label: Meningeal Melanocytosis
label_lc: meningeal melanocytosis
description: A diffuse or multifocal proliferation of uniform nevoid polygonal cells in the leptomeninges. Cells may spread into the Virchow-Robin spaces without frank invasion of the brain. Diffuse melanocytosis carries a poor prognosis even in the absence of histologic malignancy. (WHO)