Dysplastic nevi, also known as atypical moles, are unusual benign moles that may resemble melanoma. People who have them are at an increased risk of melanoma. The larger the number of atypical moles, the greater the risk. Individuals with 10 or more of them have 12 times the risk of developing melanoma as members of the general public.
Heredity plays a part, and people with a family history of melanoma (two or more close blood relatives) as well as atypical moles are at the highest risk. However, those with atypical moles and no family history still have a 7 to 27 times higher risk than the general public.
The classic atypical mole syndrome has the following characteristics:
- 100 or more moles
- One or more moles greater than 8mm (1/3 inch) or larger in diameter
- One or more moles that look atypical
Normal Moles vs. Dysplastic Nevi
The average young adult has about 10-20 normal moles or growths. Generally, normal moles have the following characteristics:
- Shape: symmetrical, round, or oval
- Border: regular, sharp, and well-defined
- Color: usually tan, brown, or skin color
- Diameter: usually 6 mm (1/4 inch) or smaller — about the size of a pencil eraser
- Location: often concentrated on sun-exposed areas, such as the face, trunk, arms and legs.
- Onset: early childhood through age 40
- Uniformity: resemble one another
Even normal moles increase the likelihood of malignancy, provided they are numerous. The greater the total number of moles on the body, the greater the overall danger of melanoma.
Dysplastic Nevi vs. Melanoma
It is sometimes difficult to tell the difference between dysplastic nevi and melanoma. A mole that appears suspicious–changes in size, shape or color–or if a new mole appears after 40, the doctor will remove the entire mole or a part of it for microscopic examination. Sometimes a melanoma begins within a dysplastic nevus.
Sometimes, melanomas will begin within the mole itself. Dysplastic nevi usually have the following characteristics:
- Shape: asymmetrical; a line drawn through the middle would not create matching halves
- Border: irregular or poorly defined
- Color: variation with shades of tan, brown, dark brown, or black, or mixed
- Diameter: generally but not always larger than 6 mm
- Location: most commonly on the back, chest, abdomen, extremities and scalp; may also occur on normally unexposed areas such as buttocks, groin or female breasts
- Growth: enlargement of a previously stable mole or appearance of a new mole after age 40 should raise suspicion
- Surface: central portion is flat to slightly raised
- Appearance: greatly varied; dysplastic nevi often look different from one another
- Number: from a few to well over 100
More Serious Warning Signs
Some dysplastic nevi display more serious warning signs of melanoma: itching, elevation, crusting, oozing, a bluish-black color, pain, bleeding, swelling and ulceration. If any of these warning signs appear on your own skin or that of a friend or family member, consult a dermatologist right away. It could be the first sign of skin cancer.