Cells in the skin sometimes change and no longer grow or behave normally. 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. Non-melanoma skin cancer is uncommon but not rare among the Chinese population in Hong Kong. The incidence of newly-diagnosed basal cell carcinoma in 1990 was 16.0 per 10000 new skin case attendances and, in 1999, the incidence was 31.8 per 10000 new skin case attendances. The corresponding figures for squamous cell carcinoma in 1990 and 1999 were 6.9 and 11.6 per 10000 new skin case attendances. The incidence of basal cell carcinoma among the Hong Kong Chinese population in 1990 and 1999 was 0.32 and 0.92 per 100000, respectively
Reducing exposure to UV radiation, particularly by reducing sun exposure, lowers the risk of developing skin cancer significantly. This is important for people of all ages and is especially important for people who have other risk factors for basal cell and squamous cell carcinoma. 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.