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).
Skin cancers involve abnormal cell changes in the outer layer of skin.
It is by far the most common cancer in the world, accounting for 75% of all cancer diagnoses. Most cases are cured, but the disease is a major health concern because it affects so many people. The incidence of skin cancer is rising, even though most cases could be prevented by limiting the skin's exposure to ultraviolet radiation.
Skin cancer is about three times more common in men than in women, and the risk...
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 appear 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).
Primary Medical Reviewer
Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer
Alexander H. Murray, MD, FRCPC - Dermatology
December 17, 2010
WebMD Medical Reference from Healthwise
December 17, 2010
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