Squamous Cell Carcinoma Information
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What Is Squamous Cell Carcinoma?
Squamous cell carcinoma, or squamous skin cancer, is a type of skin cancer that develops from the flat, squamous cells that are the primary cell type that makes up the outermost layer of the skin, the epidermis. Squamous cells produce a protein called keratin, which helps to provide a protective layer for the rest of the body. As squamous skin cells die, they get pushed to the surface and form a tough, horny layer called the stratum corneum. These dead cells are continuously sloughed off and replaced by new cells.
According to the American Cancer Society, approximately two out of every 10 non-melanoma skin cancers are squamous cell carcinomas. Non-melanoma skin cancers, which also include squamous cell carcinomas and a few other rare subtypes, are the most common form of cancer seen in the United States, with approximately 2.2 million cases each year.
This type of skin cancer is usually found on areas of the skin that have been exposed to the sun, such as the face, neck or ears, or on the back of the hand, but they can develop in other areas, such as in scars or skin ulcers, or in the genital region.
Some squamous cell skin cancers develop from actinic keratoses, a precancerous skin condition caused by overexposure to the sun. Actinic keratoses are generally small (less than 1/4 inch in diameter) pink- or flesh-colored rough spots that appear in sun-exposed areas in middle-aged or older individuals.
Another precursor of squamous cell skin cancer is squamous cell carcinoma in situ, or Bowen Disease. “In situ” means that the cancer cells are still entirely in the epidermis, and have not spread to the deeper layers of the skin. These spots usually appear reddish in color, and may be over 1/2 inch in diameter. They may be redder, scalier and more crusted than actinic keratoses. Squamous cell carcinoma in situ is usually found in sun-exposed areas, but may also appear in the genital or anal area, and these cases may be related to infection with human papilloma virus (HPV).
Squamous cell carcinomas usually grow slowly, and it is uncommon for them to spread, or metastasize, to nearby lymph nodes or more distant parts of the body. However, they are more likely than basal cell carcinomas to invade fatty tissue beneath the skin or to spread even further.
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