Diagnosing AIDS-related lymphoma is generally done quite late, after the disease has already advanced. In order to see whether the disease has spread within the lymph system or to other organs, doctors need to perform a procedure called staging that will finally determine the evolution stage of the disease. Knowing all these facts, the doctor can advice the patient what treatment to follow.

One of the tests made to determine the stage of the lymphoma is the CT (computer tomography) an X-ray based machine that will show detailed image of your organs and other related structures to them. You could be advised to take some oral drugs or the doctors will give you an injection that contains some dye, which will help them see a clearer image of your lymph system and bloodstream.

Another test is the PET scan which is designed to find the malign tumors inside your body. The substance used to track the tumors is a radionuclide glucose injected in your vein. This substance will brighten the tumor in the picture because the tumor uses the glucose for its development.

MRI (magnetic resonance imaging) is also useful because it takes detailed pictures of your body, using magnet, radio waves. In this case, the substance used to brighten tumors in the picture is gadolinium.

Other reliable tests are the bone marrow biopsy, made on the hipbone or breastbone, and the lumbar puncture that takes some drops of the cerebrospinal fluid from the spinal column which will be analyzed in the laboratory to see if there are any signs of cancer.

AIDS-related lymphoma stages might include the E and S stages.
The E stage stands for extra-nodal meaning that the cancer has not reached the lymph nodes yet and that it is situated in other organs.
The S stage means that the cancer has reached the spleen and affects it.

Stage I of AIDS-related lymphoma is classified as stage I and stage IE; stage I means that the cancer has affected one group of lymph nodes; stage IE means that the cancer has not reached the lymph nodes yet and affects other organs.

Stage II is classified as stage II (cancer has affected two or more lymph node groups on the same side of the diaphragm) and stage IIE (cancer has affected the lymph nodes near the previous affected organs).

Stage III is divided into stage III, stage IIIE, stage IIIS and stage IIIE+S
Stage III - cancer has affected lymph nodes on the both sides of the diaphragm.
Stage IIIE ? besides the lymph node group on the both sides of the diaphragm, cancer is found in other organs too.
Stage IIIS - besides the lymph node group on the both sides of the diaphragm, cancer is found in the spleen too.
Stage IIIE+S - besides the lymph node group on the both sides of the diaphragm, cancer is found in other organs and in the spleen too.

In stage IV the cancer is considered to have attacked multiple organs and associated lymph nodes and also distant lymph node groups.

In AIDS-related lymphoma patients the risk that the cancer will spread towards CNS (central nervous system) is quite high.

In treating the disease, the lymphoma is grouped based on where the cancer started in the organism: if it starts from the lymph nodes is called peripheral lymphoma; if it starts is the CNS is called primary CNS lymphoma.