Case report of a rare primary intracranial malignant melanoma, reviewing the literature and guidance for management

Primary intracranial malignant melanoma (PIMM), is a rare intracranial malignancy arising from melanocytes lining leptomeningeal tissue. It accounts for approximately 1% of all melanomas and 0.07% of all brain malignancies (1). It can be classified into 2 types—diffuse meningeal melanomatosis or solitary (discrete) solid tumours depending on imaging pattern (2). PIMMs rarely metastasize beyond the central nervous system (CNS) and are histologically similar to melanomas of other sites. They are often diagnosed after excluding the presence of extracranial lesions from careful physical examinations and positron emission tomography-computed tomography (PET-CT) imaging. Specific molecular mutations in GNAQ and GNA11 genes may also be helpful to distinguish PIMMs from metastatic melanoma (3,4). Given the rarity of this disease, there are no standard management guidelines and most of the evidence for treatment comes from shared experiences of case reports or are inferred from the treatment of metastatic melanoma. We present a recent case experience in accordance with the CARE reporting checklist (available at https://tro.amegroups.com/article/ view/10.21037/tro-21-32/rc) and referenced the evidence to guide our management decisions. Case Report