What should I look for when I examine my skin for melanoma?

DEAR DOCTOR K:

My aunt developed the skin cancer called melanoma, and I hear that this cancer can run in families. What should I look for when I examine my skin for melanoma?

DEAR READER:

Skin cancers are the most common cancers in the United States, and skin checks are an important way to identify them. You asked about the deadliest type of skin cancer, melanoma.

My Harvard Medical School colleague, dermatologist Dr. Kenneth Arndt, says that more than half of melanomas are identified by patients, either alone or with the help of a partner. That’s important because more than 90 percent of cases can be cured with early detection and treatment.

Skin carries out many functions that help maintain health. It forms a defensive barrier, protecting inner organs from foreign invaders such as bacteria and viruses. It helps control body temperature. Finally, it uses the sun’s energy to make vitamin D, which is essential to many bodily functions.

Skin cancers form in the epidermis, the outermost layer of the skin. Cells called melanocytes, located in the epidermis, produce a dark pigment called melanin. This pigment colors skin and helps protect against the sun’s ultraviolet rays. Melanoma begins in the melanocytes.

Often, these melanocytes are part of a pigmented spot on the skin called a mole (the medical term is “nevus”) that is not cancerous. However, the melanocytes in the nevus can start to turn cancerous. That changes the appearance of the pigmented spot on the skin. Without early detection and treatment, melanoma can spread throughout the body, and sometimes is fatal.

You can help to detect early skin changes by taking a few minutes each month to inspect your skin (or asking your partner to). Melanoma has several distinguishing features. (I’ve put photos illustrating these characteristics, below.)

The best way to check skin: ABCD
Asymmetry. Melanoma is asymmetrical. A
Border irregularity. Melanoma borders are shabby and uneven. B
Color. Melanomas are usually very dark. C
Diameter. Most melanomas are larger than 5 millimeters. D

When you and/or your partner examine your skin, check for the following “ABCDEs.” If you have a pigmented area with any of these characteristics, see a dermatologist.

ASYMMETRY. Each half of the mole looks different than the other.

BORDER IRREGULARITY. The borders are irregular, ragged or blurry.

COLOR. The color is unusual — for example, a mole that contains various shades of tan, brown, blue or black.

DIAMETER. The width of the mole is the size of a pencil eraser or larger.

EVOLVING. The mole has evolved, enlarged or changed in some way.

Sores that crust, bleed and itch are also suspect.

If the doctor suspects melanoma, he or she may take a biopsy. This entails removing part or all of the growth and examining it under a microscope to determine whether it’s cancer.

Sometimes people inherit a vulnerability to developing melanoma; about 10 percent of melanomas have such a genetic basis. If you inherit certain characteristics, you also are at higher risk for melanoma: red or blond hair color, lots of freckles, light eye color (green, hazel, blue), and fair (lightly pigmented) skin. Also very important in raising your risk is frequent and intense exposure to sunlight.