Primary Malignant Meningeal Melanoma Complicated by Cerebral Venous Sinus Thrombosis: An Illustrative Case With a Systematic Review of the Literature

Melanocytic tumors of the central nervous system (CNS) such as meningeal melanoma are exceedingly rare tumours derived from leptomeningeal melanocytes. We report an illustrative case of a previously healthy 47- year-old male who presented with tonic-clonic seizure. Magnetic resonance imaging (MRI) with contrast demonstrated a homogenously enhancing right temporal extra-axial lesion. The patient was stabilized on anti-epileptic medications and dexamethasone prior to proceeding with complete surgical resection of the lesion. Intraoperatively, the lesion was heavily pigmented with invasion of the surrounding dura and skull. Histopathology revealed a poorly differentiated neoplasm with nuclear atypia and melanin-containing cells with strong SOX10 and variable S100 positivity. Computed tomography (CT) of the chest, abdomen, and pelvis showed no metastatic disease, and molecular profiling was negative including absent BRAF mutation. He began checkpoint inhibitor therapy and subsequently developed cerebral venous sinus thrombosis managed with anticoagulation. Sixteen months post-operatively, he was neurologically intact, working fulltime, and had resumed immunotherapy. We systematically reviewed the literature on primary intracranial malignant melanoma (PIMM) with the goal of understanding the prognosis and best treatment options for this disease. Our systematic review produced 82 articles (118 unique cases) of PIMM. The average age at diagnosis was 45.9 years (95% CI:42.9-48.9), and headache (54.2%) was the most common initial presentation. Eighty-nine percent of patients had primary surgical resection, and 41.0% of these individuals experienced a recurrence with a mean time to recurrence of 19.6 months (95% CI:6.95-32.23). Adjuvant therapy was administered in 65.7% of surgically resected patients; including radiotherapy, chemotherapy, immunotherapy, or a combination. In summary, PIMM is a rare tumour that can appear radiographically similar to meningioma. The results of our systematic review demonstrate that surgical resection remains the mainstay of therapy for best long-term prognosis.