Progress in the studies of etiology, epidemiology and pathogenesis of ocular melanomas

Our population-based epidemiological studies demonstrated that the epidemiological aspects of ocular melanomas are different from those in cutaneous melanoma. The incidences of conjunctival melanoma increased in the past decades and was higher in the South (greater sun exposure), which is consistent with the occurrence of cutaneous melanoma. On the contrary, incidences of uveal melanoma are in the opposite direction of cutaneous melanomas. This indicates that solar radiation does not cause an increase of incidences of melanoma in ocular tissues (uveal melanoma) that are not exposed to solar radiation. Solar radiation increases the incidence of melanoma only in tissues exposed to said radiation, such as in conjunctival and eyelid melanomas. Uveal melanoma incidences in light-pigmented individuals are much greater than in dark-pigmented individuals. This result cannot be attributed to a melanin photo-screening effect, and is possibly related to melanin's biophysical and biochemical effects. The difference in incidences between light- and dark-pigmented individuals in conjunctival melanomas, as well as in vulvar and vaginal melanomas, are much lower than that in the uveal and cutaneous melanomas. This difference may be related to the different histological structures in these melanomas; conjunctival and vaginal melanomas occur in the mucous membrane, whereas cutaneous melanomas occur in the skin. Recent molecular biological studies indicate that each type of melanoma has its own molecular changes which are different from the others. Therefore, independent studies are required for each type of melanoma to discover their own etiology and pathogenesis, and to develop relevant novel prevention and treatment procedures.