Skin cancer is the most common of all human cancers. Some form of skin cancer is diagnosed in more than 1 million people in the United States each year.
Cancer occurs when normal cells undergo a transformation during which they grow and multiply without normal controls.
- As the cells multiply, they form a mass called a tumor. Tumors of the skin are often referred to as lesions.
- Tumors are cancerous only if they are malignant. This means that they encroach on and invade neighboring tissues because of their uncontrolled growth.
- Tumors may also travel to remote organs via the bloodstream or lymphatic system.
- This process of invading and spreading to other organs is called metastasis.
- Tumors overwhelm surrounding tissues by invading their space and taking the oxygen and nutrients they need to survive and function.
Skin cancers are of three major types: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma.
- The vast majority of skin cancers are BCCs or SCCs. While malignant, these are unlikely to spread to other parts of the body. They may be locally disfiguring if not treated early.
- A small but significant number of skin cancers are malignant melanomas. Malignant melanoma is a highly aggressive cancer that tends to spread to other parts of the body. These cancers may be fatal if not treated early.
Like many cancers, skin cancers start as precancerous lesions. These precancerous lesions are changes in skin that are not cancer but could become cancer over time. Medical professionals often refer to these changes as dysplasia. Some specific dysplastic changes that occur in skin are as follows:
- Actinic keratosis is a patch of red or brown, scaly, rough skin, which can develop into squamous cell carcinoma.
- A nevus is a mole, and dysplastic nevi are abnormal moles. These can develop into melanoma over time.
Moles (nevi) are simply growths on the skin. They are very common. Very few moles become cancer.
- Most people have 10-40 moles on their body.
- Moles can be flat or raised; some begin as flat and become raised over time.
- The surface is usually smooth.
- Moles are round or oval and no larger than ¼-inch across.
- Moles are usually pink, tan, brown, or the same color as the skin. Other colors are sometimes noted.
- An individual's moles usually look pretty much alike. A mole that looks different from the others should be examined by your health-care provider.
Dysplastic nevi are not cancer, but they can become cancer.
- People with dysplastic nevi often have a lot of them, perhaps as many as 100 or more.
- People with many dysplastic nevi are more likely to develop melanoma, either within an existing nevus or on an area of normal skin.
- Dysplastic nevi are usually irregular in shape, with notched or fading borders.
- Dysplastic nevi may be flat or raised, and the surface may be smooth or rough ("pebbly").
- Dysplastic nevi are often large, ¼-inch across or even larger.
- Dysplastic nevi are typically of mixed color, including pink, red, tan, and brown.
Recent studies demonstrate that the number of skin cancer cases in the United States is growing at an alarming rate. Fortunately, increased awareness on the part of Americans and their health-care providers has resulted in earlier diagnosis and improved outcomes.
Signs and symptoms
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 — the palms, spaces between the toes and the genital area. Skin cancer affects people of all skin tones, including those with darker complexions.
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 in otherwise normal skin or in an existing mole that turns malignant. Although it can occur anywhere on the body, melanoma appears most often on the upper back or face in both men and women.
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 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 to more than 2 inches. 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.
Doctors cannot explain why one person develops skin cancer and another does not. However, we do know that skin cancer is not contagious. You cannot "catch" it from another person.
Research has shown that people with certain risk factors are more likely than others to develop skin cancer. A risk factor is something that may increase the chance of developing a disease.
Studies have found the following risk factors for skin cancer:
- Ultraviolet (UV) radiation: UV radiation comes from the sun, sunlamps, tanning beds, or tanning booths. A person's risk of skin cancer is related to lifetime exposure to UV radiation. Most skin cancer appears after age 50, but the sun damages the skin from an early age.
UV radiation affects everyone. But people who have fair skin that freckles or burns easily are at greater risk. These people often also have red or blond hair and light-colored eyes. But even people who tan can get skin cancer.
People who live in areas that get high levels of UV radiation have a higher risk of skin cancer. In the United States, areas in the south (such as Texas and Florida) get more UV radiation than areas in the north (such as Minnesota). Also, people who live in the mountains get high levels of UV radiation.
UV radiation is present even in cold weather or on a cloudy day.
- Scars or burns on the skin
- Infection with certain human papillomaviruses
- Exposure to arsenic at work
- Chronic skin inflammation or skin ulcers
- Diseases that make the skin sensitive to the sun, such as xeroderma pigmentosum, albinism, and basal cell nevus syndrome
- Radiation therapy
- Medical conditions or drugs that suppress the immune system
- Personal history of one or more skin cancers
- Family history of skin cancer
- 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 growths may appear as rough red or brown patches on the skin. They may also appear as cracking or peeling of the lower lip that does not heal. Without treatment, a small number of these scaly growths may turn into squamous cell cancer.
- Bowen's disease: Bowen's disease is a type of scaly or thickened patch on the skin. It may turn into squamous cell skin cancer.
If you think you may be at risk for skin cancer, you should discuss this concern with your doctor. Your doctor may be able to suggest ways to reduce your risk and can plan a schedule for checkups.