Contributor: Gordon K. Klintworth
Choroidal melanomas are malignant tumors that arise in the choroid 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 <20 years of age. Race is a major risk factor for choroidal melanomas and there is a propensity for white blue-eyed individuals. This tumor is the commonest primary intraocular malignant neoplasm in Causasians. Some lesions are thought to predispose to a choroidal melanoma (nevi [nevus - choroid], neurofibromatosis type I, the dysplastic nevus syndrome, congenital ocular melanocytosis, oculodermal melanocytosis), but acceptable statistical evidence to substantiate this belief is lacking The estimated rate of malignant transformation from choroidal nevi is 1/10,000-15,000 / year. As with other uveal melanomas those arising in the choroid are classified according to their cell type (revised Callender classification) into spindle A [melanoma - spindle A cell], spindle B [melanoma - spindle B], epithelioid [melanoma - epithelioid], intermediate [melanoma - intermediate cell], and mixed cell tumors [melanoma - mixed cell]. 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 ~3% of all choroidal intraocular melanomas. Based on their size choroidal melanomas can be classified clinically into three groups: small (<10 mm in diameter and <3 mm in elevation), medium-sized (10-15 mm in diameter and 3-5 mm in maximum thickness), and large (>15 mm in diameter and >5 mm thick) melanomas.