Atypical Moles

The skin cells that produce pigment (Reference melanocytes Opens New Window) sometimes group together to form Reference moles Opens New Window. Most people have at least 10 moles on their bodies.

Melanocytes can form abnormal moles, also called atypical moles or dysplastic nevi. These moles are not malignant themselves. But their presence is a warning of an inherited tendency to develop Reference melanoma Opens New Window. Some people have only 1 or 2 atypical moles. Some people may have more than 100. The tendency to develop atypical moles can run in families (inherited predisposition).

Early signs of melanoma in atypical moles

The Reference ABCDE rule Opens New Window Reference Opens New Window of detection means watching for:

• Reference Asymmetry Opens New Window Reference Opens New Window. One half doesn't match the other half.
• Reference Border irregularity Opens New Window Reference Opens New Window. The edges are ragged, notched, or blurred.
• Reference Color Opens New Window Reference Opens New Window. The pigmentation is not uniform. Shades of tan, brown, and black are present. Dashes of red, white, and blue add to the mottled appearance. Changes in color distribution, especially the spread of color from the edge of a mole into the surrounding skin, also are an indicator of early melanoma.
• Reference Diameter Opens New Window Reference Opens New Window. The size of the mole is larger than 1/4 inch (6 mm), or about the size of a pencil eraser. Any growth of a mole should be of concern.
• Reference Evolution Opens New Window Reference Opens New Window. There is a change in the size, shape, symptoms (such as itching or tenderness), surface (especially bleeding), or color of a mole.

Atypical moles are seen most commonly on the back but may be anywhere on the body, including below the waist, on the scalp, or on the breasts or buttocks. They may fade into surrounding skin and include a flat portion that is level with the skin surface. They may be smooth, slightly scaly, or have a rough, irregular, "pebbly" appearance.

Atypical moles usually are not present at birth but develop some time later.

Several types of atypical moles are known to develop before melanoma (melanoma precursors). Atypical moles are the most common precursor, but not all atypical moles develop into melanoma. Precursors to melanoma include:

• Giant congenital melanocytic nevus (giant hairy nevus or garment nevus).
• Small to medium-sized congenital melanocytic nevus.
• Some heavily pigmented lesions of the membrane that line the eyelids (conjunctiva).

© 1995-2011, Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Reference Terms of Use. Reference How this information was developed to help you make better health decisions.