Chapter 084. Head and Neck Cancer (Part 3) Table 84- 1 TNM Classification for Head and Neck Cancer (Except Nasopharyngeal) Primary Tumor Site T Grade Oropharynx Hypopharynx T1 0–2 cm 0–2 cm T2 2.1–4 cm >1 site, 2–4 cm T3 >4 cm >4 cm T4a Lary nx, muscle of tongue, Thyroid/cricoid cartilage, medial pterygoid, hard palate, mandible invasion hyoid bone, thyroid gland, esophagus, or central compartment soft tissue invasion T4b Lateral pterygoid muscle, pterygoid plates, lateral nasopharynx, or sku ll base or encases carotid artery invasion Invasion of prevertebral fascia, encases carotid artery, or involves mediastinal structures Regional Lymph Nodes (N) NX Regional lymph nodes cannot be assessed N0 No regional lymph node metastasis N1 Unilateral metastasis in lymph node(s), ≤6 cm in greatest dimension, above the supraclavicular fossa N2 Bilateral metastasis in lymph node(s), ≤6 cm in greatest dimension, above the supraclavicular fossa N3 Metastasis in a lymph node(s) >6 cm and/or to supraclavicular fossa N3a > 6 cm N3b Extension to the supraclavicular fossa MX Distant metastasis cannot be assessed M0 No distant metastasis M1 Distant metastasis Stage Grouping 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 . Chapter 084. Head and Neck Cancer (Part 3) Table 84- 1 TNM Classification for Head and Neck Cancer (Except Nasopharyngeal) Primary Tumor. muscle of tongue, Thyroid/cricoid cartilage, medial pterygoid, hard palate, mandible invasion hyoid bone, thyroid gland, esophagus, or central compartment soft tissue invasion T4b Lateral. greatest dimension, above the supraclavicular fossa N3 Metastasis in a lymph node(s) >6 cm and/ or to supraclavicular fossa N3a > 6 cm N3b Extension to the supraclavicular fossa MX