Primary Intracranial Meningeal Melanocytoma with Malignant Transformation: A Case Report and Comparison of Early Versus Late Immunotherapy Interventions.

Primary meningeal melanocytoma is an uncommon, pigmented neoplasm that rarely undergoes malignant transformation, and therapeutic guidelines remain undefined. We report a 43-year-old woman who initially presented with a sudden headache and a right temporal intraparenchymal mass. Subtotal resection revealed a melanocytoma (WHO grade I); residual tumor was treated with Gamma Knife. About 15 months later, she deteriorated rapidly due to malignant transformation with cerebral hemorrhage and spinal leptomeningeal metastasis. Pembrolizumab was initiated within four weeks of the malignant diagnosis and produced transient neurological improvement. Due to symptomatic progression, ipilimumab plus nivolumab was commenced and achieved temporary radiographic stabilization, but the patient succumbed to diffuse progression later. Including this case, only five intracranial melanocytomas with malignant transformation treated with immune checkpoint inhibitors have been reported. Our experience supports initiating immunotherapy promptly after malignant transformation and suggests that sequential dual-agent blockade may modestly extend disease control.