Basal cell carcinoma is a cancer of the cells at the bottom of the skin’s outermost layer, the epidermis. It accounts for more than three-quarters of all skin cancers in the UK. Most basal cell carcinomas are slow-growing and almost never spread. However, if they are left untreated they can erode the skin and cause an ulcer, known as a rodent ulcer. A small number of rodent ulcers come back on the same area of skin after treatment: this is known as a local recurrence.

Squamous cell carcinoma is a cancer of the outermost cells of the skin. It is the second most common type of skin cancer in the UK. One in five skin cancers (20%) are this type. If it is left untreated for a long time, squamous cell carcinoma can spread to other parts of the body. However, most people treated for squamous cell carcinoma are completely cured with simple treatment.

Another, much less common, type of skin cancer is called malignant melanoma. About 7,000 people in the UK are diagnosed with malignant melanoma each year. Melanoma behaves differently to basal cell and squamous cell carcinomas.