Squamous cell carcinoma is cancer that originates in the squamous cells (keratinocytes).
Squamous cells (keratinocytes) are the main structural cells of the epidermis (the outer layer of skin). Squamous cell carcinoma usually develops on sun-exposed areas but may grow anywhere on the skin or in the mouth, where sun exposure is minimal. It may develop on normal skin but is more likely to develop in precancerous skin growths caused by previous sun exposure (actinic keratoses—see Sunlight and Skin Damage:Overview of Sunlight and Skin Damage). Squamous cell carcinoma is characterized by its thick, scaly, irregular appearance. Fair-skinned people are much more susceptible to squamous cell carcinoma than darker-skinned people. This type of cancer is also more likely to develop in chronic sores—such as chronic skin ulcers—or in skin that has been scarred, particularly by burns.
Squamous cell carcinoma begins as a red area with a scaly, crusted surface that does not heal. As it grows, the tumor may become somewhat raised and firm, sometimes with a wartlike surface. Eventually, the cancer becomes an open sore and grows into the underlying tissue.
Most squamous cell carcinomas affect only the area around them, penetrating into nearby tissues. However, some spread (metastasize) to distant parts of the body and can be fatal. Those that occur near the ears, lips, and in scars are more likely to spread.
This is an early form of squamous cell carcinoma that is confined to the epidermis and has not yet invaded the deeper layers of the skin. The affected skin is red-brown and scaly or crusted and flat, sometimes looking like a patch of psoriasis or dermatitis or a fungal infection (ringworm).
Diagnosis, Treatment, and Prevention
When doctors suspect squamous cell carcinoma, they do a biopsy to differentiate this skin cancer from similar-looking diseases.
Doctors treat squamous cell carcinoma and Bowen's disease by scraping and burning the tumor with an electric needle (curettage and electrodesiccation), by cutting the tumor out, or by applying chemotherapy drugs to the skin. A technique called Mohs microscopically controlled surgery may be used. Sometimes radiation treatments are used. These treatments are usually effective, and most people survive.
Squamous cell carcinoma that has spread to other parts of the body can be fatal. It is treated with radiation or chemotherapy, but treatment may not be effective.
Because squamous cell carcinoma is often caused by sun exposure, doctors recommend that people stay out of the sun and use protective clothing and sunscreen, starting in early childhood.
Last full review/revision October 2008 by Gregory L. Wells, MD