Meningeal melanocytoma. Report of a case and a historical comparison.

Abstract

Meningeal melanocytomas are rare tumors of the central nervous system that are found almost exclusively in the posterior fossa and spinal cord and whose natural history is poorly defined. In this report, the authors review the clinical presentation, radiological appearance, operative findings, and histological features in two cases of meningeal melanocytoma: one cranial and one spinal. Two women, aged 21 and 30 years, were admitted to the hospital 60 years apart: the first because of progressive paraplegia and the second because of slowly progressive hearing loss. The first patient had an extradural tumor that was treated by laminectomy, subtotal resection, and postoperative radiotherapy in 1936. Her symptoms recurred 16 years later and she underwent reoperation of the residual tumor, which was found to have an intradural component. The authors' patient, who presented 60 years later, underwent plain and enhanced computerized tomography and magnetic resonance imaging that demonstrated a large posterior fossa lesion indicative of either an acoustic neuroma or a meningioma. She underwent posterior fossa decompression but only partial excision of the tumor could be accomplished because vigorous bleeding limited the extent of the resection. Surgery was followed by radiotherapy. The residual tumor enlarged despite these measures and required repeated resection 6 months later. At the second operation the tumor was much less vascular, perhaps reflecting the effects of radiotherapy, and was removed almost entirely. The patient died 6 months later from an anticoagulant-related cerebellar hemorrhage. In both cases the lesions were jet black, and histological examination revealed melanin-containing hypercellular tumors with rare mitotic figures. Meningeal melanocytomas are being diagnosed with increased frequency in parallel with improvements in neuroimaging and clarification of histological features. Clinical presentation of patients with these tumors typically occurs in their fifth decade and women are affected twice as often as men. The posterior fossa lesions can mimic acoustic neuromas and meningiomas in location and radiological appearance; however, the internal auditory canal is normal. In the spine, meningeal melanocytomas present with the clinical features of myeloradiculopathy. Diagnosis is made intraoperatively from the gross, jet-black appearance of the tumor and from histological examination. Vascularity, size, and location may render complete resection unfeasible. Because of the tumor's propensity to recur, radiotherapy has been recommended but its role remains to be elucidated.