A nevus is a benign (non-cancerous) melanocytic tumor, more commonly called a mole. Nevi (the plural of nevus) are not usually present at birth but begin to appear in children and teenagers. Most moles will never cause any problems, but a person who has more than 50 normal moles (or more than 5 atypical or "dysplastic" moles) has a higher risk of developing melanoma, the most aggressive form of skin cancer.
This gallery of photographs will alternate between normal, benign moles and melanoma so that you can learn to recognize each. Important note: Telling moles and melanoma apart is not easy, even for dermatologists with years of training, so be sure to contact your doctor if you have any questions.
This picture of a melanoma skin cancer tumor shows how they are often irregularly shaped and multicolored.
The earlier melanoma is detected, the better the chance for successful treatment. Monthly self-examinations may help find it early. Often, the first sign of melanoma is a change in the size, shape, or color of an existing mole. It also may appear as a new or abnormal-looking mole. The "ABCDE" rule can be used to help remember what to watch for.
This is an example of a normal mole; note that it is almost perfectly round. Melanoma tumors differ in that they are usually asymmetrical (lopsided).
Although most moles are benign (not cancerous), certain types carry a higher risk of developing melanoma. About 2% to 8% of the U.S. Caucasian population has moles called "dysplastic" or "atypical" nevi, which are larger than ordinary moles (most are 5 mm across or larger), have irregular borders, and are various shades or colors. Individuals who have dysplastic nevi plus a family history of melanoma (a syndrome known as FAMM) are at an even higher risk for developing melanoma at an early age (younger than 40).
An example of how melanoma tumors are often asymmetrical (lopsided), unlike non-cancerous moles.
If you have 50 or more normal moles (or 5 or more "dysplastic" moles), you should check your skin thoroughly several times per year. (Even if you don't have any moles, you should do a skin self-exam once per year.) If you see any of the following signs, contact your doctor:
- A new, possibly large, irregularly shaped, dark brownish spot with darker or black areas.
- A simple mole that changes in color (particularly turning darker), size (growing), or texture (becoming firmer), and/or flakes or bleeds.
- A suspicious change in an existing mole or spot.
- A lesion with an irregular border and red, white, blue, gray, or bluish-black areas or spots.
- Dark lesions under the fingernails or toenails, on the palms, soles, tips of fingers and toes, or on mucous membranes (the skin that lines the mouth, nose, vagina, and anus).
A normal mole is shown in this picture. Note that the color is the same throughout the mole -- there are no multiple shades of brown, black, or tan, as is usually seen in melanoma.
This melanoma tumor has a border that is uneven, ragged, or notched. This is another way to distinguish melanoma from normal moles, which typically have borders that are smooth.
Normal moles come in a variety of sizes and colors: (a) a small freckle-like skin discoloration (called a "macule"); (b) a larger macule; (c) a mole that is raised above level of the skin; and (d) a mole that has lost its dark color. None of these examples are melanoma.
A melanoma lesion containing different shades of brown, black, and tan.
The "ABCDE" rule can be used to help you remember what a melanoma tumor typically looks like:
- Asymmetry: The shape of one half of the mole does not match the other.
- Border: The edges are ragged, notched, or blurred.
- Color: The color is often uneven. Shades of black, brown, and tan may be present. Areas of white, gray, red, or blue may also be seen.
- Diameter: The diameter is usually larger than six millimeters (the size of a pencil eraser) or has grown in size. However, melanoma can come in any size.
- Evolving: The mole has been changing in size, shape, color, appearance, or growing in an area of previously normal skin. Also, when melanoma develops in an existing mole, the texture of the mole may change and become hard, lumpy, or scaly. Although the skin may feel different and may itch, ooze, or bleed, melanoma usually does not cause pain.
If you see any of these happening to one of your moles, contact your doctor promptly.
More examples of ordinary moles: (a) a uniformly tan or brown skin discoloration, 1 to 2 mm in diameter, (b) a larger skin discoloration, (c) a mole that is slightly raised above the surface of the skin, (d) a mole that is more clearly raised above the skin, and (e) a pink or flesh-colored mole.
All of these are normal, and even a single mole may go through these stages over time. However, all of them have a smooth border and are clearly separated from the surrounding skin, in contrast to a melanoma tumor.
Our final photograph is a melanoma tumor that is large and had gotten bigger over time -- a key characteristic of a melanoma tumor. If you see any suspicious skin lesion, especially one that is new or changed in size, contact your doctor.
Remember, melanoma can be cured if detected early, unlike many cancers. So knowing your risk factors and communicating them to your doctor may help you make more informed lifestyle and healthcare choices. If you have multiple moles or other risk factors, it is important that you perform regular self examinations of your skin, see a dermatologist for regular examinations, and protect yourself from the sun.