Primary meningeal melanomatosis

Meningeal melanomatosis is an extra-axial well-encapsulated malignant tumor with diffuse meningeal growth and dark coloration (due to high melanin contents), while meningeal melanocytoma is the focalized benign variant. Melanocytic tumors may be secondary to melanoma or be histologically benign, however, their diffuse nature makes them impossible to cure. Melanocytosis is a diffuse tumor that can form solitary extra-axial tumors, which invades the parenchyma and presents signs of malignancy with increased mitosis and Ki67, observed in 1 to 6% of immunopathological exams. Melanoma of the leptomeninges, presents signs of malignancy with anaplastic cells, which cluster in fascicles of melanin in the cytoplasm, with more than 3 atypical mitoses per field and Ki67 presenting in more than 6% of the immunopathological fields analyzed ¹⁾.

Dacarbazine (16–20% efficacy) combined with radiotherapy and chemotherapy has recently proven to be the most effective treatment for melanomatosis.

A case of a patient with long-term meningeal melanomatosis, with progressive neurologic deficit and characteristic radiologic features ²⁾.