Cancer that begins in the lower part of the epidermis (the outer layer of the skin). It may appear as a small white or flesh-colored bump that grows slowly and may bleed. Basal cell cancers are usually found on areas of the body exposed to the sun. Basal cell cancers rarely metastasize (spread) to other parts of the body. They are the most common form of skin cancer. Also called basal cell carcinoma.