Mole also known as a melanocytic, melanotic or pigmented naevus on a woman's shoulder. It is caused by an abnormality or overactivity of the melanocytes, the skin cells that produce the pigment melanin. Moles vary considerably in size and appearance. They are unusual at birth and tend to appear in childhood and adolescence, averaging between 15-20 in number in adulthood. Most moles are harmless, but they may turn cancerous, which could be indicated by a change in colour, size or becoming itchy.