Incidence and Mortality
Melanoma of the uveal tract (iris, ciliary body, and choroid), though rare, is the most common primary intraocular malignancy in adults. The mean age-adjusted incidence of uveal melanoma in the United States is approximately 4.3 new cases per million people, with no clear variation by latitude. Males have a higher incidence than females (4.9 vs. 3.7 per million). The age-adjusted incidence of this cancer has remained stable since at least the early 1970s.[1,2] U.S. incidence rates are low compared with the rates of other reporting countries, which vary from about 5.3 to 10.9 cases per million. Some of the variation may be the result of differences in inclusion criteria and methods of calculation.
Uveal melanoma is diagnosed mostly at older ages, with a progressively rising, age-specific, incidence rate that peaks near the age of 70 years.
Host susceptibility factors associated with the development of this cancer include:[2,3,4]
- Caucasian race.
- Light eye color.
- Fair skin.
- The ability to tan.
In view of these susceptibility factors, numerous observational studies have attempted to explore the relationship between sunlight exposure and risk of uveal melanoma. To date, these studies have found only weak associations or yielded contradictory results. Similarly, there is no consistent evidence that occupational exposure to UV light or other agents is a risk factor for uveal melanoma.[3,5]
Uveal melanomas can arise in the anterior (iris) or the posterior (ciliary body or choroid) uveal tract. Iris melanomas have the best prognosis, whereas melanomas of the ciliary body have the least favorable prognosis. Most uveal tract melanomas originate in the choroid. The ciliary body is less commonly a 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, i.e., they tend to be small, slow growing, and relatively dormant in comparison with their posterior counterparts. Iris melanomas rarely metastasize. Melanomas of the posterior uveal tract generally have a more malignant, histologic 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.