Melanocytic Tumors

Melanocytic Tumors

Meningeal Melanocytosis

Definition: Melanocytic tumors are a rare variant of primary central nervous system (CNS) melanomas that comprise two distinct phenotypes: diffuse melanocytosis and melanomatosis to well-differentiated melanocytoma and melanoma. Diffuse melanocytosis is confined to the subarachnoid space, but melanomatosis can extend into the perivascular spaces with a superficial invasion of the neighboring brain.

Epidemiology: The estimated incidence of meningeal melanocytic tumors is 0.9 per 10 million and can affect any age group. Gender predilection is not known because of its rarity.

Clinical features and standard therapy: Although histologically benign, meningeal melanocytosis can be clinically and biologically aggressive. Complete surgical resection is curative for most cases. Radiation therapy is used after incomplete resection of tumor because recurrence rate is high in residual tumor.


Meningeal melanocytosis is a diffuse tumor that infiltrates leptomeninges but remains within the subarachnoid space. Diffuse enhancement of the leptomeninges on imaging can mimic subarachnoid hemorrhage, pus, or metastatic tumor.