Epidemiology of skin cancer

Skin cancers can be broadly classified into two types, melanomas and non-melanomas. Melanomas are cancer of the melanocytes, which lie in the basal layer of the epidermis. Melanomas, unless detected at an early stage have a high fatality rate. Non-melanocytic skin cancers include two major types, basal cell carcinomas and squamous cell carcinomas (SCCs). Both of these forms of skin cancer are relatively benign; however, if neglected they can result in significant morbidity and, in some cases, death (especially from SCC).

The incidence of skin cancer is rising among fair-skinned populations throughout the world with the highest rates in Australia. People whose skin burns easily are at the highest risk. The principle aetiological factor for skin cancer is ultraviolet (UV) radiation, mainly from the sun's rays (Marks & Hill, 1992; IARC, 1992). Around two-thirds of daily UV radiation is transmitted in the two hours each side of true midday. In tropical areas, UV levels are high all year round. In temperate zones, UV levels only reach high levels in the summer months, except at high altitudes, or in reflecting environments where the levels can be much higher than normal. Nonetheless, some sun exposure is important for production of Vitamin D and total sun avoidance is not recommended. Vitamin D deficiency causes various bone diseases and may increase risk of immune disorders and even cancer (Vanchieri, 2004; Luca & Ponsonby, 2002).

There is no clear consensus on the mechanisms by which UV radiation leads to skin cancers.