Squamous Cell Carcinoma of the Skin

What Is It?

Squamous cells are small, flat skin cells in the outer layer of skin. When these cells become cancerous, they typically develop into flat or raised, rounded skin tumors. Sometimes the skin around the tumors gets red and swollen.

Most cases of squamous cell carcinoma occur in people who have spent lots of time in the sun—especially those with fair skin and blue eyes. Some cases develop on skin that has been injured or exposed to cancer-causing agents. This type of squamous cell cancer can develop on:

  • Scars, burns, and long-lasting ulcers

  • The legs and body of workers exposed to poisons, harsh chemicals, and agents like tar and soot

  • Skin affected by genital warts

  • Red patches of skin covered with white scales, a condition called psoriasis, treated with certain therapies.

People with a weakened immune system are at especially high risk of developing squamous cell cancer. This includes people who:

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