oropharyngeal cancer (or-oh-fuh-RIN-jee-ul KAN-ser) Cancer that forms in tissues of the oropharynx (the part of the throat at the back of the mouth, including the soft palate, the base of the tongue, and the tonsils). Most oropharyngeal cancers are squamous cell carcinomas (cancer that begins in flat cells lining the oropharynx).

oropharynx (or-o-FAIR-inks) The part of the throat at the back of the mouth. It includes the soft palate, the base of the tongue, and the tonsils.

stage I oropharynx cancer Cancer that is no larger than 2 centimeters (about 0.75 inch) and is confined to the oropharynx.

stage II oropharynx cancer Tumor that is between 2 and 4 centimeters (0.75 and 1.5 inches) and is confined to the oropharynx.

stage III oropharynx cancer The tumor is larger than 4 centimeters (about 1.5 inches) in size and may involve a single lymph node on the same side of the neck.

stage IV oropharynx cancer The tumor has spread to the hard palate, tongue, or larynx, to nearby lymph nodes, and may have spread to other parts of the body.