Primary versus Secondary Central Nervous System Melanoma: a Diagnostic Dilemma and Report of a Case

Malignant melanoma is a cancer of melanocytic origin, typically cutaneous. Despite recent advances, the prognosis is poor. Brain metastases occur in approximately 7-16% of cases and leptomeningeal metastases in 5-7%. Primary central nervous system (CNS) melanoma is rare, accounting for 1% of all melanoma cases and 0.07% of brain tumors. Methods: A 65-year old man presented with haemorrhagic venous infarction of the left temporal lobe, leading to reversible motor aphasia and right-sided hemiparesis. Brain magnetic resonance imaging also revealed peculiar supratentorial cerebral and meningeal lesions suggesting neoplasia or vasculitis. Ancillary tests were unremarkable, a brain biopsy was proposed, but the patient declined. After 1.5 years symptoms recurred and imaging studies found progression of lesions, with necrosis and surrounding vasogenic oedema. The patient finally agreed to a brain biopsy for conclusive diagnosis. Results: Histopathological and immunohistochemical assessment was consistent with malignant pigmented melanoma. There were no suspicious primary lesions, but the patient recounted having had a thoracic skin lump excised some years prior, allegedly benign, yet unavailable for second opinion. Conclusion: In suspicious CNS presentations, histopathological reevaluation of previously excised skin lesions is advised, especially if brain biopsy cannot be performed. Albeit rare, primary CNS melanoma should also be considered