Stage IVB includes: (Any T, N3, M0); (T4b, Any N, M0). T4b: Very advanced local disease. Tumor invades lateral pterygoid muscle, pterygoid plates, lateral nasopharynx, or skull base or encases carotid artery. N3: Tumor with metastasis in a lymph node larger than 6 cm in greatest dimension and ENE(-); or metastasis in a single ipsilateral lymph node larger than 3 cm in greatest dimension and ENE(+); or metastases in multiple ipsilateral, contralateral, or bilateral lymph nodes any with ENE(+). M0: No distant metastasis. (AJCC 8th ed.) [from NCI]