Discussion Author: Paul J. Shogan
Choroidal melanomas are the most common primary intraocular tumors in adults, and the most commonly occurring uveal melanoma. The uvea is subdivided into the iris, the ciliary body, and the choroids. Most choroidal melanomas are believed to develop from preexisting melaanocytic nevi. The estimated prevalence is five to seven cases per 1 million adults, occurring most commonly in people of northern European descent. Sixty-five percent of melanomas occur in those older than 50 years. Patients may be asymptomatic with lesions discovered during a routine ophthalmologic examination. Other patients may notice vision loss, photopsia, and visual field deficits.
Melanomas primarily metastasize to the liver, as well as to the lung, bone, kidney, and brain. Treatment is dependent on site of origin, size, location of the primary lesion, and on the presence of extraocular extension, recurrence, or metastases. Melanomas greater than 1 cm in thickness are managed with enucleation. Medium sized lesions (3 mm to 1 cm) may be managed with enucleation, plaque brachytherapy and external-beam radiation. Small tumors (<3 mm in thickness) are monitored every 3-6 months with US.
Uveal melanomas are usually assessed by ophthalmologic examination, fluorescein angiography, US, CT or MR imaging. On unenhanced CT, these lesions appear elevated, hyperdense, are sharply marginated, and following contrast administration avidly enhance. At MR imaging, most melanomas appear as well-defined solid masses that are hyperintense on T1-weighted images, and hypointense on T2-weighted images secondary to the paramagnetic effects of melanin. Contrast enhanced fat-suppressed MR images are useful to demonstrate scleral invasion, tumor extension to the optic disc, and extraocular invasion.
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