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

## TL;DR

A rare brain tumor transformed into melanoma, and early immunotherapy improved short-term outcomes, according to a case report.

## Contribution

The study highlights the potential benefit of early immunotherapy in malignant transformation of meningeal melanocytoma.

## Key findings

- Early immunotherapy within one month of malignant transformation was linked to better short-term outcomes.
- Delayed or absent immunotherapy provided little benefit in controlling the disease.
- Sequential use of dual-agent immunotherapy modestly extended disease control in this case.

## Abstract

Primary meningeal melanocytoma is a rare tumor that can occasionally transform into an aggressive melanoma, but there are no clear treatment guidelines. We describe a woman who initially had a benign melanocytoma that later had malignant transformation with multiple organ metastasis. The patient received immunotherapy early after malignant transformation; the response was temporary. By reviewing all similar cases, we found that early initiation of immunotherapy—within one month of malignant transformation—was associated with better short-term neurological and functional outcomes, while delayed or absent therapy offered little benefit. This case underscores the importance of recognizing malignant transformation promptly and considering early immunotherapy, even in rapidly proliferating tumors, to improve disease control.

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.