To find out whether it is a mole or cancer, check your skin every few months, because most skin cancers start as irregular spots, says Ariel Ostad, MD, assistant professor of dermatology at New York University.
Normal mole
What it is: A mole is a harmless spot that develops in childhood or later in life and can be found anywhere.
Looks Like: Typically smaller than a pencil eraser, moles are round and symmetrical with smooth borders and an even color. According to Dr. Ostad, “They usually don’t evolve or change shape.”
Actinic keratosis
What it is: Actinic keratosis is a common precancerous growth often found on your scalp, face, hands, or forearms. “They should be removed because 5 to 10 percent of them become cancerous,” Dr. Ostad explains.
Looks Like: You’ll see a rough, flesh-toned pink or red patch that may be itchy or scaly.
Basal cell carcinoma
What it is: Caused by sun damage and typically found on the face, this type of cancer is easy to treat if it’s caught early.
Looks Like: It normally appears as a pinkish or reddish patch that may bleed or scab. “Picture a pimple that seems to heal, only to return again,” Dr. Ostad says.
Squamous cell carcinoma
What it is: This type of cancer often appears on the body, legs, or hands and is curable if caught early.
Looks Like: You’ll notice a thick growth that can peel and bleed and may have an irregularly shaped border. “It’s more like a wart than a pimple,” Dr. Ostad says.
Melanoma
What it is: This serious form of cancer can spread quickly but is curable if caught early. “Melanoma is usually found on women’s legs, rarely on their faces,” Dr. Ostad says. “In men, it’s more common on the torso.”
Looks Like: Alert your derm if you see a dark, irregularly shaped growth with uneven reddish-brown, brown, or black coloring.
source: http://www.health.com/health/gallery/thumbnails/0,,20307251,00.html