Skin cancer is the most common form of cancer in the United States. It will affect approximately 1 in 3 Americans during their lifetime. Most skin cancers are related to intense and cumulative sun or ultraviolet (UV) radiation exposure. Fortunately, early detection, routine skin examinations, and use of sun protection make most of these skin cancers successfully treated.
Actinic keratosis, sometimes referred to as "solar keratosis," is the most common form of precancerous skin lesions. According to the Skin Cancer Foundation, actinic keratoses affect more than 10 million Americans. Individuals with green or blue eyes, light-colored hair, and freckling are most at risk for the development of AK's.
Actinic keratosis is of concern to dermatologists and patients because AKs are precursor lesions to squamous cell carcinoma. It is estimated that as many as 10% of AKs may develop into squamous cell carcinoma, the second most common form of skin cancer.
Actinic keratosis is directly related to one's lifetime exposure to the sun or UV radiation. Chronic sun exposure predisposes an individual to AK development. Both men and women are affected. However, men are more likely to have AK's due to more cumulative sun exposure and less likelihood of using sun protection or sunscreen.
Any area of sun exposure may develop actinic keratosis, but the scalp, face, ears, neck, arms, back of the hands and lower legs are frequently affected. When actinic keratoses occur on the lips, it is referred to as "actinic cheilitis." Individuals affected by actinic keratosis are commonly in their 50s and beyond, but it is not unusual for someone in their 20s or 30s to develop AKs if they have a history of heavy cumulative sun or UV exposure.
Actinic keratoses appear as rough, red, and scaly patches, bumps, or horns on the skin. Patients may misdiagnoses AK's for dry skin. They are often felt better than they are seen, and actinic keratosis feel like "sandpaper" when the finger is brushed across the area of the lesion.
Actinic keratosis is treated because of the risk of this precancer developing into full-blown squamous cell carcinoma. Most commonly, cryosurgery is performed, which involves freezing the skin with liquid nitrogen. Topical therapy is also an option, and is often used in combination with other treatments. 5-fluorouracil (5-FU), imiquimod (Aldara®, Zyclara®), and diclofenac (Solaraze®) creams may be used to treat visible clinical lesions as well as microscopic lesions that cannot yet be detected.
Chemical peeling and laser resurfacing also decrease the skin burden of actinic keratoses. Lastly, photodynamic therapy
is a means of treating an entire skin surface area for AK's. This procedure combines a topical solution (aminolevulinic acid) which is activated by various laser and light technologies to target precancerous lesions. Any suspicious lesions that do not respond to the above treatments may be biopsied to rule out an early skin cancer.
The use of sunblock and proper sun protection is critical in preventing new actinic keratosis lesions. Other topical treatments such as lactic acid cream or a retinoid may be combined with any of the above treatments to decrease the number of AK lesions over time.
Squamous Cell Carcinoma (SCC)
Squamous cell carcinoma (SCC) is the second most common form of skin cancer with nearly a half a million new cases diagnosed annually according to the Skin Cancer Foundation
This form of skin cancer most commonly presents as rough, red, scaly or crusted nonhealing spots that form growths that are irritated or painful. SCC's over time may ulcerate or bleed. At least 40-60% of squamous cell carcinomas can be traced back to a previously existing precancerous lesion called an actinic keratosis.
SCC can occur anywhere on the skin, including mucous membranes and the genital area. Squamous cell carcinoma occurs most commonly in areas of chronic sun exposure including the scalp, face, rim of the ears, lips, neck, arms, hands and legs. SCC may also develop in areas of chronic ulcers, burn scars, or areas of skin exposed to arsenic or chemical carcinogens.
Squamous cell carcinoma can be a more aggressive form of skin cancer. With time and untreated, squamous cell carcinoma can spread locally and has the potential to spread internally to other organs. It is estimated that 2-10% of SCCs metastasize elsewhere in the body. Approximately 2,500 deaths each year are due to squamous cell carcinoma of the skin according to the Skin Cancer Foundation
Squamous cell carcinoma must be treated. Surgical excision and Mohs micrographic surgery are the most commonly used treatment options. Electrodessication and curettage, in which the lesion is treated with repeated rounds of scraping and burning, has a cure rate that approaches surgical excision. Cryosurgery (freeze therapy with liquid nitrogen), radiation therapy, and photodynamic therapy may be used in select cases of SCC.
