Moles form when skin cells called melanocytes cluster together and are exposed to sunlight, according to How Stuff Works. This sun exposure causes moles to become darker in color, which makes them more noticeable. A natural skin pigmentation called melanin gives moles their unique color.
According to the Mayo Clinic, people can develop anywhere from 10 to 40 moles somewhere on the body during a lifetime. Moles can begin forming in childhood and continue to appear well into middle age. As people age, new moles can form while others completely disappear. The growths are typically round or oval in shape. They come in a variety of colors including brown, tan, pink, blue, red or flesh-colored.
Some moles are easy to spot while others are hidden in discreet places. A mole can grow anywhere on the body including the face, neck, arms, chest, hands and even the scalp. The vast majority of moles are perfectly harmless, although, they may change in shape, color and texture over time.
People that have dysplastic nevi or more than fifty moles are at a greater risk for developing skin cancer, according to Web MD. Cancer forms when abnormal melanoma develops within the mole, and malignant cells replace the normal skin cells. Cancerous moles change in appearance and may bleed, become itchy or painful. Moles that are suspect should be looked at by a dermatologist.