Primary tumor (T)

• TX: Primary tumor cannot be assessed
• T0: No evidence of primary tumor
• Tis: Carcinoma in situ
• T1: Tumor limited to 1 subsite* of the hypopharynx and ≤2 cm in greatest dimension
• T2: Tumor invades more than 1 subsite* of the hypopharynx or an adjacent site, or measures >2 cm but ≤4 cm in greatest diameter without fixation of hemilarynx
• T3: Tumor measures >4 cm in greatest dimension or with fixation of hemilarynx
• T4a: Tumor invades thyroid/cricoid cartilage, hyoid bone, thyroid gland, esophagus, or central compartment soft tissue, which includes prelaryngeal strap muscles and subcutaneous fat
• T4b: Tumor invades prevertebral fascia, encases carotid artery, or involves mediastinal structures

  *Subsites of the hypopharynx are as follows:

  • Pharyngoesophageal junction (i.e., the postcricoid area), extending from the level of the arytenoid cartilages and connecting folds to the inferior border of the cricoid cartilage.
  • Pyriform sinus, extending from the pharyngoepiglottic fold to the upper end of the esophagus, bounded laterally by the thyroid cartilage and medially by the surface of the aryepiglottic fold and the arytenoid and cricoid cartilages.
  • Posterior pharyngeal wall, extending from the level of the floor of the vallecula to the level of the cricoarytenoid joints.

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 greatest 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 centimeters in diameter are not single nodes but confluent nodes or tumors in soft tissues of the neck. There are 3 stages of clinically positive nodes: N1, N2, and N3. The use of subgroups a, b, and c is not required but 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

• T4b, any N, M0
• Any T, N3, M0

Stage IVC

• Any T, any N, M1