Amelanotic melanocytoma of the sella mimicking pituitary adenoma.

We describe a 50-year-old man with a well-demarcated intra- and extrasellar lesion and clinical signs of a non-functioning pituitary adenoma. Neuropathological examination revealed tumor composed of non-pigmented spindle cells arranged in tightly packed nests separated by delicate vascular septae. There was no significant cellular atypia or mitotic activity, and Ki67-positive nuclei were present in less than 1% of cells. The neoplastic cells were positive for S-100 and vimentin, and negative for numerous cellular markers including HMB45, anti-melanoma cocktail antibodies, and Masson melanin stain. Electron microscopy revealed scattered cells with small numbers of premelanosomes, aiding in the correct diagnosis of an amelanotic melanocytoma. This is the first case report of entirely amelanotic melanocytoma of meninges, and in a very unique location. BRAF was negative supporting the diagnosis of intracranial origin of the tumor. Approximately 2 years after subtotal resection and stereotactic radiosurgery the patient is alive and well with a non-progressive residual tumor.
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