Set cell lymphoma is classified as stage IV. Stage I means that the set cell lymphoma is limited to only 1 lymph node area. In stage II, there are 2 or more lymph node areas, but they are all confined to the same side of the septum. If lymph node involvement occurs on both sides of the septum, it is stage III of lymphoma. If there is visceral metastasis or invasion of lungs, liver, bone, bone marrow, etc., it belongs to stage IV of lymphoma. Stages I and II are early-stage lymphoma, while stages III and IV are advanced-stage lymphoma. Most of the lymphomas are highly malignant tumors, while a few intranodal NK/T-cell lymphomas are less malignant tumors, and the treatment should be chosen according to the stage.