Stage IV oropharyngeal cancer is divided into stages IVA, IVB, and IVC. In stage IVA, cancer (1) has spread to the larynx, front part of the roof of the mouth, lower jaw, or muscles that move the tongue or are used for chewing. Cancer may have spread to one lymph node on the same side of the neck as the tumor and the lymph node is 3 centimeters or smaller; or (2) has spread to one lymph node on the same side of the neck as the tumor (the lymph node is larger than 3 centimeters but not larger than 6 centimeters) or to more than one lymph node anywhere in the neck (the lymph nodes are 6 centimeters or smaller), and one of the following is true: (1) tumor in the oropharynx is any size and may have spread to the epiglottis (the flap that covers the trachea during swallowing); or (2) tumor has spread to the larynx, front part of the roof of the mouth, lower jaw, or muscles that move the tongue or are used for chewing. In stage IVB, the tumor (1) surrounds the carotid artery or has spread to the muscle that opens the jaw, the bone attached to the muscles that move the jaw, nasopharynx, or base of the skull. Cancer may have spread to one or more lymph nodes, which can be any size; or (2) may be any size and has spread to one or more lymph nodes that are larger than 6 centimeters. In stage IVC, the tumor may be any size and has spread beyond the oropharynx to other parts of the body, such as the lung, bone, or liver.