PATH-43. MALIGNANT TRANSFORMATION OF MENINGEAL MELANOCYTOMA - GENETIC ALTERATIONS AND RESPONSE TO CHECKPOINT BLOCKADE IMMUNOTHERAPY

Abstract

Abstract INTRODUCTION Meningeal melanocytomas are uncommon tumors that develop from leptomeningeal melanocytes. These tumors can exhibit aggressive behavior, leading to symptoms due to compression and potential invasion of nearby central nervous tissue. Case: In this report, we discuss the case of a 45-year-old man who was diagnosed 18 years ago with a meningeal melanocytoma in the right temporal region. He underwent complete resection with each recurrence and received focal intensity-modulated radiation therapy after a third recurrence in 2013. In May 2022, he developed progressive headaches and diplopia secondary to tumor recurrence on the right temporal region. Resection revealed that the tumor had progressed to malignant meningeal melanoma with 34 mitoses per 10 high-power fields. Next-generation sequencing (NGS) showed GNAQ mutation confirming tumor of central nervous system (CNS) origin, and also showed an SF3B1 mutation, indicating aggressive behavior. Several chromosomal abnormalities were also detected. Systemic workup revealed liver, lung, and bone metastasis. Liver biopsy confirmed meningeal melanoma of central origin. The patient received radiosurgery with a total of 30Gy over five fractions to intracranial surgical cavity, followed by three cycles of nivolumab and relatlimab. Unfortunately, the patient experienced severe intracranial and systemic progression, leading to his death six months after the malignant transformation. DISCUSSION Meningeal melanocytomas are rare however these tumors have a high recurrence rate with potential malignant transformation over time. NGS is a valuable tool for confirming the CNS origin of the tumor and predicting its aggressive behavior. Despite microscopic similarity with cutaneous melanomas, meningeal melanocytomas have different pathogenesis and do not seem to respond to immunotherapy, as observed in this case.