A malignant tumor originating in the cells that cover the mucous membrane lining the throat. Throat cancer is also known as cancer of the pharynx. This cancer tends to penetrate the mucous membrane and muscle layers, spreading into surrounding tissue as it grows. It can spread to lymph nodes in the neck and into the bloodstream and be carried to the lungs and other organs. Cancers near the mouth tend to remain localized unless they are not successfully treated. Cancers near the nose and in the lower throat may spread early before symptoms appear.