Basal cell cancer begins in the lowest layer of the epidermis, the basal cell layer. About 8 out of 10 skin cancers are basal cell carcinomas. They usually begin on areas exposed to the sun, such as the head and neck. Basal cell carcinoma was once found mostly in middle-aged or older people. But now it is also being seen in younger people. This may be because people are spending more time in the sun without protecting their skin.
Basal cell carcinoma tends to grow slowly. It is very rare for a basal cell cancer to spread to distant parts of the body (metastasize). But if it is not treated, it can grow into nearby areas and spread into the bone or other tissues beneath the skin.
After treatment, basal cell carcinoma can come back (recur) in the same place on the skin. New basal cell cancers can also start in other places on the skin. As many as half of the people who have one basal cell cancer will get a new skin cancer within 5 years.