Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
JULY 2012
Next Case of the Month coming August 6...
Primary Malignant Melanoma
- Primary malignant melanomas of the cerebello-pontine angle usually present with cerebellar dysfunction and can occur in any age group. Melanocytes are normally present in intracranial leptomeninges, usually in the posterior cerebral fossa, and can give rise to benign (meningeal melanocytoma) or malignant (malignant melanoma) tumors.
- Key Diagnostic Features: CT: Melanotic lesions appear as well circumscribed, isoattenuating-to-hyperattenuating extraaxial tumors that demonstrate homogenous enhancement following contrast administration. MRI: On MRI, signal intensity characteristics of the lesion depend on the amount of melanin within the tumor. Melanin shortens T1 and T2 relaxation times, and so melanocytic neoplasms appear isointense- or hyperintense-to-normal brain tissue on T1-weighted images and isointense or hypointense on T2-weighted images. They intensely enhance after intravenous administration of contrast. Occasionally, intralesional hemorrhage can be seen.
- DDx: Meningioma, desmoplastic medulloblastoma, metastasis, schwannoma, endolymphatic sac tumor, hemangioblastoma
- Rx: Surgery, radiation therapy
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