Skin cancer

DEFINITION

Skin cancer — the abnormal growth of skin cells — most often develops on skin exposed to the sun. But this common form of cancer can also occur on areas of your skin not ordinarily exposed to sunlight.

There are three major types of skin cancer — basal cell carcinoma, squamous cell carcinoma and melanoma.

You can reduce your risk of skin cancer by limiting or avoiding exposure to ultraviolet (UV) radiation. Checking your skin for suspicious changes can help detect skin cancer at its earliest stages. Early detection of skin cancer gives you the greatest chance for successful skin cancer treatment.

CAUSES

Skin cancer occurs when errors (mutations) occur in the DNA of skin cells. The mutations cause the cells to grow out of control and form a mass of cancer cells.

Cells involved in skin cancer

Skin cancer begins in your skin’s top layer — the epidermis. The epidermis is a thin layer that provides a protective cover of skin cells that your body continually sheds. The epidermis contains three main types of cells:

• Squamous cells lie just below the outer surface and function as the skin’s inner lining.
• Basal cells, which produce new skin cells, sit beneath the squamous cells.
• Melanocytes — which produce melanin, the pigment that gives skin its normal color — are located in the lower part of your epidermis. Melanocytes produce more melanin when you’re in the sun to help protect the deeper layers of your skin.

Where your skin cancer begins determines its type and your treatment options.

Ultraviolet light and other potential causes

Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and in the lights used in tanning beds. But sun exposure doesn’t explain skin cancers that develop on skin not ordinarily exposed to sunlight. This indicates that other factors may contribute to your risk of skin cancer, such as being exposed to toxic substances or having a condition that weakens your immune system.

SYMPTOMS

Where skin cancer develops

Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms and hands, and on the legs in women. But it can also form on areas that rarely see the light of day — your palms, beneath your fingernails or toenails, and your genital area.

Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in people with dark skin tones, it’s more likely to occur in areas not normally exposed to the sun, such as the palms of the hands and soles of the feet.

Basal cell carcinoma signs and symptoms

Basal cell carcinoma usually occurs in sun-exposed areas of your body, such as your neck or face.

Basal cell carcinoma may appear as:

• A pearly or waxy bump
• A flat, flesh-colored or brown scar-like lesion

Squamous cell carcinoma signs and symptoms

Most often, squamous cell carcinoma occurs on sun-exposed areas of your body, such as your face, ears and hands. People with darker skin are more likely to develop squamous cell carcinoma on areas that aren’t often exposed to the sun.

Squamous cell carcinoma may appear as:

• A firm, red nodule
• A flat lesion with a scaly, crusted surface

Melanoma signs and symptoms

Melanoma can develop anywhere on your body, in otherwise normal skin or in an existing mole that becomes cancerous. Melanoma most often appears on the face or the trunk of affected men. In women, this type of cancer most often develops on the lower legs. In both men and women, melanoma can occur on skin that hasn’t been exposed to the sun.

Melanoma can affect people of any skin tone. In people with darker skin tones, melanoma tends to occur on the palms or soles, or under the fingernails or toenails.

Melanoma signs include:

• A large brownish spot with darker speckles
• A mole that changes in color, size or feel or that bleeds
• A small lesion with an irregular border and portions that appear red, white, blue or blue-black
• Dark lesions on your palms, soles, fingertips or toes, or on mucous membranes lining your mouth, nose, vagina or anus

Signs and symptoms of less common skin cancers

Other, less common types of skin cancer include:

• Kaposi sarcoma. This rare form of skin cancer develops in the skin’s blood vessels and causes red or purple patches on the skin or mucous membranes.

  Kaposi sarcoma mainly occurs in people with weakened immune systems, such as people with AIDS, and in people taking medications that suppress their natural immunity, such as people who’ve undergone organ transplants.

  Other people with an increased risk of Kaposi sarcoma include young men living in Africa or older men of Italian or Eastern European Jewish heritage.

• Merkel cell carcinoma. Merkel cell carcinoma causes firm, shiny nodules that occur on or just beneath the skin and in hair follicles. Merkel cell carcinoma is most often found on the head, neck and trunk.
• Sebaceous gland carcinoma. This uncommon and aggressive cancer originates in the oil glands in the skin. Sebaceous gland carcinomas — which usually appear as hard, painless nodules — can develop anywhere, but most occur on the eyelid, where they’re frequently mistaken for other eyelid problems.

When to see a doctor

Make an appointment with your doctor if you notice any changes to your skin that worry you. Not all skin changes are caused by skin cancer. Your doctor will investigate your skin changes to determine a cause.