Contributor: Gordon K. Klintworth
Uveal melanomas are malignant tumors that arise in the uvea from melanocytes or their precursors. They are usually solitary and unilateral. Most develop in adulthood; the median age at diagnosis is 53 years. Only 1.6% of cases occur before twenty years of age. Race is a major risk factor for choroidal melanomas [melanoma - choroid] and there is a propensity for white blue-eyed individuals. This tumor is the commonest primary intraocular malignant neoplasm in Causasians, but like cutaneous melanomas [melanoma - skin], it is rare in Asians and other pigmented races in Africa and Latin America. In the United States it occurs 8.5-15 x more often in caucasians than in African Americans. Some lesions are thought to predispose to uveal melanoma (choroidal nevi [nevus - choroid], neurofibromatosis type I, dysplastic nevus syndrome, congenital ocular melanocytosis, oculodermal melanocytosis). The estimated rate of malignant transformation from uveal nevi is 1/10,000-15,000 / year. Uveal melanomas are classified according to their cell type (revised Callender classification) into spindle, epithelioid, intermediate, and mixed cell tumors. Most primary choroidal melanomas contain variable numbers of spindle A cells, spindle B cells, and epithelioid cells. Tumors composed entirely of epithelioid cells account for only about 3% of all choroidal intraocular melanomas. Melanomas can also be grouped according to pigmentation, reticulin fiber content, mitotic activity, rupture of Bruch membrane, transscleral extension, optic nerve extension, tumor shape, location, size, and morphometric analysis. Uveal melanomas can be divided into several different types: cavitary melanoma [melanoma - cavitary], diffuse melanoma [melanoma - diffuse], and necrotic melanoma [melanoma - necrotic].