Skin cancer is generally divided into two main groups: non-melanoma skin cancer and melanoma. Melanoma is less common than NMSC, but the prognosis is far worse. Non-melanoma skin cancer is divided into two subtypes: Basal Cell Carcinoma (BCC) and Squamous Cell Carcinoma (SCC), and it is estimated that over 5 million new cases develop every year. Of these two types, BCC is more common.
Sun exposure has long been known to increase the risk of skin cancer: a term called photocarcinogenesis. A 2016 study showed that mice that consumed a high-fat diet were at increased risk of photocarcinogenesis and that a high-fat diet also increased the activity of inflammatory mediators in UVR-exposed skin and tumors. A prospective study of Nordic twins evaluated over time found that there is a genetic component to non-melanoma skin cancers and melanoma.
Non-Melanoma Skin Cancer
A report from 2016 in the journal Clinical Medicine (London) states that “exposure to UV radiation initiates approximately 90% of NMSC, causing malignant transformation of keratinocytes and suppression of the inflammatory response.”
A 2016 study from the journal Oncotarget mentions that chronic ultraviolet radiation (UVR) is associated with the development of SCC by inducing pro-inflammatory molecules, and a 2015 study relates the UVR-induced skin response to a deficiency in an enzyme, called TREX2, that is associated with DNA damage removal and degradation.
Sunburns and sun overexposure are clear risk factors for the development of non-melanoma skin cancers. There is a strong relation between SCC and constant or cumulative UVR exposure, and BCC is related to sunburns and high lifetime solar exposure.
For melanoma, it appears that gender is more specific to an increased incidence of development than chronic exposure to UVR. In men, it appears that sunburn risk is associated more with the development of melanoma than it is with BCC or SCC. The same study found that males with a history of sunburn on the trunk have an increased risk of developing melanoma, but the relationship is not as clear between BCC or SCC. In 2014, the journal Cutis published a study evaluating the risk factors for melanoma. The study found that people with lighter-colored skin types, frequent sunburns during childhood, and higher levels of education all had increased risks of developing melanoma. It is possible that the relationship between education and melanoma could be due to the fact that people with higher education may be able to take more vacations in which they have increased sun exposure. Future studies will hopefully evaluate this possible connection.
It is clear that prolonged exposure to UVR can increase the risk of developing all types of skin cancer, and the risk is higher in certain populations. All people should take preventive measures to avoid skin damage from the sun or artificial ultraviolet light, even if they are low risk. High-quality sunscreen, protective clothing, and shade-seeking behavior are all easy and necessary means of lowering the risk of cancer development.