TNM Definitions
AJCC Stage Groupings

The staging systems are all clinical staging and are based on the best possible estimate of the extent of disease before treatment. The assessment of the primary tumor is based on inspection and palpation when possible and by both indirect mirror examination and direct endoscopy when necessary. The tumor must be confirmed histologically, and any other pathologic data obtained on biopsy may be included. The appropriate nodal drainage areas are examined by careful palpation. Information from diagnostic imaging studies may be used in staging. Magnetic resonance imaging offers an advantage over computed tomographic scans in the detection and localization of head and neck tumors and in the distinction of lymph nodes from blood vessels.[1] If a patient relapses, complete restaging must be done to select the appropriate additional therapy.[2,3]

The American Joint Committee on Cancer (AJCC) has designated staging by TNM classification.[4]

Primary tumor (T)

• TX: Primary tumor cannot be assessed
• T0: No evidence of primary tumor
• Tis: Carcinoma in situ
• T1: Tumor no larger than 2 cm in greatest dimension
• T2: Tumor larger than 2 cm but no larger than 4 cm in greatest dimension
• T3: Tumor larger than 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, no larger than 3 cm in greatest dimension
• N2: Metastasis in a single ipsilateral lymph node, larger than 3 cm but no larger than 6 cm in greatest dimension; or in multiple ipsilateral lymph nodes, no larger than 6 cm in greatest dimension; or in bilateral or contralateral lymph nodes, no larger than 6 cm in greatest dimension
  • N2a: Metastasis in a single ipsilateral lymph node larger than 3 cm but no larger than 6 cm in dimension
  • N2b: Metastasis in multiple ipsilateral lymph nodes, no larger than 6 cm in greatest dimension
  • N2c: Metastasis in bilateral or contralateral lymph nodes, no larger than 6 cm in greatest dimension
• N3: Metastasis in a lymph node larger than 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 larger than 3 cm in diameter are not single nodes but are confluent nodes or tumors in soft tissues of the neck. The three 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

References

1. Consensus conference. Magnetic resonance imaging. JAMA 259 (14): 2132-8, 1988.  [PUBMED Abstract]
   
   
2. Harrison LB, Sessions RB, Hong WK, eds.: Head and Neck Cancer: A Multidisciplinary Approach. Philadelphia, Pa: Lippincott-Raven, 1999. 
   
   
3. Wang CC, ed.: Radiation Therapy for Head and Neck Neoplasms. 3rd ed. New York: Wiley-Liss, 1997. 
   
   
4. Lip and oral cavity. In: American Joint Committee on Cancer.: AJCC Cancer Staging Manual. 6th ed. New York, NY: Springer, 2002, pp 23-32. 
   
   

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