Dysplastic nevi are benign moles that can have an appearance similar to that of cancerous skin growths. These moles may have an irregular border, an asymmetrical appearance, an irregular color or all three. Dysplastic nevi are noncancerous, but malignant skin cancers can occasionally begin within such a mole. The presence of dysplastic moles is one of the risk factors for developing the malignant skin cancer melanoma.
Dysplastic nevi are generally more than 0.25 of an inch (6 mm) in diameter. They are most common on the back, abdomen, chest, arms and legs, but can also occur in places not normally exposed to the sun, such as the buttocks, scalp, groin and breasts. They are often asymmetric in shape and can be multicolored — tan, brown, black, red and even blue. The border of a dysplastic nevus is irregular and sometimes fades into the skin around it. The surface of the mole can be raised in the center or have a pebbled texture.
Most people have normal moles, usually between 10 and 40. New normal moles can develop at any time up to the age of 40. Normal moles are generally smaller than dysplastic nevi and more regular in shape, color and texture. They are not a significant risk factor for skin cancer, unless they are present in quantities of 100 or more along with at least one dysplastic nevus.
Dysplastic nevi can appear similar to melanoma growths, so a doctor may have to biopsy a suspicious nevus to rule out cancer. This will involve cutting out all or part of the mole for analysis. Generally, only a dysplastic nevus that has appeared after the age of 40 or a mole with an appearance that has changed is tested. Appearance changes that could indicate the presence of skin cancer include a change in shape, color or size. Other indications that the mole could have turned cancerous are if the mole starts bleeding or itching.
A dysplastic nevus is in itself not dangerous and, according to the U.S Skin Cancer Foundation, up to 8 percent of Caucasians have at least one. People who are at higher risk than the general public of developing melanoma should ensure they regularly check their body for changes in the appearance of any moles or the development of new dysplastic nevi. High-risk factors include having light hair or eyes, more than 100 normal moles and at least one dysplastic mole, freckles, a family history of melanoma, repeated and intermittent sunburns, a large mole at birth or an inability to tan.