The ABCDE Rule of Skin Cancer

Checking your skin for suspicious changes can help identify potential malignancies in their earliest stages. This, in turn, can increase your chance for successful treatment.

The ABCDE Rule of skin cancer is not meant to be tool for diagnosis but rather one by which individuals and doctors can differentiate between a problem growth and a simple, everyday blemish.


The ABCDE Rule is broken down as follows:

A for Asymmetry

Normal moles or freckles are typically symmetrical. If you were to draw a line through the center, you would have two symmetrical halves. In cases of skin cancer, spots will not look the same on both sides. (Shape alone doesn’t suggest a malignancy, since some birthmarks will irregular in shape, but is certainly one of the features doctors look for when identifying skin cancers.)


B for Border

Moles, spots, or “beauty marks” are typically round and of no cause for concern. Ones a with blurry and/or jagged edge can be a sign of a cancerous or pre-cancerous growth.


C for Color

Change in color should be considered suspicious. Normal mole and spots, by contrast, are usually one color. Color changes can include the darkening of a spot (sometimes to dark purple to black) or a lightening in certain parts of the growth.


D for Diameter

If a growth is larger than a pencil eraser (about 1/4 inch or 6mm), it needs to be checked by a doctor. This includes areas of skin that do not have any other abnormalities in terms of color, border, or asymmetry. This is not to suggest that smaller growths don’t warrant investigation — including skin tags, but those over 1/4 inches will always be of particular concern.


E for Evolution

History of change in the lesion.


When to See a Doctor:

If you notice any changes to your skin that worry you, don’t hesitate. See your doctor or ask for a referral to a quailified dermatologist. This is particularly true if there is any blemish or growth that changes rapidly or bleeds easily. While not all skin changes are caused by cancer, the advantages of early diagnosis greatly outweighs the inconvenience (and even cost) of a doctor’s visit.


Reference: Diepgen, T. and Mahler, V. “The Epidemiology of Skin Cancer.” British Journal of Epidemiology. April 2002; 146:1-6.

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