October 8, 2020
A 22-year-old man with a history of numbness in right half of face with occasional clumsiness of right upper limb and gait ataxia for 2 months
Meningeal Melanocytoma
- Background:
- Meningeal melanocytomas are rare, benign, and slow-growing tumors arising from the normal melanocytic cells of the leptomeninges.
- These lesions are usually solitary and are located in the posterior cranial fossa, Meckel cave, or cervical and thoracic spinal canal, most likely due to the normally higher density of melanocytes in these locations.
- Clinical Presentation:
- Depends on the location of tumor and includes cranial nerve deficits, seizures, chronic basal meningitis, hydrocephalus, chronic spinal arachnoiditis, psychiatric disturbances, subdural/intracranial hemorrhage, myelopathy, and radiculopathy
- Key Diagnostic Features:
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On CT, these lesions are extra-axial, iso- to hyperattenuating, and enhance after administration of contrast material.
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On MR imaging, these lesions are iso- to hyperintense on T1WI relative to normal brain parenchyma, hypo- to isointense on T2WI, and show homogeneous enhancement.
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Lesions may show variable signal intensity due to varying amounts of melanin and a presence of intratumoral hemorrhage.
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- Differential Diagnoses:
- Meningeal melanocytoma is a rare condition and requires histologic correlation for definitive diagnosis.
- Pigmented meningioma: May demonstrate tumor calcification and hyperostosis of the adjacent bone, which would be unusual for melanocytoma
- Malignant melanoma of CNS: Similar imaging features; may be multifocal or disseminated rather than focal
- Melanotic schwannoma: May have calcifications, is hypo- to isointense on T1WI, iso- to slightly hyperintense on T2WI, and shows variable postcontrast enhancement
- Treatment:
- Complete surgical resection may be curative, but recurrence within 3 years of surgery has been reported in 22% of patients.
- Incomplete resection has a 50% chance of recurrence.
- Tumors that are not feasible for complete resection or show recurrence are treated with radiotherapy.
- Melanocytomas have been reported to have a potential for malignant transformation and distant metastasis.
