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Squamous cell carcinoma, the second most common skin cancer after
basal cell carcinoma, afflicts more than 200,000 Americans each
year. It arises from the epidermis and resembles the squamous cells
that comprise most of the upper layers of skin. Squamous cell cancers
may occur on all areas of the body including the mucous membranes,
but are most common in areas exposed to the sun.
Although
squamous cell carcinomas usually remain confined to the epidermis
for some time, they eventually penetrate the underlying tissues
if not treated. In a small percentage of cases, they spread (metastasize)
to distant tissues and organs. When this happens, they can be fatal.
Squamous cell carcinomas that metastasize most often arise on sites
of chronic inflammatory skin conditions or on the mucous membranes
or lips.
What
Causes It
Chronic exposure to sunlight causes most cases of squamous cell
carcinoma. That is why tumors appear most frequently on sun-exposed
parts of the body: the face, neck, bald scalp, hands, shoulders,
arms, and back. The rim of the ear and the lower lip are especially
vulnerable to the development of these cancers.
Squamous
cell carcinomas may also occur where skin has suffered certain kinds
of injury: burns, scars, long-standing sores, sites previously exposed
to X-rays or certain chemicals (such as arsenic and petroleum by-products).
In addition, chronic skin inflammation or medical conditions that
suppress the immune system over an extended period of time may encourage
development of squamous cell carcinoma.
Occasionally,
squamous cell carcinoma arises spontaneously on what appears to
be normal, healthy, undamaged skin. Some researchers believe that
a tendency to develop this cancer may be inherited.
Who
Gets It
Anyone with a substantial history of sun exposure can develop squamous
cell carcinoma. But people who have fair skin, light hair, and blue,
green, or gray eyes are at highest risk. Those whose occupations
require long hours outdoors or who spend extensive leisure time
in the sun are in particular jeopardy. Dark-skinned individuals
of African descent are far less likely than fair-skinned individuals
to develop skin cancer. More than two thirds of the skin cancers
that they do develop, however, are squamous cell carcinomas, usually
arising on the sites of preexisting inflammatory skin conditions
or burn injuries.
Precancerous
Conditions
Certain precursor conditions, some of which result from extensive
sun damage, are worth noting. They are sometimes associated with
the later development of squamous cell carcinoma. They include:
- Actinic,
or solar, keratosis. Actinic keratoses are rough, scaly,
slightly raised growths that range in color from brown to red
and may be up to one inch in diameter. They appear most often
in older people.
- Actinic
cheilitis. A type of actinic keratosis occurring on
the lips, it causes them to become dry, cracked, scaly, and
pale or white. It mainly affects the lower lip, which typically
receives more sun exposure than the upper lip.
- Leukoplakia.
These white patches on the tongue or inside of the mouth have
the potential to develop into squamous cell carcinoma.
- Bowen's
disease.
This is now generally considered to be a superficial squamous
cell cancer that has not yet spread. It appears as a persistent
red-brown, scaly patch which may resemble psoriasis or eczema.
If untreated, it may invade deeper structures.
Regardless
of appearance, any change in a preexisting skin growth, or the development
of a new growth or open sore that fails to heal, should prompt an
immediate visit to a physician. If it is a precursor condition,
early treatment will prevent it from developing into a squamous
cell carcinoma. Often, all that is needed is a simple surgical procedure
or application of a topical chemotherapeutic agent.
Squamous
cell carcinomas occur most frequently on areas of the body that
have been exposed to the sun for prolonged periods. Usually, the
skin in these areas reveals telltale signs of sun damage, such as
wrinkling, changes in pigmentation, and loss of elasticity.
Warning
Signs of Squamous Cell Carcinoma
What
To Look For: Moles vs. Melanoma
Basal
Cell Cancer
Resources:
Skin Cancer Foundation
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