Nonmelanoma skin cancer

Nonmelanoma skin cancer continues to be the most common type of malignancy associated with the Caucasian population in the United States. In 1996, more than 800,000 cases of nonmelanoma skin cancer were diagnosed in the United States. It has been estimated that there will be approximately 2.75 million newly diagnosed skin cancer cases worldwide each year.(1) The Environmental Protection Agency estimates that there will be 12 million new cases of nonmelanoma skin cancer in the United States within the next 50 years.(2)

Data about the incidence of nonmelanoma skin cancer has been difficult to gather. The low mortality rate and traditional treatment in the outpatient setting has made data collection problematic. Research gathered from other countries concluded that there is a correlation between ultraviolet radiation exposure, the degree of skin pigmentation, and the chance of developing skin cancer. For example, Caucasians who live close to the equator have a higher chance of developing nonmelanoma skin cancer. People with dark skin tones have a much lower incidence of skin cancer, which is primarily due to their darker skin pigmentation.

The possibility of developing skin cancer also is related to gender. Older men are more likely to develop skin cancer than women, and the risk of skin cancer may depend on cumulative sun damage. Approximately 80% of men and women have occurrences of skin cancer on the face, head, or neck. It is interesting to note, however, that most skin cancer in men occurs on the ears or nose, and women are prone to develop skin cancer on the nose or lower extremities. This may be attributed to gender-related occupational exposure.(3)

The two most common types of nonmelanoma skin cancers are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). These cancers account for the majority of skin cancers treated, with BCC being the most common, representing approximately 75% of the cases. Occurrences of BCC and SCC are two to three times more frequent in men, which may be attributed to the fact that more men are employed in outdoor occupations and exposed to the sun on a regular basis.(4)

Clinical studies suggest that there is a link between the development of skin cancer and the immune system. Studies involving mice have shown evidence that the immune system is important in tumor recognition and tumor control.(5) It is known that immunosuppression increases the risk of both melanoma and nonmelanoma skin cancers. Immunosuppressed patients (eg, organ transplant, HIV/AIDS, and medically immunosuppressed patients) are at risk for developing skin cancer due to their condition.(6)

BASAL CELL CARCINOMA

Basal cell carcinoma is the most common malignancy found in today's population. It is a malignant tumor of the skin that comes from the basal layer of cells found in the epidermis of the skin (Figure 1). Basal cell carcinoma is also called basal cell epithelioma, rodent ulcer, and Jacob's ulcer.(7) This type of skin cancer primarily has been diagnosed in older adults, although recently it has become common in patients who are younger than 40. This change has been attributed to lifestyles that encourage more time outdoors with frequent sun exposure.

[Figure 1 ILLUSTRATION OMITTED]

Basal cell carcinomas traditionally are slow-growing tumors that rarely metastasize to other parts of the body. Growth of BCC tumors usually is localized to the area of origin; however, this type of tumor has very significant infiltrative behavior. Neglect or incomplete removal of a BCC can result in significant patient morbidity. Histological variants of BCC are that the tumor is nodular, micronodular, superficial, infiltrative, and morpheaform. A BCC usually appears as a slightly raised pearl-colored papule with a well-defined border. Other BCCs may be subtler, with an appearance similar to a scar or dermatitis. A definitive diagnosis of BCC usually is made by performing a biopsy.(8)

Recurrent BCC can occur many years after the original eradication of the tumor. The BCC cells may be hidden in the previous surgical scar and difficult to diagnose. Patients with a history of BCC are encouraged to routinely follow up with a trained professional to recognize a recurrence of the tumor.

Although metastatic lesions with BCC are rare, they do occur in 0.0028% to 0.1% of the population. When it metastasizes, BCC behaves like other metastatic skin cancers and typically spreads to the lymph nodes, liver, bone, and lungs.(9)

Many treatment options exist for patients with BCC, including rumor destruction by various methods (eg, liquid nitrogen cryosurgery, electrodessication and curettage, Mohs micrographic surgery, traditional surgical excision with margin control). The ultimate goal when treating BCC is eradication of the tumor in a manner that is cost-effective and curative and has minimal morbidity.

Patients with BCC must plan on frequent followup visits to make sure that there is no recurrence of the lesion. It is important that these patients begin preventive measures to decrease their future chances of developing new lesions by not only using sunscreen but also by avoiding direct sun exposure. Patient education is an important factor in the early discovery of additional cancers, and patients are encouraged to seek immediate care when an area of concern is first noticed.

SQUAMOUS CELL CARCINOMA

Squamous cell carcinoma is not as common as BCC, but its rate of increase is much higher. It is estimated that for the past 30 years the incidence of SCC has been increasing 4% to 8%. This is significant because this type of cancer has a mortality rate equal to melanoma (ie, 1% to 2%).(10) Studies have noted that the five-year survival rate for patients with SCC with lymph node metastasis is 50% or less.

Initial curative resection is important because recurrent SCC tumors are much more likely to metastasize.(11) This is particularly important for organ transplant recipients as it has been hypothesized that patients with medically weakened immune systems can no longer combat early tumor formation and immunosuppressive therapy may very well potentiate the effects of previous sun damage.(12)

Squamous cell carcinoma lesions vary in appearance and usually appear as dull, red lesions with scaling and induration (Figure 2). They also may be dome-shaped with a crusty layer or ulceration. Although SCC can be seen on skin that has been exposed to the sun, lesions especially are common on the lips and appear as a thickened area on a dry, scaly surface of the vermilion border (ie, the external pink to red area of the lips). Another common site for SCC is the dorsal area of the hands, where BCC is rarely seen.

[Figure 2 ILLUSTRATION OMITTED]

A diagnosis of SCC is made by performing a biopsy of the suspicious lesion. Squamous cell carcinomas that are well differentiated usually are less prone to recur or metastasize and less aggressive lesions. Squamous cell carcinomas that are large, poorly differentiated, or deeply invasive metastasize more frequently and often lead to a poor prognosis.

These lesions have the potential to develop regional metastases. A patient who reports a rapidly growing lesion should be seen immediately, as the typical SCC is rapid growing. There are lesions that appear on the skin that are variants of SCC (eg, keratoacanthoma) (Figure 3). A biopsy often is necessary to differentiate keratoacanthoma from SCC.

[Figure 3 ILLUSTRATION OMITTED]

Treatment modalities for SCC depend not only on the location and size of the tumor but also include its potential for metastasis. Smaller tumors may be treated with liquid nitrogen cryosurgery, electrodessication, and curettage. Surgical excision that provides removal of the lesion and clear margins is the optimal treatment for lower risk tumors, and Mohs micrographic surgery tends to be the treatment of choice for high-risk tumors. High-risk tumors are defined as tumors that are at a higher risk for metastasis, show tumor invasion around nerves, or are in sensitive areas such as the nose, ear, lip, or penis. Excisions are performed with tissue sparing in mind to provide clear margins, as reconstruction in these areas is difficult.

The first five years after diagnosis is crucial for the patient diagnosed with SCC. Frequent follow-up with a trained professional is essential, as more than 75% of recurrences are seen in these patients within a two-year period, and more than 80% of metastases occur within this same time frame.(13) Patients diagnosed with SCC must be educated on the benefits of applying sunscreen and avoidance of the sun.

PREVENTION