Tx; Primary tumor cannot be assessed
T0: No evidence of primary tumor
Tis: Carcinoma in Situ
T1: Tumor 2 cm or less in greatest dimension
T2: Tumor more than 2 cm but not more than 4 cm in greatest dimension
T3: Tumor more than 4 cm in greatest dimension
T4 (lip): Tumor invades through cortical bone, inferior alveolar nerve, floor of mouth, or skin of face (ie, chin or nose)
T4a: (oral cavity) Tumor invades adjacent structures (eg, through cortical bone, into deep [extrinsic] muscle of tongue [genioglossus, hyoglossus, palatoglossus, and styloglossus], maxillary sinus, skin of face)
T4b: Tumor invades masticator space, pterygoid plates, or skull base and/or encases internal carotid artery

NX: Regional nodes cannot be assessed
N0: No regional lymph node metastasis
N1: Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension
N2: Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension; or in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension; or in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension
  N2a: Metastasis in single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension
  N2b: Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension
  N2c: Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension
N3: Metastasis in a lymph node more than 6 cm in greatest dimension

Stage 0: Tis N0 M0
Stage I: T1 N0 M0
Stage II: T2 N0 M0
Stage III: T3 N0 M0, T1 N1 M0, T2 N1 M0, T3 N1 M0
Stage IVA: T4a N0 M0, T4a N1 M0, T1 N2 M0, T2 N2 M0, T3 N2 M0, T4a N2 M0
Stage IVB: Any T N3 M0, T4b Any N M0
Stage IVC: Any T Any N M1