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Cancer starts when body cells grow out of control, multiplying and crowding other normal cells. Most skin cancers eventually form a spot or lesion that can sometimes be seen as a spot or unusual mole during an exam.
Non-melanoma skin cancer forms in the lower part of the outer layer of the skin or in basal or squamous cells, but not in the skin cells that make pigment (melanocytes, where melanoma can occur).
Some skin cancers are faster growing than others, and they may grow into nearby tissues or spread (metastasize) to other parts of the body. That’s why it’s important to see a doctor if you notice an unusual spot, even if there aren’t other symptoms.