Using artificial light for tanning was once believed to help prevent skin cancers, but it can actually lead to an increased incidence of melanomas.UV nail lamps, which are used in nail salons to dry nail polish, are another common and widespread source of UV radiation that could be avoided. Although the risk of developing skin cancer through UV nail lamp use is low, it is still recommended to wear fingerless gloves and/or apply SPF 30 or greater sunscreen to the hands before using a UV nail lamp.The body uses UV light to generate vitamin D so there is a need to balance getting enough sunlight to maintain healthy vitamin D levels and reducing the risk of melanoma; it takes around a half-hour of sunlight for the body to generate its vitamin D for the day and this is about the same amount of time it takes for fair-skinned people to get a sunburn. Exposure to sunlight can be intermittent instead of all at one time. Sunscreen
Sunscreen appears to be effective in preventing melanoma. In the past, use of sunscreens with a sun protection factor (SPF) rating of 50 or higher on exposed areas were recommended; as older sunscreens more effectively blocked UVA with higher SPF. Currently, newer sunscreen ingredients (avobenzone, zinc oxide, and titanium dioxide) effectively block both UVA and UVB even at lower SPFs. Sunscreen also protects against squamous cell carcinoma, another skin cancer.Concerns have been raised that sunscreen might create a false sense of security against sun damage.
From this point on, melanoma is capable of spreading. The Breslows depth of the lesion is usually less than 1 mm (0.04 in), while the Clark level is usually 2. The vertical growth phase (VGP) following is invasive melanoma. The tumor becomes able to grow into the surrounding tissue and can spread around the body through blood or lymph vessels. The tumor thickness is usually more than 1 mm (0.04 in), and the tumor involves the deeper parts of the dermis. The host elicits an immunological reaction against the tumor during the VGP, which is judged by the presence and activity of the tumor infiltrating lymphocytes (TILs). These cells sometimes completely destroy the primary tumor; this is called regression, which is the latest stage of development. In certain cases, the primary tumor is completely destroyed and only the metastatic tumor is discovered. About 40% of human melanomas contain activating mutations affecting the structure of the B-Raf protein, resulting in constitutive signaling through the Raf to MAP kinase pathway.An insult common to most cancers is damage to DNA. UVA light mainly causes thymine dimers. UVA also produces reactive oxygen species and these inflict other DNA damage, primarily single-strand breaks, oxidized pyrimidines and the oxidized purine 8-oxoguanine (a mutagenic DNA change) at 1/10, 1/10, and 1/3rd the frequencies of UVA-induced thymine dimers, respectively. If unrepaired, CPD photoproducts can lead to mutations by inaccurate translesion synthesis during DNA replication or repair.