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, the spaces between your toes or under your toenails, and your genital area.
Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in those with dark skin tones, it's more likely to occur in areas not normally considered to be sun-exposed.
A cancerous skin lesion can appear suddenly or develop slowly. Its appearance depends on the type of cancer.
Basal cell carcinoma
This is the most common skin cancer. It's also the most easily treated and the least likely to spread. Basal cell carcinoma usually appears as one of the following:
• A pearly or waxy bump on your face, ears or neck
• A flat, flesh-colored or brown scar-like lesion on your chest or back
Squamous cell carcinoma
Squamous cell carcinoma is easily treated if detected early, but it's slightly more apt to spread than is basal cell carcinoma. Most often, squamous cell carcinoma appears as one of the following:
• A firm, red nodule on your face, lips, ears, neck, hands or arms
• A flat lesion with a scaly, crusted surface on your face, ears, neck, hands or arms
This is the most serious form of skin cancer and the one responsible for most skin cancer deaths. Melanoma can develop anywhere on your body, in otherwise normal skin or in an existing mole that turns malignant. Melanoma most often appears on the trunk, head or neck of affected men. In women, this type of cancer most often develops on the arms or legs.
Warning signs of melanoma include:
• A large brownish spot with darker speckles located anywhere on your body
• A simple mole located anywhere on your body that changes in color, size or feel or that bleeds
• A small lesion with an irregular border and red, white, blue or blue-black spots on your trunk or limbs
• Shiny, firm, dome-shaped bumps located anywhere on your body
• Dark lesions on your palms, soles, fingertips and toes, or on mucous membranes lining your mouth, nose, vagina and anus
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. Like melanoma, it's a serious form of skin cancer. It's mainly seen 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.
• Merkel cell carcinoma. In this rare cancer, firm, shiny nodules occur on or just beneath the skin and in hair follicles. The nodules may be red, pink or blue and can vary in size from a quarter of an inch (about 6 millimeters) to more than 2 inches (about 50 millimeters). Merkel cell carcinoma is usually found on sun-exposed areas on the head, neck, arms and legs. Unlike basal and squamous cell carcinomas, Merkel cell carcinoma grows rapidly and often spreads to other parts of the body.
• 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 benign conditions.
Precancerous skin lesions, such as an actinic keratosis, also can develop into squamous cell skin cancer. Actinic keratoses appear as rough, scaly, brown or dark-pink patches. They're most commonly found on the face, ears, lower arms and hands of fair-skinned people whose skin has been damaged by the sun.
Not all skin changes are cancerous. The only way to know for sure is to have your skin examined by your doctor or dermatologist.