Shallow of carcinoma ulcer the skin pigment melanin. The risk is reduced by avoiding overexposure to strong sunlight, using sunscreens, and wearing protective clothing and sun hats. Without treatment, the carcinoma gradually invades and destroys surrounding tissues but virtually never spreads to other parts of the body. Treatment is usually with surgery (or in some cases radiotherapy) and is often completely successful. Plastic surgery may also be needed, however, depending on the size and site of the tumour. People who have had a basal cell carcinoma may develop new tumours and should be alert to any changes in their skin. (See also melanoma, malignant; squamous cell carcinoma; sunlight, adverse effects of.)