The staging system used for non-Hodgkin's lymphomas is the Ann Arbor convention developed for the staging and treatment (primarily with radiation) of Hodgkin's disease.
Sometimes a distinction has been made between "clinical" and "pathologic" staging. Clinical staging describes the apparent stage of the disease as determined by physical examination, x-rays and blood tests. Pathologic staging has generally involved exploratory abdominal surgery (laparotomy) to assess lymph nodes , the liver and spleen for lymphoma. Laparotomy cannot now be recommended for staging of NHL. Strictly speaking, biopsy of the bone marrow is pathologic staging, but the procedure is commonly included as part of clinical staging.
Stage I Involvement of a single lymph node region (Stage I) or localized involvement of a single organ or site other than lymph nodes (IE).
Stage II Involvement of two or more lymph node regions on the same side of the diaphragm (either above or below the breathing muscle separating the chest from the abdomen) (Stage II) or localized involvement of a single associated organ or site other than lymph nodes (extralymphatic) and its regional lymph nodes, with or without other lymph node regions on the same side of the diaphragm (IIE).
