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 in the organ or tissue that makes it. 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): 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 from the spinal column. This is done by placing a needle into the spinal column. This procedure is also called an LP or spinal tap. A pathologist views the cerebrospinal fluid under a microscope to look for signs of cancer.
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  Lumbar puncture. A patient lies in a curled position on a table. After a small area on the lower back is numbed, a spinal needle (a long, thin needle) is inserted into the lower part of the spinal column to remove cerebrospinal fluid (CSF, shown in blue). The fluid may be sent to a laboratory for testing.

There are three ways that cancer spreads in the body.

The three ways that cancer spreads in the body are:

• Through tissue. Cancer invades the surrounding normal tissue.
• Through the lymph system. Cancer invades the lymph system and travels through the lymph vessels to other places in the body.
• Through the blood. Cancer invades the veins and capillaries and travels through the blood to other places in the body.

When cancer cells break away from the primary (original) tumor and travel through the lymph or blood to other places in the body, another (secondary) tumor may form. This process is called metastasis. The secondary (metastatic) tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the bones, the cancer cells in the bones are actually breast cancer cells. The disease is metastatic breast cancer, not bone cancer.

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

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Stage I AIDS-related lymphoma. Cancer is found in one lymphatic area (lymph nodes, tonsils, thymus, or spleen). In stage IE (not shown), cancer is found in one organ or area outside the lymph nodes.

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.

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  Stage II AIDS-related lymphoma. Cancer is found in two or more lymph node groups, and both are either above (a) or below (b) the diaphragm.
  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).
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  Stage IIE AIDS-related lymphoma. Cancer is found in one or more lymph node groups either above or below the diaphragm and outside the lymph nodes in an organ or area on the same side of the diaphragm as the lymph nodes with cancer (a).
  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

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Stage III AIDS-related lymphoma. Cancer is found in one or more lymph node groups above and below the diaphragm (a). In 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 (b). In stage IIIS, cancer is found in lymph node groups above and below the diaphragm (a) and in the spleen (c). In stage IIIE plus S, cancer is found in lymph node groups above and below the diaphragm, outside the lymph nodes in a nearby organ or area (b), and in the spleen (c).

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

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Stage IV AIDS-related lymphoma. Cancer is found throughout one or more organs that are not part of a lymphatic area (lymph nodes, tonsils, thymus, or spleen) (a); or in one organ that is not part of a lymphatic area and has spread to lymph nodes far away from that organ (b); or cerebrospinal fluid (not shown), the liver, bone marrow, or lungs.

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 lymph nodes or other organs of the lymph system is called peripheral/systemic lymphoma. The lymphoma may spread throughout the body, including to the brain or bone marrow.

Primary CNS lymphoma

Primary CNS lymphoma starts in the central nervous system (brain and spinal cord). Lymphoma that starts somewhere else in the body and spreads to the central nervous system is not primary CNS lymphoma.