Lymphoma is a cancer that begins in the lymphocytes, which are a type of white blood cell that forms part of the body’s immune system. These cells are distributed throughout the lymphatic system, including the lymph nodes, spleen, thymus, and bone marrow. Staging is the method doctors use to determine how far the lymphoma has spread from its original site within the body, which is a process separate from identifying the specific type of lymphoma. This classification of the disease’s extent is a fundamental step in guiding treatment decisions and predicting a patient’s outlook.
Understanding How Lymphoma is Staged
Lymphoma is staged using the Lugano Classification, which is based on the older Ann Arbor system. This staging system relies primarily on the location and number of affected lymph node areas. The diaphragm, the large muscle separating the chest from the abdomen, serves as a crucial anatomical boundary in this classification.
Doctors determine the stage by conducting various tests, including imaging scans like PET and CT scans, and sometimes a bone marrow biopsy, to map the tumor’s distribution. The classification divides the body into two regions—above and below the diaphragm—to define the anatomical spread of the disease. The resulting stage number provides a common language for medical professionals to describe the disease’s reach and plan treatment.
The Four Primary Stages (I through IV)
Stage I
Stage I is defined by the disease being confined to a single anatomical region. This means the cancer is found in only one lymph node area or a single lymphoid organ, such as the tonsils or thymus. If the cancer is localized to one area of a single organ outside of the lymphatic system, it is also classified as Stage I, specifically Stage IE.
Stage II
Stage II indicates the cancer has spread to two or more lymph node regions, but all affected areas must be situated on the same side of the diaphragm. For instance, the disease might be found in both the neck and armpit lymph nodes, as both are above the diaphragm. Stage IIE describes a situation where the lymphoma involves a single organ outside the lymph system and also affects one or more lymph node regions, provided all affected areas remain on the same side of the diaphragm.
Stage III
Stage III is defined by the involvement of lymph node regions on both sides of the diaphragm. This means that at least one affected lymph node area is located above the diaphragm, and at least one other area is located below it. Stage III may also include localized involvement of an organ next to the lymph nodes, or spread to the spleen, which is considered part of the lymphatic system.
Stage IV
Stage IV is the most advanced classification, defined by the widespread involvement of one or more organs outside the lymphatic system. This generally includes diffuse spread to non-lymphatic sites such as the bone marrow, liver, or lungs. The designation of Stage IV is assigned when the lymphoma has disseminated throughout the body, affecting multiple distant sites beyond the primary lymph node regions.
Modifying Factors That Refine the Stage
The numerical stage (I through IV) is often followed by letters that provide additional, context-specific details about the patient’s condition. The most commonly used modifiers are the “A” and “B” designations, which relate to systemic symptoms experienced by the patient.
A stage followed by the letter “A” indicates the absence of specific systemic symptoms, while the letter “B” signifies their presence. These “B symptoms” include unexplained fevers, drenching night sweats, or unexplained weight loss of more than ten percent of the body weight over the previous six months. The presence of B symptoms suggests a more active disease state and can influence the choice of therapy.
Another important modifier is the letter “E,” which stands for extranodal involvement, meaning the cancer has spread outside the lymph nodes into adjacent or distant organs or tissues. A stage I or II lymphoma may have an “E” modifier if it has spread from a lymph node area into a nearby organ. The letter “S” may be used to denote the involvement of the spleen.