Meningeal melanocytoma is an extremely rare pigmented tumor derived from leptomeningeal melanocytes. By and large it is considered to be a well-differentiated and slow-growing benign lesion. Generally, meningeal melanocytomas are solitary lesions, and the occurrence of the primary multifocal form in the central nervous system is exceedingly rare; it has been previously reported in only six cases.
Intracranial melanocytoma is usually a dural-based tumor, fed by dural arterial branches in a manner similar to meningioma. Primary sellar melanocytoma may be misdiagnosed as hemorrhagic pituitary macroadenoma, spindle cell oncocytoma, and intrasellar meningioma. These tumors differ in some radiological respects, but are difficult to differentiate preoperatively.
Only five cases of primary sellar/suprasellar melanocytic tumors, excluding melanomas have been reported thus far.
A 41-year-old woman with primary multifocal meningeal melanocytoma in the spinal canal. Contrary to earlier reports, the tumors presented with a scattered appearance mimicking neurofibromatosis.
On admission, the cerebral MR images of the patient were normal, whereas the spinal MR images showed scattered multifocal nodules mimicking neurofibromatosis. Surgical resection of the responsible lesions was scheduled. In addition to this case presentation, relevant previous reports were reviewed, and the challenging diagnosis, management, and prognosis of meningeal melanocytoma are discussed.
Gross total resection of the two largest lesions was achieved, and histopathological examinations confirmed the diagnosis. Despite the benign histopathological findings, the patient had an aggressive clinical course. On follow-up at 18 months after surgery, she succumbed to the disease.
Clinicians should be alert to a potential aggressive clinical course of meningeal melanocytoma, despite its benign histopathological nature. Of particular note is multifocality and diffuse leptomeningeal hyperpigmentation, which may suggest a poor prognosis. A combined treatment including surgical resection and adjuvant radiotherapy should be considered, and long-term close follow-up is necessary 1).
A 31-year-old woman presenting with a 2-year history of amenorrhea and an intrasellar mass with suprasellar extension, suggestive of hemorrhagic pituitary adenoma.
Transsphenoidal surgical excision was difficult due to extensive bleeding from the lesion, and at the time, the tumor could not be diagnosed histopathologically. Six years later, Sakata et al. operated again because of tumor regrowth. Angiography revealed a hypervascular tumor, which was fed from the dorsal sellar floor. We had difficulty resecting the tumor, but achieved total removal. These case had typical radiographic characteristics of melanocytoma, revealed by both magnetic resonance imaging and angiography. However, it was difficult to reach a final diagnosis. Further histopathological examination, including immunohistochemical and ultrastructural studies, was helpful for diagnosis of melanocytoma.
Primary sellar melanocytic tumors are derived from melanocytes in the meningeal lining of the sellar floor or in the diaphragm sellae, based on both embryological assumptions and the clinical findings of these case 2).