Squamous cell carcinoma is the second most common type of skin cancer, affecting 250,000 Americans annually. So what is squamous cell carcinoma? Squamous cell carcinoma, or SCC, is a type of cancer that forms on the skin's outermost layer. If left untreated and allowed to spread, SCC can cause severe scarring or - in up to 4% of cases - death. The best way to avoid these consequences is to avoid the sun! Like 90% of skin cancers, SCC almost always arises from overexposure to the sun's harmful ultraviolet rays. Chronic sun exposure isn't the only factor that can make you a more likely candidate to develop SCC - however, knowing if you're a high risk candidate can help you to protect yourself. Unlike the other types of non-melanoma skin cancer, SCC can arise from chronically scarred or inflamed skin. The human papillomavirus, which often causes warts, can also lead to SCC. People with weakened immune systems, or immunosuppression, have a higher risk of developing SCC. Possible causes of a weak immune system include the HIV virus and organ transplant medication. As with other skin cancers, people with fair skin, light hair, and blue or green eyes have a higher risk of developing SCC. Many doctors believe that a family history of the disease - or a personal history of any cancer - may also be factors. SCC crops up most frequently in the male population over 40, so older men need to be extra vigilant about checking their skin for signs of cancer. While being aware of your risk factors is the first step to keeping yourself safe from SCC, it's also important to know how skin cancer manifests itself and what it looks like. SCCs develop form keratinocytes, the tough-walled cells that make up 90% of the skin's outer layer. Years of sun damage can cause these cells to change in size and shape, resulting in the tumors that are characteristic of SCC. Often, SCCs appear first as rough, scaly patches on the skin. These precancerous lesions, known as actinic keratoses, or AKs, can eventually develop into SCC. The typical SCC manifests itself as a new or enlarging tumor that is thick and rough. Most tumors emerge on the head or neck, although any skin can be affected. Squamous cell carcinoma often appears to be a wart-like growth or a scaly, red patch that crusts on the top, and occasionally bleeds. Sometimes, SCC begins as an open sore that continuously bleeds and crusts for weeks at a time without really healing. If left untreated, squamous cell carcinoma can spread to vital organs and cause death, so it's imperative to see a doctor any time you notice changes in the appearance or texture of your skin. Want to learn more? Check out other videos and sources on this site for more information.