Diagnostic challenge: primary leptomeningeal melanoma with melanomatosis, illustrative case report.

Primary leptomeningeal melanoma is an extremely rare type of intracranial melanoma. It cannot be reliably distinguished from metastatic melanoma on neuroimaging and histopathological characteristics alone; its diagnosis is established only after exclusion of secondary metastatic disease from a cutaneous, mucosal or retinal primary. Prognosis is poor, partly due to its high rate of misdiagnosis. Herein, we report a case of a primary meningeal melanoma of the skull base with melanomatosis, in a 31-year-old man, mimicking meningioma. Our aim is to highlight the diagnostic pitfalls and to discuss the histopathological differential diagnoses, especially with other pigmented lesions of central nervous system.