Meningeal melanocytoma (“melanotic meningioma”). Its melanocytic origin as revealed by electron microscopy

Abstract

A primary melanotic tumor of the leptomeninges with prolonged clinical course and benign histology was studied by light and electron microscopy. Similar tumors, referred to as “pigmented” or “melanotic” meningiomas, were reviewed. The cells of the tumor reported here lack the ultrastructural features of meningothelium and are characterized by the presence of numerous melanosomes and premelanosomes in their cytoplasm. Therefore, the term “meningeal melanocytoma” rather than “pigmented meningioma” appears appropriate. A benign histology and favorable clinical course distinguish meningeal melanocytoma from primary malignant melanomas of the leptomeninges. The histology, ultrastructure, and behavior of this tumor show similarities to melanocytic tumors of the dermis (cellular blue nevus) and of the uveal tract (spindle A melanoma). While cytologically and biologically benign, meningeal melanocytomas may cause neurologic deficits through their expanding growth; an early excision may be curative before neurologic complications become fatal.