Skin cancer or mole? How to tell

One in five Americans will develop skin cancer, making it the most common form of cancer in the U.S., according to the Skin Cancer Foundation. But you can protect yourself by regularly checking your skin. In the slides that follow, Dr. Ariel Ostad, a dermatologic surgeon in New York City, explains how to tell benign moles and birthmarks from deadly cancers. But always check with your own doctor.

Here is a picture of lips with actinic keratoses, a common precancer.

Melanoma

Not every skin cancer is as obvious as this one. Most get their start as small, seemingly harmless "birthmarks" or rough patches. That's why it's vital to examine your skin - doctors recommend a head-to-toe self-exam once a month, says Dr. Ariel Ostad, a dermatologic surgeon in New York City. See something suspicious? See a doctor. In fact, it's smart to discuss skin cancer prevention with your doctor no matter what your skin exams turn up.

Actinic keratosis

Have any red, scaly lesions that look like this? These are actinic keratoses. They aren't cancerous yet, but they can turn cancerous. They should be removed by a doctor.

Actinic keratosis and sun exposure

Actinic keratoses, like those shown here, are the result of accumulated sun damage. They tend to show up on the face, lips, forehead, etc. - anyplace that gets lots of sun exposure.

Persistent pimple? Could be basal cell carcinoma

T here's nothing unusual about having a pimple. But a "pimple" that persists for weeks or months might actually be a form of skin cancer known as basal cell carcinoma. It's the most common form of skin cancer - and the easiest to treat.

Basal cell carcinoma on the nose

Some basal cell carcinomas, like this one, don't look like much - but that doesn't mean it's safe to ignore them, especially if they persist for weeks or longer.

Basal cell carcinoma on the ear

As with actinic keratoses, basal cell carcinomas tend to form on areas of the body that get lots of sun exposure, including the ears. Some bleed, only to heal and bleed again. Left untreated, they can grow, penetrating the skin and muscle and sometimes blood vessels. But unlike more serious forms of skin cancer, they don't spread to other organs.

Squamous cell carcinoma

This is an example of squamous cell carcinoma, the second most common form of skin cancer. Like actinic keratoses, squamous cell carcinomas often start as roughly, scaly patches or bumps - but tend to be thicker and wider than keratoses.

Squamous cell carcinoma on the ear

Like other forms of skin cancer, squamous cell carcinomas tend to form on areas of skin that get lots of sun exposure.

Squamous cell carcinoma

Squamous cell carcinoma can even affect the nails. This is a very advanced case.

Identifying moles

Moles tend to be round or oval, and generally symmetrical - meaning one half looks like the other. Moles are benign and require no treatment.

Moles have well-defined borders

Moles tend to be of one color only and to have well-defined borders.

Change is bad

Moles tend to stay the same. Any mark that gets thicker or wider or changes in any way is cause for concern - and cause for a trip to the doctor. The photo on the right shows a man whose moles have grown in size.

Basal cell carcinomas can fool you

This might look like a mole, but note the asymmetrical shape and varied coloration. It's actually a basal cell carcinoma.

Dysplastic nevus

This isn't a mole but a precancerous lesion called a dysplastic nevus. You can tell because it has poorly defined edges and because it's asymmetrical. Dysplastic nevi can turn into melanoma, the most deadly form of skin cancer. That's why they should be removed as soon as possible.

Dysplastic nevus: look for colors

Another thing that helps distinguish a benign mole from a dysplastic nevus is color. Moles tend to have a uniform color. Dysplastic nevi, like this one shown here, often have areas of different colors - variegated color, as doctors put it.

Dysplastic nevus on the scalp

Dysplastic nevi can occur on the scalp as well as on other parts of the body, especially those that get lots of sun exposure.

Melanoma: the deadliest skin cancer

This is a malignant melanoma, the most severe form of skin cancer. Melanomas - which arise from dysplastic nevi - tend to be assymetrical, with poorly defined borders and often with varied coloration.

Spotting a melanoma

This melanoma exhibits the classic signs: asymmetry, poorly defined edges, and varied coloration.

Melanomas thicken over time

Melanomas often start out flat but thicken over time. The thicker, the deadlier. Melanomas less than 0.75 mm in diameter have a 94 percent cure rate. But when a melanoma is 4 mm or larger, like this one, only one in three patients survive.

Melanoma: Men vs. women

As with other forms of skin cancer, melanomas tend to form in areas of the body that gets lots of skin exposure. In women, melanomas often form on the legs. In men, the back seems to be particularly vulnerable.

Melanoma under the fingernail

Sometimes melanomas form under a fingernail or toenail. In dark-skinned people, including Blacks, Latinos, and Asians, common melanoma sites include the hands, feet and nails.

Advanced melanomas are deadly

This melanoma proved deadly - the patient waited so long to see a doctor that effective treatment was impossible. If you are concerned about your skin, see a doctor. Don't wait.

Skin cancer self-fefense

What else can you do to protect yourself against skin cancer? While outdoors, wear protective clothing (long pants, long sleeves, a hat), says New York dermatologic surgeon Dr. Ariel Ostad. Slather on sunscreen with an SPF of at least 30 - something with "broad-spectrum" protection against ultraviolet A and ultraviolet B rays.