Tumor Site Descriptions
Oral Cavity:
Mucosa of lip, Tongue (border, surface, or anterior 2/3), Upper or lower gum, Floor of mouth, Hard palate, Cheek mucosa, Retromolar area
Oropharynx:
Oropharynx, Base of tongue, Tonsil, Soft palate, Uvula, Vallecula
Hypopharynx:
Hypopharynx, Pyriform sinus
Nasopharynx:
Nasopharynx (Superior, posterior, lateral, or anterior wall)
Larynx:
Larynx (Glottis, subglottis, supraglottis, or laryngeal cartilage), Anterior surface of epiglottis

Tumor Extension Descriptions (Oral Cavity and Oropharynx)
Localized:
Tumor is confined to primary site of origin
Extension, not T4:
Tumor extends beyond site of origin, but does not extend to the regions that would classify it as T4a or T4b (see below)
Extension, T4a:
Tumor invades through bone, to deep/extrinsic muscles of tongue, to maxillary sinus or skin of face (oral cavity), or to medial pterygoid or hard palate (oropharynx)
Extension, T4b:
Tumor encases internal carotid artery or invades skull base, pterygoid plates, masticator space (oral cavity), or lateral pterygoid muscle or lateral nasopharynx (oropharynx)