Dysplastic nevi, also known as atypical moles, are moles that may have an irregular appearance and or atypical cells when examined under the microscope. People who have them are at an increased risk of melanoma. The larger the number of atypical moles, the greater the risk.

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

Persons with numerous moles, even if they are normal, are at increased risk of melanoma. The risk increases notably in persons who have also used indoor tanning beds.

Dysplastic Nevi Vs. Melanoma

It is sometimes difficult to tell visually the difference between a dysplastic nevus and melanoma. It is recommended to evaluate a mole for a biopsy if the following occurs: 1) any mole that appears suspicious, for example it changes in size, shape or color, or 2) if a new mole appears after the age of 40. Depending on the findings, your dermatologist may want to further remove an atypical/dysplastic mole. We don't know that an atypical mole will turn into melanoma; however, we do know that melanoma can develop within an atypical mole.

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.