Moles (nevi) are a common type of skin growth. They often appear as small, dark brown spots and are caused by clusters of pigment-forming cells (melanocytes). Most people have 10 to 40 moles that appear during childhood and adolescence and may change in appearance or fade over time.
Most moles are harmless. Rarely, they become cancerous. Being aware of changes in your moles and other pigmented patches is important to detecting skin cancer, especially malignant melanoma.
The typical mole is a small brown spot. But moles come in different colors, shapes and sizes:
- Color and texture. Moles can be brown, tan, black, blue, red or pink. They can be smooth, wrinkled, flat or raised. They may have hair growing from them.
- Shape. Most moles are oval or round.
- Size. Moles are usually less than 1/4 inch (about 6 millimeters) in diameter — the size of a pencil eraser. Those present at birth (congenital nevi) can be bigger than usual, covering part of the face, torso or a limb.
Moles can develop anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. Most people have 10 to 40 moles. Many of these develop by age 50. Moles may change or fade away over time. With hormonal changes in adolescence and pregnancy, they may become darker and larger.
Clusters of brown spots around the eyes, cheeks and nose are sometimes called flesh moles, but they are actually dermatoses papulosa nigra — a type of seborrheic keratosis, not clusters of pigment-forming cells (nevi). Dermatoses papulosa nigra are more common among Black women. Flesh moles don't carry a risk of melanoma, but they can be treated if you consider them a cosmetic concern.
Unusual moles that may indicate melanoma
A mole may be a sign of skin cancer if it has irregular borders or an asymmetrical shape or if it changes in color, shape, size or height. This ABCDE guide can help you remember what to watch for:
- A is for asymmetrical shape. One half is unlike the other half.
- B is for border. Look for moles with irregular, notched or scalloped borders.
- C is for color. Look for growths that have changed color, have many colors or have uneven color.
- D is for diameter. Look for new growth in a mole larger than 1/4 inch (about 6 millimeters).
- E is for evolving. Watch for moles that change in size, shape, color or height. Moles may also evolve to develop new signs and symptoms, such as itchiness or bleeding.
Cancerous (malignant) moles vary greatly in appearance. Some may show all of the changes listed above. Others may have only one or two unusual characteristics.
When to see a doctor
Make an appointment with your doctor if a mole looks unusual, grows or otherwise changes.
Moles are caused when cells in the skin called melanocytes grow in clusters. Melanocytes are generally distributed throughout the skin. They produce melanin, the natural pigment that gives skin its color.
Melanoma is the main complication of moles. Some people have higher-than-average risk of their moles becoming cancerous and developing into melanoma. Factors that increase melanoma risk include:
- Being born with large moles. These types of moles are called congenital nevi. On an infant, such moles are classified as large if they're more than 2 inches (5 centimeters) in diameter. Even a large mole seldom becomes cancerous.
- Having unusual moles. Moles that are large and irregular in shape are known as atypical (dysplastic) nevi. They tend to run in families.
- Having many moles. Having more than 50 moles indicates an increased risk of melanoma and possibly breast cancer.
- Having a personal or family history of melanoma. If you've had melanoma before, you are at increased risk of a mole becoming cancerous. In addition, some types of atypical nevi lead to a genetic form of melanoma.
The following measures can help limit the development of moles and the main complication of moles — melanoma.
Watch for changes
Become familiar with the location and pattern of your moles. Regularly examine your skin to look for changes that may signal melanoma. Do self-exams of the skin once a month. With the help of mirrors, do a head-to-toe check, including your scalp, palms and fingernails, armpits, chest, legs, and feet, including the soles and the spaces between the toes. Also check the genital area and between the buttocks.
Talk with your doctor about your risk factors for melanoma and whether you need a professional skin exam on a routine basis.
Protect your skin
Take measures to protect your skin from ultraviolet (UV) radiation, such as from the sun or tanning beds. UV radiation has been linked to increased melanoma risk. And children who haven't been protected from sun exposure tend to develop more moles.
- Avoid peak sun times. For many people in North America, the sun's rays are strongest between 10 a.m. and 4 p.m. Try to schedule outdoor activities for other times of the day, even on cloudy days or in winter. When you are outdoors, seek shade or use a sun-protective umbrella.
- Use sunscreen year-round. Apply sunscreen about 30 minutes before going outdoors, even on cloudy days. Use a sunscreen with an SPF of at least 15. Apply it generously and reapply every two hours — or more often if you're swimming or sweating. The American Academy of Dermatology recommends using a broad-spectrum, water-resistant sunscreen with an SPF of at least 30.
- Cover up. Sunglasses, broad-brimmed hats, long sleeves and other protective clothing can help you avoid damaging UV rays. You might also want to consider clothing that's made with fabric specially treated to block UV radiation.
- Avoid tanning lamps and beds. Tanning lamps and beds emit UV rays and can increase your risk of skin cancer.