Primary meningeal malignant melanoma
Primary meningeal malignant melanomas, or merely meningeal melanoma, is a primary melanocytic tumour of the CNS and represent malignant neoplasms of the leptomeningeal melanocytes, derived from neural crest cells.
Unlike meningeal melanocytosis, which is diffuse, meningeal melanoma presents as a solitary mass.
Meningeal melanomas are encountered in all age groups 1.
These durally based extra-axial tumours occur anywhere in the central nervous system, but appear to have a predilection for the spinal cord and posterior fossa, similar to meningeal melanocytomas 1.
Meningeal melanomas appear as circumscribed masses of variable pigmentation from black to non-pigmented 1.
Microscopically, meningeal melanomas appear similar to malignant melanomas elsewhere in the body. They demonstrate cellular pleomorphism and atypia, necrosis and are mitotically active, features which are helpful in distinguishing them from meningeal melanocytomas 1.
- HMB45: positive
- melan-A: positive
- MITF: positive
- S100: positive
- vimentin: variable
- neuron-specific enolase: variable
- GFAP, NFPs, cytokeratins, EMA: usually negative
These tumours appear as extra-axial masses, with enhancement on both CT and MRI. They may have variable T1 signal hyperintensity depending on the degree of melanin present.
Treatment and prognosis
Meningeal melanomas are aggressive lesions with a generally poor prognosis, although as they are localised, they have a better prognosis than melanoma metastases to the dura 1.