Cells in the skin sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous, or benign, tumours such as dermatofibromas, epidermal cysts or moles (also called nevi).Changes to cells in the skin can also cause cancer. Different types of skin cells cause different types of skin cancers. When skin cancer starts in squamous cells or basal cells, it is called non-melanoma skin cancer. When cancer starts in melanocytes, it is called melanoma. The commonest type of NMSC is basal cell carcinoma. In Trentino, Italy, the Skin Cancer Registry calculated (for the period 1993–1998) that the incidence rate of BCC was 88 per 100,000, of SCC it was 29 per 100,000 and it was 14 per 100,000 for melanoma. SCC was equally common in men and women, BCC were nearly three times more frequent in men.
It is estimated that basal cell carcinoma will spread to other parts of the body in less than 0.5% of cases. The risk is slightly higher in cases of squamous cell carcinoma, which spreads to other parts of the body in around 2-5% of cases.Many clinical trials are focused on new treatments, evaluating whether a new treatment is safe, effective, and possibly better than the current treatment. These types of studies evaluate new drugs, different combinations of existing treatments, new approaches to radiation therapy or surgery, and new methods of treatment.