Primary leptomeningeal melanomatosis successfully treated with PD-1 inhibitor pembrolizumab

Rationale: Primary leptomeningeal melanoma is an extremely rare disease of the central nervous system. There are no standard treatment protocols with a poor prognosis in very few reported cases. Immunotherapy in primary brain melanoma has not been successfully applied so far. Patient concerns: We describe a female patient 72-year-old diagnosed in the Neurosurgery Department which presented with generalized seizures. Diagnoses: Histological examination confirmed atypical melanocytes immunohistochemically positive for melan A, HMB45 and S-100 protein in the meninges, BRAF V600E negative. Dermatological, ophthalmological examinations, and 18-FDG PET/CT were negative. Interventions: The patient was successfully treated with pembrolizumab 2 mg/kg every 3 weeks for 2 years. Outcomes: The disease was stable for 2 years and the patient had no significant toxicity. Lessons: Our report describes durable intracranial tumor response suggesting the efficacy of PD-1 inhibitor pembrolizumab for central nervous system primary leptomeningeal melanoma.