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Squamous Cell Carcinoma

Overview

Squamous cell carcinoma (SCC) is the second most common type of skin cancer. It involves the malignant transformation and proliferation of squamous (flat, scaly) cells, which are the most abundant type of cell in the epidermis. Cutaneous squamous cell carcinoma is usually localized, but it can metastasize. When confined to the skin, it is easily treated and cured. In most cases, cutaneous SCC develops in patients with known factors, such as excessive exposure to the sun.

Patients with fair skin and a history of sun exposure (e.g., sunburn) are at increases risk for SCC, as well as other forms of skin cancer. These people lack pigmentation, which protects the skin from damaging ultraviolet rays.

Causes

The greatest risk for SCC occurs in light-skinned individuals with excessive sun exposure. The cumulative damage, particularly after repeated sunburns, causes abnormal changes (mutations) in cellular DNA. DNA contains the genetic blueprint and once the genetic blueprint is altered, all subsequent cellular division duplicates the defect. The defective cells multiply rapidly and cause a tumor to form.

Ultraviolet rays are not the only predisposing factors for developing SCC. Additional factors can be significant, depending on the individual. These include excessive exposure to radiation or x-rays, exposure to arsenic (a chemical found in some well water), and excessive exposure to tars, soot, and some industrial oils. In addition, SCC is more likely to develop in chronic ulcers and in burn scars and other scar tissue. Scar SCC usually develops years after the original injury. Individuals who are chronically immunosuppressed, such as by medication or disease, are predisposed to the development of skin cancer as well.

Signs and Symptoms

When SCC is confined to the epidermis, it is called squamous cell carcinoma in-situ, sometimes referred to as Bowen's disease. It becomes invasive when it penetrates through the epidermis and into the dermis.

Lesions appear as pink, rough, scaly patches or nodules that have a tendency to bleed. The growth is typically firm and sometimes extends inward as well as outward in the skin. As the tumor grows, it ulcerates and scabs over.

SCC frequently develops on the face, lips, ears, and hands. Metastasis to other parts of the body can occur. The incidence of metastatic SCC varies; however, larger and deeper lesions especially on the lips, hands, temples, and ears are more likely to spread.

Diagnosis and Tests

A suspected SCC, especially lesion that does not heal, should always be biopsied (i.e., cells are removed and evaluated under a microscope). In addition to confirming the diagnosis, biopsy can distinguish SCC from other types of malignant tumors that may require more aggressive therapies.

Treatment

The choice of treatment is based on a variety of factors including size and location of the lesion, type of tumor, and age of the patient.

SCC in-situ can be eradicated by curettage and desiccation, a procedure used to scrape out and burn all the cancer cells. Invasive SCC that is small and not deep (superficial) can be treated using this procedure as well.

Small and large SCC can be excised (cut out). With surgical excision, a margin of healthy appearing tissue is removed along with the tumor to reduce the risk for recurrence. The skin is removed through the third layer, the subcutaneous fat, and is usually sutured (stitched) closed. In most cases, results are cosmetically acceptable. The excised tissue is sent to a pathologist to check the margins (i.e., the side and deep edges of the tissue) to ensure that all the cancer has been removed. Occasionally, cancer cells are found in the margins and a second, similar procedure is performed to remove remaining cancer cells.

A specialized form of surgery (called Mohs micrographic surgery) may be performed, especially when the tumor is large, has poorly defined edges, or develops on areas of the body where the scar outcome is more important (e.g., on the face). Mohs surgery involves removing the tumor with a relatively small margin of healthy appearing tissue. While the patient waits, the surgeon examines all the edges thoroughly to determine if and where any cancer cells remain. When more tissue needs to be taken, the surgeon removes a portion only in the area of the cancerous cells, thus excising as little of the healthy skin as possible. When the procedure is complete, the wound is closed and repaired to minimize scarring. The recurrence rate for skin cancer removed by Mohs micrographic surgery is about 2%, while the recurrence rate associated with traditional excision varies from 5% to 10%.

Radiation therapy is an effective option for many tumors, especially large lesions on the nose, lips, and eyelids, and for patients unable to undergo surgical excision. Radiation destroys tumor cells along with some surrounding healthy tissue. The scar is usually lighter and forms a depression.

Cryosurgery, treatment of skin lesions with liquid nitrogen, may be used in some cases. The wound created by the procedure usually heals within 4 weeks and the resulting scar is similar to that made by curettage and desiccation.

SCC that has spread to lymph nodes or distant sites (metastasized) can be treated using surgery and additional radiation or chemotherapy. An oncologist is usually consulted at this point.

Prevention

Avoiding or minimizing sun exposure may help prevent many cases of SCC. Applying sunscreen every day on all exposed areas, including the lips and ears, is helpful. Self-examination is important for early detection. It is easier to treat smaller skin cancers, and the risk of spreading is reduced in smaller lesions.

Skin Cancer, Squamous Cell Carcinoma reprinted with permission from oncologychannel.com
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