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Risk Factors for Melanoma And Squamous Cell Cancer

Other Risk Factors for Melanoma The following risk factors increase the risk of melanoma:

• Dysplastic nevus: A dysplastic nevus is a type of mole that looks different from a common mole. A dysplastic nevus may be bigger than a common mole, and its color, surface, and border may be different. It’s usually wider than a pea and may be longer than a peanut. A dysplastic nevus can have a mixture of several colors, from pink to dark brown. Usually, it’s flat with a smooth, slightly scaly or pebbly surface, and it has an irregular edge that may fade into the surrounding skin. A dysplastic nevus is more likely than a common mole to turn into cancer. However, most do not change into melanoma. A doctor will remove a dysplastic nevus if it looks like it might have changed into melanoma.

• More than 50 common moles: Usually, a common mole is smaller than a pea, has an even color (pink, tan, or brown), and is round or oval with a smooth surface. Having many common moles increases the risk of developing melanoma.

Other Risk Factors for Both Basal Cell and Squamous Cell Skin Cancers The following risk factors increase the risk of basal cell and squamous cell skin cancers:
• Old scars, burns, ulcers, or areas of inflammation on the skin
• Exposure to arsenic at work
• Radiation therapy

Other Risk Factors for Squamous Cell Cancer

The risk of squamous cell skin cancer is increased by the following:
• Actinic keratosis: Actinic keratosis is a type of flat, scaly growth on the skin. It is most often found on areas exposed to the sun, especially the face and the backs of the hands. The growth may appear as a rough red or brown patch on the skin. It may also appear as cracking or peeling of the lower lip that does not heal. Without treatment, this scaly growth may turn into squamous cell skin cancer.

• HPV (human papillomavirus): Certain types of HPV can infect the skin and may increase the risk of squamous cell skin cancer. These HPVs are different from the HPV types that cause cervical cancer and other cancers in the female and male genital areas.

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Skin cancers are named for the type of cells that become malignant (cancer). The three most common

types are:

• Melanoma: Melanoma begins in melanocytes (pigment cells). Most melanocytes are in the skin. See the picture on page 4 of a melanocyte and other skin cells. Melanoma can occur on any skin surface. In men, it’s often found on the skin on the head, on the neck, or between the shoulders and the hips. In women, it’s often found on the skin on the lower legs or between the shoulders and the hips. Melanoma is rare in people with dark skin. When it does develop in people with dark skin, it’s usually found under the fingernails, under the toenails, on the palms of the hands, or on the soles of the feet.

• Basal cell skin cancer: Basal cell skin cancer begins in the basal cell layer of the skin. It usually occurs in places that have been in the sun. For example, the face is the most common place to find basal cell skin cancer. In people with fair skin, basal cell skin cancer is the most common type of skin cancer.

• Squamous cell skin cancer: Squamous cell skin cancer begins in squamous cells. In people with dark skin, squamous cell skin cancer is the most common type of skin cancer, and it’s usually found in places that are not in the sun, such as the legs or feet.  However, in people with fair skin, squamous cell skin cancer usually occurs on parts of the skin that have been in the sun, such as the head, face, ears, and neck.

Unlike moles, skin cancer can invade the normal tissue nearby. Also, skin cancer can spread throughout the body. Melanoma is more likely than other skin cancers to spread to other parts of the body. Squamous cell skin cancer sometimes spreads to other parts of the body, but basal cell skin cancer rarely does. When skin cancer cells do spread, they break away from the original growth and enter blood vessels or lymph vessels. The cancer cells may be found in nearby lymph nodes. The cancer cells can also spread to other tissues and attach there to form new tumors that may damage those tissues. The spread of cancer is called metastasis. See the Staging section on page 17 for information about skin cancer that has spread.