Primary malignant melanoblastosis of the meninges. Clinical, cytologic and neuropathologic findings in a case.

A 66-year-old man presented with a six-month history of neurologic symptoms suggestive of a craniospinal tumor or a diffuse inflammatory process in the subarachnoid space. Cytologic examination of cerebrospinal fluid (CSF) revealed inflammatory changes and malignant melanin-containing cells, leading to a diagnosis of meningeal spread of a melanoma. There was no history of skin excisions and no clinical evidence of primary melanoma of the eye. Neuroradiologic investigations, including CT and myelography, to confirm the diagnosis were negative. Despite intrathecal cytostatic therapy, the patient died eight months after the onset of symptoms. Autopsy disclosed diffuse meningeal melanoblastosis of the spinal cord and the base of the brain, confirming the cytologic diagnosis. In addition, two micrometastases in the liver were found as only extraneural manifestation. This case emphasizes the importance of CSF cytology in the diagnosis of diffuse infiltrating processes in the subarachnoid space.