Squamous cells are, in essence, lining cells. They are thin, flat cells that make up the surface of the skin and the mucous lining of the esophagus, trachea (windpipe), and some organs. Squamous cell carcinoma is when the cancer forms in the squamous cells.
Squamous cell carcinomas are common in non-melanoma skin cancer and larynx (voice box) cancer. If caught early, squamous cell cancer is treatable. However, it does have the potential to metastasize, or spread.