Formation
The natural pigment, called melanin, that gives skin its color is produced in cells. These cells are called melanocytes and form in the top layer of the skin, known as the epidermis, or on the second layer, the dermis. Usually the cells are distributed evenly throughout the skin, but other times the melanocytes grow in clusters, evolving into moles. Scientists don't know why moles are formed or what purpose they serve, says the Mayo Clinic. They will form on the back, arms, legs or face and will last 10 to 40 years before fading away. Moles usually appear in early childhood and during the first 20 years of a person's life. But the moles begin to disappear after that. By the time most people reach age 70 or 80 they have very few moles.
Changes
Moles are usually brown or black. They can appear anywhere on the skin. Moles can change over the years. They can darken after exposure to the sun and during pregnancy. They might also became raised and lighter in color or develop hair. Some moles won't change at all. Although most moles are benign, you might be concerned if there are changes in a mole's color, height, size or shape, the Cleveland Clinic advises. You should also be concerned if the mole bleeds, oozes itches, appears scaly or becomes tender or painful. Any unusual looking moles could indicate skin cancer, so they should be examined by a dermatologist. Moles can also be hereditary. Moles that run in families are often larger than average, about ¼ inch or the diameter of a pencil eraser. They usually have dark brown centers and lighter, uneven borders. Large moles a birth also occur. Unfortunately, both of these types of moles can increase a person's risks of malignant melanoma, the worst and most deadly form of skin cancer. Have your doctor examine these moles on a regular basis.
Sun Effects
Although doctors know little about the origin of moles, they do know that most are benign and some over time can turn out to be cancerous, especially after age 20. Basal cell carcinoma and squamous cell carcinoma are skin cancers that are not as serious as melanoma. They can both can be removed surgically. But they should be treated as soon as possible. Excessive sun exposure is explained for the formation of these skin cancer moles. When genetic material, DNA, is damaged by the sun's ultraviolet light, it changes the formation of the moles. New cells can grow from the mole and form cancer cells, because the sun's ultraviolet radiation penetrates deeply into the skin to cause sunburn and cancers.
