Monday, June 22, 2009

An extramedullary, parasagittal tumor in a 55-year-old male

This intracranial, parasagittal, well-circumscribed, contrast-enhancing mass in a 55-year-old male was thought radiologically to be a meningioma. Cursory inspection at low-power reveals some architectural whirling of cells (above), suggestive of meningioma. However, inspection of other areas (below) show many cells heavily burdened with neuromelanin. This finding of course raises the spectre of metastatic or primary melanoma. But since there are no malignant histomorphologic features, and the immunohistochemical MIB-1 proliferation index is less than 1%, the diagnosis is melanocytoma -- a benign proliferation of native leptomeningeal melanocytes. The meningeal melanocytoma is akin to the blue nevus of the skin.

6 comments:

Anonymous said...

Could you post the relevant MRI images Brian? Melanocytomas I have seen, and most descriptions of these, have them as intra-axial lesions, mostly in the cortex, and not extra-axial meningioma-like masses. So I'd be interested in seeing the MRI scans before making a final judgment on the real nature of this tumor. Thanks--Douglas C Miller MD,PhD

Brian E. Moore, MD said...

I wish I could provide the MRI, Doug. But this is actually a case I looked at with Dr. Peter Burger at Hopkins when I did a short rotation with him during my fellowship a few years back. (I am posting it now because I was going over a case with a resident recently and the issue of melanocytoma came up.) This case was sent to Dr. Burger from a pathologist in Dusseldorf, Germany with an accompanying cover letter saying that the radiological impression was that of extra-axial meningioma. But there were no MRI images sent with the slides. The pathologic diagnosis of melanocytoma was made by Burger.

aspiring neurochic said...

The second picture is that hmb45 or mela or something else like s100.

Brian E. Moore, MD said...

The second picture is simply that of an H&E stained slide. The pigment is endogenous melanin.

Agent 86 said...

My impression is that primary intra-axial melanocytic tumors are the exception:

Brat DJ, Giannini C, Scheithauer BW, Burger PC. Primary melanocytic neoplasms of the central nervous systems. Am J Surg Pathol. 1999 Jul;23(7):745-54.

Interesting thing is that the behavior of these tumorous primary melanocytic lesions is only loosely linked to histology. Long-term recurrence free survival is not uncommon with primary meningeal melanomas.

The dark side of the coin is that for those unfortunate patients who present with a melanocytosis pattern of growth, benign cytology is no consolation, as inexorable spread and poor response to therapy is virtually universal.

It seems that with melanocytic CNS tumors, we're further away than an MRI from knowing their real nature.

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