The main signs of skin cancer are spots on the skin that change shape, color or size and newly developed spots, according to the American Cancer Society. Spots on the skin that look different from other areas of the skin may also indicate skin cancer.
Additional warning signs of skin cancer include redness or swelling beyond the border of the skin, changes in the surface of a mole, such as in the form of bleeding, oozing or scaliness, and changes in skin sensation, such as pain, tenderness or itchiness, explains the American Cancer Society. A sore that does not heal and the spread of pigment from the border of a sore or spot into the surrounding skin should also cause concern.
Most physicians recommend the ABCDE guide to spotting the signs of skin cancer, according to the American Cancer Society. Patients should check for asymmetry and inspect the borders of skin spots. For example, the warning signs for skin cancer include borders and edges of a spot that are ragged, notched or blurred as well as one half of a birthmark or mole that does not match another. If a spot differs in color or the diameter of the spot is larger than one-fourth inch across, it could signify skin cancer. Overall, physicians recommend observing how spots evolve on the skin, such as through changes in shape, size and color of moles or skin spots.