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.
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