Squamous cell carcinoma develops in the outer layer of the skin (the epithelium), and can eventually spread to other body parts if it is not addressed in a timely manner.
It is the second most common type of skin cancer after basal cell carcinoma. It afflicts approximately 250,000 people per year, but causes only around 2,500 deaths in the same time period.
The term “squamous cell” refers to the flat, scale-like cells that comprise the surface of the skin, the linings of hollow internal organs, and the inner passages of the digestive and respiratory systems.
Squamous cell carcinoma may affect any of these areas, but it is most commonly seen on the outer layer of the skin. The vast majority of sufferers are middle-aged or older, with fair skin and a history of frequent exposure to the sun. Typically, squamous cell carcinomas are slow growing, and when they appear in combination with other types of sun damage, they may be very difficult to detect.
Signs and Symptoms
In some cases, squamous cell carcinomas emerge from small, rough lesions called solar or actinic keratosis. Although most squamous cell carcinomas appear on parts of the skin that are exposed to the sun, they may also be found in the mouth, anus, or genitals. Not all squamous cell carcinomas look alike. Some may appear as a firm, red nodule on the face, lower lip, ears, neck, hands, or arms.
When they affect the mouth, they appear as a flat, white patch or ulcer. In some cases, squamous cell carcinomas may appear on the face, ears, neck, hands, or arms as a flat lesion with a scaly crust, or as a raised area on a pre-existing scar or ulcer. When squamous cell carcinomas affect the anus or genitals, they typically appear as a raised patch or ulcerated sore.
The direct cause of squamous cell carcinoma is damage to DNA, which typically results from prolonged exposure to UV rays from the sun or commercial tanning beds. In normal skin, new cells (basal cells) are formed at the bottom layer of the epidermis, and are gradually pushed to the surface as they age. When DNA damage occurs, though, this process can be disturbed, causing the squamous cells in the next deepest layer of skin to grow out of control.
The most commonly cited cause of squamous cell carcinoma is exposure to UV light from the sun and tanning beds, but there are other known causes as well. First, use of immunosupressant drugs to prevent rejection after an organ transplant is an important risk factor. Up to eighty percent of transplant patients eventually develop squamous cell carcinomas.
Another cause of this condition is excessive exposure to arsenic through food, drinking water, or air. Therapeutic radiation treatments like x-rays, Psoralen UVA (PUVA) treatments for psoriasis, and radiation treatments for childhood acne or ringworm are also risk factors. Squamous cell carcinomas that afflict the genitals are often caused by exposure to Human papilloma-virus (HPV).
Those most at risk for developing squamous cell carcinoma are men, those with fair skin, and those with a personal history of cancer. People whose immune systems are weakened by disease and/or use of immunosupressants are also at higher-than-average risk for squamous cell carcinoma, as are individuals who have large scars, skin infections or inflammatory skin diseases like psoriasis.
Because their skin has a dramatically reduced ability to repair damage from ultraviolet light, people who have the rare genetic disorder xeroderma pigmentosum have a much higher risk of developing skin cancer of all kinds, including squamous cell carcinoma.
Since squamous cell carcinoma can metastasize, (spread to other parts of the body) people who experience any of the symptoms described above are usually advised by their doctors to undergo a biopsy as quickly as possible.
This procedure involves removing anywhere from a few layers of skin from the top of the affected area to a larger section of the tumor, depending on the size of the carcinoma. This sample is then sent to a pathologist for analysis.
The most effective and appropriate treatment for squamous cell carcinoma depends on the size and location of the problem area, as well as whether or not the cancer has metastasized. For minor carcinomas on the lips, laser therapy is often used. Small squamous cell carcinomas may also be treated by freezing them, excising them, or applying a chemotherapeutic cream.
In cases where it is important to absolutely minimize the amount of skin that is removed, doctors may use Moh’s surgery, a process where the affected skin is removed layer by layer until all afflicted cells are gone.