Anatomy

Uveal melanomas can arise in the anterior (iris) or the posterior (ciliary body or choroid) uveal tract.[6] Most uveal tract melanomas originate in the choroid. The ciliary body is a less common site of origin, and the iris is the least common. The comparatively low incidence of iris melanomas has been attributed to the characteristic features of these tumors; they tend to be smaller, slower growing, and relatively dormant compared with their posterior counterparts. Iris melanomas rarely metastasize.[7] Melanomas of the posterior uveal tract generally have a more malignant histological appearance; are detected later; and metastasize more frequently than iris melanomas. The typical choroidal melanoma is a brown, elevated, dome-shaped subretinal mass. The degree of pigmentation ranges from dark brown to totally amelanotic.

Most uveal melanomas are initially completely asymptomatic. As the tumor enlarges, it may cause distortion of the pupil (iris melanoma), blurred vision (ciliary body melanoma), or markedly decreased visual acuity caused by secondary retinal detachment (choroidal melanoma). Serous detachment of the retina may occur. If extensive detachment occurs, secondary angle-closure glaucoma occasionally develops. Clinically, several lesions simulate uveal melanoma, including metastatic carcinoma, posterior scleritis, and benign tumors, such as nevi and hemangiomas.[8]