Stage IV includes: IVA: (T4, N0, M0); (T4, N1, M0); (T4, N2, M0); (Any T, N3, M0); IVB (Any T, Any N, M1). T4: Tumor with intracranial extension, involvement of cranial nerves, hypopharynx, orbit, parotid gland, and/or extensive soft tissue infiltration beyond the lateral surface of the lateral pterygoid muscle. N0: No regional lymph node metastasis. N1: Tumor with unilateral metastasis in cervical lymph node(s), and/or unilateral or bilateral metastasis in retropharyngeal lymph node(s), 6 cm or smaller in greatest dimension, above the caudal border of cricoid cartilage. N2: Tumor with bilateral metastasis in cervical lymph node(s), 6 cm or smaller in greatest dimension, above the caudal border of cricoid cartilage. N3: Tumor with unilateral or bilateral metastasis in cervical lymph node(s), larger than 6 cm in greatest dimension, and/or extension below the caudal border of cricoid cartilage. M0: No distant metastasis. M1: Distant metastasis. (AJCC 8th ed.) [from NCI]