Moles

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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 sizes and colors. They 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 mid-adulthood, and because moles last about 50 years, some moles may disappear as you age.

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.

What do they look like?

The typical mole is a plain, brown spot. Moles come in a wide variety of colors, shapes and sizes.

  • Color: Moles 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.
  • 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.

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.

Are moles (Nevi) something to be concerned about?

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.

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