Stage IV is divided into stages IVA, IVB, and IVC. In stage IVA, the tumor has spread to nearby tissues in the lip and oral cavity (mouth); and/or cancer has spread to one or more lymph nodes in the neck and the involved lymph nodes are 6 centimeters (about 2 inches) or smaller. In stage IVB, the tumor has spread to one or more lymph nodes that are larger than 6 centimeters; or cancer has spread to the muscles or bones in the oral cavity, or to the base of the skull, and/or the carotid artery (blood vessel that carries blood from the heart to the head). Cancer may also have spread to one or more lymph nodes in the neck. In stage IVC, the tumor has spread beyond the lip and oral cavity to other parts of the body. Cancer may have spread to the lymph nodes.