Stage IV includes: IVA: (T4, N0-2, M0); (Any T, N3, M0); IVB: (Any T, Any N, M1). T4: Tumor invades adjacent structures. N0: No regional lymph node metastasis. N1: Tumor with metastasis in one or two regional lymph nodes. N2: Tumor with metastasis in three to six regional lymph nodes. N3: Tumor with metastasis in seven or more regional lymph nodes. M0: No distant metastasis. M1: Distant metastasis. (AJCC 8th ed.) [from
NCI]