Lymphomas are cancers that develop in the lymph system, which is part of the body's immune system.
Because there is lymph tissue throughout the body, lymphomas can start in almost any part.
The type of lymphoma usually associated with HIV is called non-Hodgkin's lymphoma.
Lymphoma often causes fever and night sweats; other symptoms depend on which area of the body is affected.
Lymphoma may be treated with chemotherapy; lymphoma involving the brain may be treated with radiation therapy.
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What is lymphoma and what causes it?
Lymphomas are cancers that develop in the lymph system, which is part of the body's immune system.
The lymphatic system is made up of thin tubes that branch, like blood vessels, into all parts of the body. Lymph vessels carry lymph, a watery fluid that contains white blood cells called lymphocytes. Along the network of vessels are groups of small, bean-shaped organs called lymph nodes, which make and store infection-fighting cells. Clusters of nodes are found in the underarm, pelvis, neck and abdomen.
The spleen (an organ in the upper abdomen that makes lymphocytes and filters old blood cells from the blood), the thymus (a small organ beneath the breastbone), and the tonsils (an organ in the throat) are also part of the lymph system. Because lymphatic tissue occurs in many parts of the body, lymphomas can start in almost any tissue or organ.
Lymphomas are divided into two general types: Hodgkin's disease and non-Hodgkin's lymphomas. Lymphoma associated with HIV disease is usually non-Hodgkin's lymphoma (NHL).
A normal lymphocyte divides to produce many identical cells in response to certain chemical signals, but it also stops dividing in response to specific chemical control signals. However, if a lymphocyte is damaged so that it does not recognise the control signals to stop cell division, it will eventually produce a mass of cells that divide uncontrollably. This mass of abnormally growing cells is a lymphoma, a tumour that can cause blockages and displace normal cells and tissue. Abnormal lymphocytes may spread to other parts of the body, where they form other tumours.
NHL occurs much more frequently in HIV-infected people than in the general population, and is most often associated with advanced disease. There are two major types of NHL in people with HIV infection:
Lymphoma arising in the brain and spinal cord (primary central nervous system NHL, or primary CNS NHL)
Lymphoma arising in other parts of the body (systemic NHL).
Primary CNS NHL almost always occurs in people with very advanced HIV disease (CD4 cell count below 50/ul), whereas systemic NHL is sometimes seen in people with a higher CD4 count.
Symptoms and signs of lymphoma
Lymphoma often causes fever and night sweats. Further lymphoma symptoms depend on which areas of the body are affected.
Lymphomas commonly involve the lymph nodes, and so may be found where there are clusters of these, such as in the neck, groin or underarm area. Lymphoma may also occur in the brain and spinal cord, digestive tract, bone marrow, liver, mouth and rectum. If lymphoma is present in a lymph node, the node enlarges to form a lump that is usually not painful.
If lymphoma occurs in the brain, symptoms may include confusion, tiredness, memory loss, seizures, speech difficulties, headache, and numbness, tingling or weakness in the limbs.
Swollen lymph nodes do not always indicate the presence of lymphoma. HIV infection itself often causes moderate, non-tender lymph node enlargement (generalised lymphadenopathy syndrome), and other types of infection can also produce enlarged lymph nodes.
How is lymphoma diagnosed?
Your doctor may suspect you have lymphoma if you are experiencing fever or sweats, symptoms indicating a CNS problem, an enlarged lymph node or lymph node cluster, or a mass detected on physical examination.
A radiographic study (CT or MRI scan) of the brain, chest and abdomen may reveal a mass or enlarged lymph nodes that suggest lymphoma.
To prove that a mass is lymphoma requires a biopsy (tissue sample). Sometimes sufficient tissue is obtained by inserting a thin needle into the mass and drawing material into the syringe (fine needle aspiration or FNA). In other cases, the doctor may need to cut a small sample of tissue from the mass with a scalpel, after first providing an anaesthetic.
The sample is then sent to the laboratory and examined for cancerous cells.
If you have symptoms of brain involvement, your doctor may give you medications used to treat toxoplasmosis, an infection seen in people with advanced HIV disease, to see if the tumour is not instead caused by toxoplasmosis. If it does not shrink, CNS NHL could be the cause, and brain biopsy may be necessary to confirm the diagnosis.
How is lymphoma treated?
Effectiveness of treatment depends on the particular cell characteristics of the lymphoma, its location, and how much it has spread, as well as the strength of your immune system.
Systemic NHL is treated with chemotherapy, which consists of several anti-cancer drugs given intravenously (IV) over a period of time. Side-effects from chemotherapy are common. In addition, several drugs may cause a low white blood cell count (neutropenia), which can make you vulnerable to bacterial infections. Neutropenia is preventable by using a medication called granulocyte colony stimulating factor (G-CSF), which helps the bone marrow produce more of these cells.
Primary CNS NHL is much more difficult to treat, and people who have this disease usually do not live more than six months after diagnosis. This is because people with primary CNS NHL have very advanced HIV disease and are at risk for severe infections and other complications. Primary CNS lymphoma is generally treated by radiation of the brain. This may improve symptoms for a few weeks or months, but does not cure the tumour.
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