Primary tumor (T)

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

   [Note: Superficial erosion alone of bone/tooth socket by gingival primary is not sufficient to classify a tumor as T4.]

Regional lymph nodes (N)

• NX: Regional lymph nodes cannot be assessed
• N0: No regional lymph node metastasis
• N1: Metastasis in a single ipsilateral lymph node, ≤3 cm in greatest dimension
• N2: Metastasis in a single ipsilateral lymph node, >3 cm but ≤6 cm in greatest dimension; or in multiple ipsilateral lymph nodes, ≤6 cm in greatest dimension; or in bilateral or contralateral lymph nodes, ≤6 cm in greatest dimension
  • N2a: Metastasis in a single ipsilateral lymph node >3 cm but ≤6 cm in dimension
  • N2b: Metastasis in multiple ipsilateral lymph nodes, ≤6 cm in greatest dimension
  • N2c: Metastasis in bilateral or contralateral lymph nodes, ≤6 cm in greatest dimension
• N3: Metastasis in a lymph node >6 cm in greatest dimension

In clinical evaluation, the actual size of the nodal mass should be measured and allowance should be made for intervening soft tissues. Most masses >3 cm in diameter are not single nodes but are confluent nodes or tumors in soft tissues of the neck. The 3 stages of clinically positive nodes are: N1, N2, and N3. The use of subgroups a, b, and c is not required but is recommended. Midline nodes are considered homolateral nodes.

Distant metastasis (M)

• MX: Distant metastasis cannot be assessed
• M0: No distant metastasis
• M1: Distant metastasis

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