This is a medical question of type : stages 
 What are the stages of AIDS-Related Lymphoma ? 
 Key Points
                    - After AIDS-related lymphoma has been diagnosed, tests are done to find out if cancer cells have spread within the lymph system or to other parts of the body.     - There are three ways that cancer spreads in the body.    - Stages of AIDS-related lymphoma may include E and S.    - The following stages are used for AIDS-related lymphoma:         - Stage I     - Stage II     - Stage III     - Stage IV        - For treatment, AIDS-related lymphomas are grouped based on where they started in the body, as follows:         - Peripheral/systemic lymphoma     - Primary CNS lymphoma
                
                
                    After AIDS-related lymphoma has been diagnosed, tests are done to find out if cancer cells have spread within the lymph system or to other parts of the body.
                    The process used to find out if cancer cells have spread within the lymph system or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment, but AIDS-related lymphoma is usually advanced when it is diagnosed.    The following tests and procedures may be used in the staging process:         -   Blood chemistry studies : A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease. The blood sample will be checked for the level of LDH (lactate dehydrogenase).     -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the lung, lymph nodes, and liver, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.    -   PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.    -   MRI (magnetic resonance imaging) with gadolinium : A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. A substance called gadolinium is injected into the patient through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   Lumbar puncture : A procedure used to collect cerebrospinal fluid (CSF) from the spinal column. This is done by placing a needle between two bones in the spine and into the CSF around the spinal cord and removing a sample of the fluid. The sample of CSF is checked under a microscope for signs that the cancer has spread to the brain and spinal cord. The sample may also be checked for Epstein-Barr virus. This procedure is also called an LP or spinal tap.
                
                
                    There are three ways that cancer spreads in the body.
                    Cancer can spread through tissue, the lymph system, and the blood:         - Tissue. The cancer spreads from where it began by growing into nearby areas.     - Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.     - Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.
                
                
                    Stages of AIDS-related lymphoma may include E and S.
                    AIDS-related lymphoma may be described as follows:         - E: "E" stands for extranodal and means the cancer is found in an area or organ other than the lymph nodes or has spread to tissues beyond, but near, the major lymphatic areas.    - S: "S" stands for spleen and means the cancer is found in the spleen.
                
                
                    The following stages are used for AIDS-related lymphoma:
                    Stage I      Stage I AIDS-related lymphoma is divided into stage I and stage IE.             -  Stage I: Cancer is found in one lymphatic area (lymph node group, tonsils and nearby tissue, thymus, or spleen).     -  Stage IE: Cancer is found in one organ or area outside the lymph nodes.              Stage II     Stage II AIDS-related lymphoma is divided into stage II and stage IIE.             -  Stage II: Cancer is found in two or more lymph node groups either above or below the diaphragm (the thin muscle below the lungs that helps breathing and separates the chest from the abdomen).     -  Stage IIE: Cancer is found in one or more lymph node groups either above or below the diaphragm. Cancer is also found outside the lymph nodes in one organ or area on the same side of the diaphragm as the affected lymph nodes.              Stage III      Stage III AIDS-related lymphoma is divided into stage III, stage IIIE, stage IIIS, and stage IIIE+S.             -  Stage III: Cancer is found in lymph node groups above and below the diaphragm (the thin muscle below the lungs that helps breathing and separates the chest from the abdomen).     -  Stage IIIE: Cancer is found in lymph node groups above and below the diaphragm and outside the lymph nodes in a nearby organ or area.     -  Stage IIIS: Cancer is found in lymph node groups above and below the diaphragm, and in the spleen.     -  Stage IIIE+S: Cancer is found in lymph node groups above and below the diaphragm, outside the lymph nodes in a nearby organ or area, and in the spleen.              Stage IV     In stage IV AIDS-related lymphoma, the cancer:             - is found throughout one or more organs that are not part of a lymphatic area (lymph node group, tonsils and nearby tissue, thymus, or spleen) and may be in lymph nodes near those organs; or     - is found in one organ that is not part of a lymphatic area and has spread to organs or lymph nodes far away from that organ; or     - is found in the liver, bone marrow, cerebrospinal fluid (CSF), or lungs (other than cancer that has spread to the lungs from nearby areas).           Patients who are infected with the Epstein-Barr virus or whose AIDS-related lymphoma affects the bone marrow have an increased risk of the cancer spreading to the central nervous system (CNS).
                
                
                    For treatment, AIDS-related lymphomas are grouped based on where they started in the body, as follows:
                    Peripheral/systemic lymphoma     Lymphoma that starts in the lymph system or elsewhere in the body, other than the brain, is called peripheral/systemic lymphoma. It may spread throughout the body, including to the brain or bone marrow. It is often diagnosed in an advanced stage.        Primary CNS lymphoma     Primary CNS lymphoma starts in the central nervous system (brain and spinal cord). It is linked to the Epstein-Barr virus. Lymphoma that starts somewhere else in the body and spreads to the central nervous system is not primary CNS lymphoma.