Squamous cell carcinoma is a type of cancer that begins in the squamous cells, which are thin, flat cells that form the surface of the skin. It is the second most common type of skin cancer and can occur in any area of the body, but is most common in parts exposed to the sun, such as the face, neck, and arms. Squamous cell carcinoma is mostly caused by long-term exposure to ultraviolet (UV) radiation. The risk of developing squamous cell carcinoma is increased in people who have fair skin, who work outdoors, or who use tanning beds. The signs and symptoms of squamous cell carcinoma include a scaly red patch, open sores, elevated growths with a central depression, and wart-like growths. Squamous cell carcinoma may also appear as a lump with a rough, scaly, or crusted surface. If left untreated, squamous cell carcinoma can spread to other areas of the body, including the lymph nodes and internal organs. In order to diagnose squamous cell carcinoma, a doctor may perform a biopsy, during which a small sample of the affected area will be taken and examined under a microscope. Treatment for squamous cell carcinoma typically involves surgery, radiation therapy, and/or topical medications. For more severe cases, chemotherapy and immunotherapy may also be used. Squamous cell carcinoma can be prevented by avoiding prolonged sun exposure, wearing protective clothing and sunscreen, and avoiding tanning beds. People should also regularly check their skin for any changes or growths and report any changes to their doctor. Early detection is key to successful treatment of squamous cell carcinoma.