A variety of appearances of malignant melanoma in the head: A review

Imaging is frequently requested to evaluate patients with malignant melanoma for metastases. When melanoma metastasizes to the head, the lesions can have a variety of appearances and can occur in a variety of locations. The usual appearances of malignant melanoma on magnetic resonance images include the melanotic and amelanotic patterns. The melanotic pattern consists of high signal intensity on TI-weighted images and low signal intensity on T2-weighted images. In the amelanotic pattern, the lesion is hypointense or isointense to the cortex on T1-weighted images and hyperintense or isointense to the cortex on T2-weighted images. However, there is frequent deviation from these patterns. Other patterns include small and rapidly growing metastases, miliary metastases, and subependymal metastases. Although the brain is the most common site of metastases to the head from melanoma, melanoma can metastasize to almost any intracranial or extracranial structure. Structures in the head that can be involved by metastases from melanoma include bone, muscle, the nasopharynx and mucosa, the parotid gland, the meninges, the choroid plexus, the internal auditory canal, and the orbit. The radiologist needs to be aware of these varied appearances and the relatively ubiquitous sites of involvement to better detect these lesions.