Moles

What are they?
Moles, known medically as nevi, are clusters of pigmented cells that often appear as small, dark brown spots. However, moles can come in a range of colors and can develop virtually anywhere on your body.

Most moles are harmless, but in rare cases, moles may become cancerous. Monitoring moles and other pigmented patches is an important step in detecting skin cancer, especially malignant melanoma. Not all melanomas develop from pre-existing moles, but many begin in or near a mole or other dark spot on the skin.

Although the typical mole is a plain, brown spot, moles come in a wide variety of colors, shapes and sizes:

Color. They can be flesh-colored, reddish-brown, medium to dark brown, or blue.

Shape. They can vary in shape from oval to round.

Size. They can be as small as a pinhead or large enough to cover an entire limb. Generally, moles are less than one-quarter of an inch large.

Moles can develop virtually anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. Most people have between 10 and 40 moles, although the number you have may change throughout life. New moles can appear into midadulthood, and because moles last about 50 years, some moles may disappear as you age.

Varied surfaces
The surface of a mole can be smooth or wrinkled, flat or raised. Sometimes a mole may start out flat and brown and later become slightly raised and lighter in color. Some may become raised enough that they form a small stalk and are eventually rubbed off. Others may simply disappear.

Although most moles develop by age 20, they can continue to appear until midlife. There are also certain times in your life when moles are more apt to change; for example, they're likely to become darker, larger and more numerous because of hormonal changes that occur during adolescence or pregnancy.

What causes moles?
Melanin is a natural pigment that gives your skin its color. It's produced in cells called melanocytes, either in the top layer of the skin (epidermis) or the outer layers of the skin's second layer (dermis). Melanin is then transported to the surface cells of your skin. Normally, melanin is distributed evenly, but sometimes melanocytes grow together in a cluster, giving rise to moles.

Scientists don't know why moles develop or what purpose they serve, if any, although they do appear to be determined before birth. Most moles are harmless and don't require special care, but some people have unusual-looking moles, called dysplastic nevi, which are more likely to turn cancerous than ordinary moles are.

What are the your risk factors?
Several types of moles have a higher than average risk of becoming cancerous.

• Large moles present at birth
  Large moles that are present at birth are called congenital nevi or giant hairy nevi. These moles may increase your risk of malignant melanoma, a deadly form of skin cancer. In general, moles that are more than the size of a closed fist pose the greatest risk. Have your doctor examine any mole that was present at birth and is fist-sized or larger.
• Moles that run in families
  Moles that are larger than average - which is about 1/4 inch (6 millimeters), or the diameter of a pencil eraser - and irregular in shape are known as atypical (dysplastic) nevi. These moles tend to be hereditary. They're frequently described as looking like fried eggs because they usually have dark brown centers and lighter, uneven borders. Overall, they may look red or tan. If you have dysplastic nevi, you have a greater risk of developing malignant melanoma.
• Numerous moles
  If you have many moles - 50 or more - you are at a greater risk of developing melanoma.

When to call us:

If you're over 20 years old and a new mole appears

If the mole is painful

If the mole itches or burns

If there is oozing or bleeding

If the mole is scaly or crusty

If the mole is suddenly different in size, shape, color or elevation