Diagnostic methods and therapeutic options of uveal melanoma with emphasis on MR imaging-Part I: MR imaging with pathologic correlation and technical considerations.

Uveal melanoma is a malignant neoplasm that derives from pigmented melanocytes of the uvea and involves, in order of decreasing prevalence, the choroid, ciliary body and iris. Its prognosis is related to histopathologic and genetic features, tumor size and location, extraocular extension. The diagnosis is fundamentally based on clinical evaluation (ophthalmoscopy, biomicroscopy) and ultrasonography. MRI is useful in case of untransparent lens or subretinal effusion. Moreover, MRI has a significant role to confirm the diagnosis, in the evaluation of the local extent of the disease with implications for treatment planning, and in the follow-up after radiotherapy treatment. Uveal melanoma can show different morphologic features (lentiform, dome or mushroom shape) and often determines retinal detachment. MR appearance of uveal melanoma mainly depends on the melanin content. Uveal melanoma typically displays high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. Nevertheless, imaging appearance may be variable based on the degree of pigmentation and the presence of areas of necrosis or cavitation. Differential diagnosis includes other uveal lesions. The radiologists and in particular MRI play a significant role in the clinical management of uveal melanoma. The purpose of this pictorial review is to provide the radiologists with awareness about diagnostic methods and therapeutic options of uveal melanoma. In the present first section we summarize the MR anatomy of the eye and describe ophthalmological and radiological imaging techniques to diagnose uveal melanomas, with emphasis on the role of MR imaging. Additionally, we review MR imaging appearance of uveal melanomas.