Cancerous moles are asymmetrical and larger than other moles. They are more than one color and sometimes bleed or ooze, according to the American Academy of Dermatology. The mole may also be scaly and itch; sometimes a new mole that looks normal is the beginning of skin cancer, more specifically melanoma.
The cancerous mole also has an irregular border, explains the American Academy of Dermatology. It changes in size, shape or color or all three over time. Melanoma is the most dangerous type of skin cancer, notes to the Skin Cancer Foundation. In melanoma, the cancer arises from melanocytes, which contain pigments that give color to the moles and the skin. The melanocytes are found in the lowest level of the epidermis, which is the top layer of skin.
Like most skin cancers, melanoma is curable if it is found and treated in its early stages, says the Skin Cancer Foundation. If it is not treated, melanoma can spread very quickly and metastasize to distant sites in the body. By then, it is very difficult to treat and can be life-threatening. Over 135,000 cases of melanoma are diagnosed in the United States every year, and as of 2015, close to 74,000 of those cases are invasive.