Squamous Cell Carcinoma



Squamous cell carcinoma, the second most common skin cancer after basal cell carcinoma, afflicts more than 100,000 Americans each year.  It arises from the epidermis and resembles the squamous cells that compromise 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 or 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 green, blue 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 they do develop, however, are squamous cell carcinomas, usually arising on the sites of preexisting inflammatory skin conditions or burn injuries. 

What to Look For

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 changes in pigmentation and exhibits loss of elasticity. A lesion suspicious for SCC may appear like any of the following:

  • A persistent, scaly, red patch with irregular borders that sometimes crusts or bleeds.
  • An elevated growth with a central depression that occasionally bleeds.  A growth of this type may rapidly increase in size.
  • A wart-like growth that crusts and occasionally bleeds.
  • An open sore that bleeds and crusts and persists for weeks.

The lesions themselves usually appear as thickened, rough, scaly patches, which can bleed if bumped.  They often resemble warts.  Occasionally, an open sore will develop with a raised border and a crusted surface over an elevated, pebbly base.