Like basal cell carcinomas, squamous cell carcinomas are most common in sun-exposed areas, however, the distribution is different with the backs of the hands, forehead, and scalp being commonly affected sites. Unlike basal cell carcinomas, squamous cell carcinomas can metastasize to the lymph nodes and lungs.
Especially aggressive squamous cell carcinomas are those that arise in scars, previous radiation or burn sites, or chronically inflamed or ulcerated skin.
Arsenic exposure and the human papilloma virus (HPV) also increase the risk of squamous cell carcinoma. It is important to note that for African Americans this tumor can present in a different distribution, and will most often affect the groin area and legs. This is a serious form of skin cancer and any red, sore, crusty or scaly patch, bump, nodule, or horn should be evaluated by a dermatologist as soon as possible.