malignancy and Ki-67 index was 10%.