Topical treatments may be used before, during, or after treatment of squamous cell carcinoma. Sunblock use, proper photoprotection, and frequent full skin examinations are critical to preventing the development of further squamous cell carcinomas.
Basal Cell Carcinoma
Basal cell carcinoma (BCC) is the most common form of skin cancer, arising from the bottom (basal) layer of the epidermis. According to the Skin Cancer Foundation
, approximately 1 million new cases of basal cell carcinoma are diagnosed each year.
Basal cell carcinoma is related to sun exposure, especially when individuals have had a history of sunburns or intense, intermittent sun exposure. Patients with light hair or eye color, and a tendency toward freckling or burns are at highest risk.
A pearly, shiny, pink or red bump is the most common appearance for a basal cell carcinoma. BCC may also appear as a red patch, a scar like spot, or an open or bleeding sore. Basal cell most commonly occurs on the scalp, face, ears, neck, arms, hands, and legs.
Basal cell carcinoma has a low rate of metastasis but can be destructive to the area affected by the tumor. Left untreated, the BCC may destroy fat, muscle, cartilage and even bone, leading to disfiguring results. Basal cell carcinoma respond excellently to early treatment.
Treatment options for BCC include surgical, laser, and topical-based therapies. Surgical excision, Mohs micrographic surgery, and electrodessication and curettage are the most common forms of treatment. Photodynamic therapy and imiquimod cream may be used to treat superficial basal cell carcinomas. Radiation therapy and cryotherapy are occasionally used to treat BCC.
Continued sun protection and sunscreen use are necessary to decrease the development of new basal cell carcinomas. Regular, frequent full skin examinations by a dermatologist are critical in surveying the skin for new or recurrent skin cancers.
Mohs Micrographic Surgery
Mohs micrographic surgery is a skin sparing surgical technique that allows for 100% microscopic examination of the surgical skin margin. It is named after Dr. Frederic Mohs, the surgeon who developed this technique for skin cancer removal in the 1930s.
Mohs micrographic surgery is unique from other methods of skin cancer removal in that it allows immediate and complete visualization of the entire tissue margin of excised tissue samples. It is typically reserved for specific clinical scenarios. These include skin cancers that occur on the face or scalp, skin cancers in cosmetically or functionally important areas of the body such as the hands, feet, or genitalia, and for aggressive or recurrent skin cancers.
The Mohs surgical procedure is well tolerated and performed under local anesthesia. After identifying the skin cancer to be treated, the tumor is removed with a narrow clinical margin. The removed tissue is immediately sectioned, stained, marked and then prepared for frozen tissue examination in the doctor's office. The physician then examines all tissue sections under the microscope, looking at both the deep and side margins of the tissue specimen, allowing 100% micrographic examination of the tissue margins. If tumor is present along any of the margins, this is noted on the corresponding Mohs map, and a small additional piece of tissue is taken from the indicated area of the skin. This process of tissue removal, frozen tissue processing, and microscopic examination is repeated until all margins are clear. The resulting surgical defect is then closed by a variety of techniques including simple closure, skin flaps or grafts, or secondary intention healing.
Mohs micrographic surgery is completed in the office. Depending on the case, the procedure may take between 1 to 4 hours. Dermatologists who perform Mohs micrographic surgery have specialized residency, fellowship or other intensive training experience. These dermatologic surgeons have appropriate laboratory facilities and histotechnological staff.
The main advantage of Mohs micrographic surgery is its complete examination of the tissue margin. Some skin cancers are larger than anticipated, or have "roots" that may be missed if simple surgical excision with standard margins is performed. By taking small margins in successive stages, Mohs can spare valuable, healthy tissue so skin is spared and surgical reconstruction is aided.