NCIt definition : Stage IVB includes: (T4b, Any N, M0); (Any T, N3, M0). T4b: Tumor with very advanced
local disease. Tumor invades prevertebral fascia, encases carotid artery, or involves
mediastinal structures. N3: Metastasis in a lymph node more than 6 cm in greatest
dimension. M0: No distant metastasis. (AJCC 7th ed.);