skin cancer is the most commonly diagnosed type of cancer. melanoma and non-melanoma skin cancers combined are more common than lung, breast, colorectal, and prostate cancer. melanoma is less common than both basal cell carcinoma and squamous cell carcinoma, but it is the most serious — for example, in the uk there were over 11,700 new cases of melanoma in 2008, and over 2,000 deaths. it is the second most common cancer in young adults aged 15–34 in the uk. most cases are caused by over-exposure to uv rays from the sun or sunbeds.