The skin changes that result in cancer develop over the years and may take decades to produce a malignancy. Thus, skin cancer usually shows up in older people. However, Americans are developing skin cancer at ever-younger ages because of the increasing amounts of time spent in the sun (as well as time spent in indoor tanning booths). Prolonged sun exposure is the principal cause of the most common types of skin cancer.
Basal cell carcinoma is the most prevalent type of skin cancer. The most common site for basal cell carcinoma is the face, especially the nose or ears, but it can appear anywhere. It is painless and slow-growing and rarely spreads to other parts of the body.
Squamous cell carcinoma typically develops on the face (especially the lips and nose), the rim of the ear, and the back of the hands but can also appear elsewhere. If not treated, the lesions—notably large ones on the face and neck—can grow and spread, although this is rare. Squamous cell carcinoma is often preceded by precancerous lesions called actinic keratoses.
Each year, more than 5 million basal and squamous cell skin cancers are diagnosed in the U.S.; about 80 percent of these are basal cell carcinoma. Fortunately, both basal cell and squamous cell skin cancers have about a 95-percent non-recurrence rate when detected and treated early.
Melanoma is by far the least prevalent of the three common skin cancers, but it is the most dangerous. An estimated 87,000 new cases are diagnosed in the U.S. every year, with incidence having doubled since 1973; about 9,000 deaths annually are attributed to melanoma. White people are at 20 times greater risk than black people; overall, about 1 in 38 will develop melanoma.
Melanoma develops from melanocytes—cells located in the epidermis that produce melanin, the dark pigment that helps protect the skin from the sun’s ultraviolet radiation. Melanocytes are scattered throughout the epidermis and can also aggregate and form benign moles. Melanoma occurs when melanocytes begin reproducing uncontrollably to form malignant tumors.
Are you at risk?
Your risk increases with age—adults ages 55 to 75 are 100 times more likely to develop basal cell carcinoma than people younger than 20. Besides sun exposure, other risk factors for basal cell and squamous cell carcinoma include fair skin; a history of radiation therapy; exposure to certain ultraviolet light treatments; a weakened immune system or immunosuppressive therapy; exposure to arsenic (sometimes found in well water and insecticides); smoking tobacco; a history of trauma to the skin or severe burns (such as those caused by heat, chemicals, or electricity); and human papillomavirus (HPV).
It is clear that the risk of basal and squamous cell carcinoma rises in proportion to the cumulative amount of time people have spent in the sun. But the sun’s role in the development of melanoma is less clear, and in fact surprisingly little is known about what causes melanoma. People who spend lots of time in the sun (such as farmers) do not have elevated rates of melanoma, though they do have higher rates of squamous and basal cell carcinoma, and melanoma incidence has grown even as sunscreen use has increased. Melanoma often turns up on parts of the body rarely exposed to the sun (such as the buttocks, scalp, and soles of the feet).
People who have fair skin, red or blond hair, and/or lots of freckles (especially on the upper back) are at elevated risk for melanoma. If you have a family history of melanoma or have had three or more blistering sunburns as a child or teenager, your risk also increases.
Genetic factors—including those that affect skin and hair color and the type and number of moles—clearly play a role in melanoma. But genetics can’t explain the increase in melanoma incidence over the past three generations.
In March, the U.S. Preventive Services Task Force updated recommendations to advise counseling young adults, adolescents, and parents of children as young as six months about avoiding ultraviolet radiation in order to prevent skin cancer.
Basal and squamous cell skin cancers appear as abnormal changes, sometimes subtle, to an area of the skin. The abnormality may look like:
- A rounded pink or skin-colored growth with visible blood vessels or brown or black spots, which may sink in the center like a crater and ooze, become crusty, or bleed easily.
- A shiny pink patch.
- A red, rough and scaly growth.
- A waxy, hard, pale growth, which may resemble a scar.
- A growth with no definitive edges.
- A non-healing sore.
- A solitary flattened, reddish, scaly, or eczema-like patch.
A skin biopsy, which involves removal of part or all of the growth for analysis, is the only way to know for sure whether a growth is cancerous. If a biopsy shows the presence of cancer, your treatment options will depend on the type of cancer; its location, size, and stage; treatment side effects such as scarring; and your age, overall health, and skin cancer history.
In some cases, your doctor will have already removed the entire growth for a biopsy, and no further treatment is needed.
If not, your doctor may recommend one of two primary surgical methods to treat basal or squamous cell skin cancers, both of which provide a confirming biopsy:
- Surgical excision can be performed using local anesthesia in an outpatient setting. It typically results in a one- to two-week healing period and often leaves a scar.
- Mohs micrographic surgery (named for surgeon Frederic Mohs), a more time-consuming and costly procedure, is typically reserved for tumors that have an increased risk of recurrence and are in visible areas such as the face. Because Mohs preserves more tissue, it leaves smaller scars.
Your doctor may also recommend other treatments in addition to or instead of surgery. These include:
- Radiation therapy used as a primary treatment is typically reserved for patients over age 60 who can’t tolerate surgery or who have tumors that can’t be surgically removed because of their size or location.
- Electrodessication and curettage involves scraping away the tumor and using electricity to kill any remaining cancer cells.
- Photodynamic therapy uses a combination of a chemical applied to the lesion and a special light directed at the treatment site to destroy cancer cells.
- Topical prescription creams, ointments, or gels can be applied directly to an early-stage growth or lesion.
- Oral medications such as vismodegib (Erivedge) and sonidegib (Odomzo), known as antineoplastic hedgehog inhibitors, affect the regulation of cell growth.
- Cryotherapy uses liquid nitrogen to freeze and destroy small, non-invasive, low-risk lesions.
Because skin cancer recurrence is most common in the first five years after treatment, it’s crucial to see your dermatologist regularly for a full body check.
General signs of melanoma include:
- A mole that begins to enlarge, thicken, or change color. Some 70 percent of early-stage lesions are identified because of recent changes in size, color, border contours, or surface texture.
- A mole that appears different from other moles (a so-called “ugly duckling”).
- A mole that suddenly begins to grow, or one that bleeds or ulcerates.
- A mole that has irregular rather than round borders.
- A mole with irregular pigmentation—some portions light colored, others almost black.
If you see anything suspicious, get medical advice. If malignant melanoma is detected, you should see a doctor with special expertise in melanoma. The treatment is prompt surgical removal. If a melanoma is removed in the later stage, when the cancer has begun to invade the surrounding tissues or other areas of the body, the survival rate drops sharply compared to removing melanoma in the early stages.
This article first appeared in the UC Berkeley Wellness Letter.