The skin cells that produce pigment (melanocytes) sometimes group together to form
moles. Most people have at least 10 moles on their
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
melanoma. 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
ABCDE rule of detection means watching for:
- Asymmetry . One half
doesn't match the other half.
- Border irregularity . The
edges are ragged, notched, or blurred.
- Color . 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.
- Diameter . 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.
- Evolution . 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.
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
- Giant congenital melanocytic nevus (giant hairy
nevus or garment nevus).
- Small to medium-sized congenital
- Some heavily pigmented lesions of the membrane
that line the eyelids (conjunctiva).
Kathleen Romito, MD - Family Medicine
Amy McMichael, MD - Dermatology
October 12, 2012