Lymphoma is a cancer of the lymphatic system - the system that helps the body fight infection. It's similar to but different from leukaemia, where the problem is cancer of cells in the blood system.
Lymphoma accounts for one in ten childhood cancers, affecting up to three children per 100,000. Non-Hodgkin's is slightly more common than Hodgkin's, but both types are very rare in children under three years. Boys are affected slightly more often than girls.
As recently as 1950, lymphoma was almost always fatal, but these days up to 95 per cent of those newly diagnosed with Hodgkin's lymphoma can expect to be cured. NHL is less easily treated: about 77 per cent of children are still alive five years after diagnosis.
The lymphatic system is made up of thin tubes called lymph vessels that run throughout the body, often alongside blood vessels. These vessels carry lymph, a colourless, watery fluid that contains white blood cells called lymphocytes.
Dotted along the network of lymph vessels are groups of small, bean-shaped lumps called lymph nodes or glands. Clusters of lymph nodes are found under your arms, around your neck and under your chin, and throughout the pelvis, groin, abdomen and chest.
The nodes make and store infection-fighting cells, especially lymphocytes. It's these lymphocytes that become cancer cells in lymphoma.
Lymphoma can start in almost any part of the lymphatic system, then spread to almost any other part of the body including the liver, bone marrow (the spongy tissue inside the large bones of the body that makes blood cells) and the spleen (an organ in the upper abdomen that makes lymphocytes and filters old blood cells from the blood).
· painless swelling of the lymph nodes
· fever for which no cause can be found
· fatigue or extreme tiredness
· night sweats (usually a sign of Hodgkin's)
· weight loss
Often, lymphoma spreads throughout the body before a person is aware that they have a problem.
The exact cause of lymphoma isn't yet known, but there's an inherited tendency and brothers or sisters of a child with lymphoma are slightly more likely than average to get it too.
But this genetic tendency alone isn't enough to trigger the disease - there have to be other aggravating factors. It's suspected that infection with viruses and bacteria can predispose to lymphoma.
People with HIV or Epstein-Barr virus, or those taking immunosuppressive drugs (such as patients who've had kidney or lung transplants) are at greater risk of getting some types of lymphoma. About 30 per cent of all AIDS patients contract it, for example. Alternatively, there may be an environmental factor, such as exposure to pesticides.
It's important to get an exact diagnosis. Slightly different types of white blood cell are involved in Hodgkin's and non-Hodgkin's lymphoma, and the exact type of cancer is determined mainly by what the cells look like under a microscope.
It's important for doctors to find out exactly which type of lymphoma is involved as they need slightly different treatments and have different prognoses or cure rates.
Doctors will also 'stage' the cancer - this means working out how far it has spread around the body.
Lymphomas are usually treated with a combination of chemotherapy, radiation, surgery and bone-marrow transplants. The cure rate varies greatly depending on the type of lymphoma and the progression of the disease, as well as how healthy the child is generally.
· Chemotherapy drugs are used to kill cancer cells and shrink tumours.
· Radiotherapy involves the use of high-energy x-rays to kill the cancer cells.
· Bone marrow transplantation is a newer type of treatment, which allows very high doses of anti-cancer drugs to be given.
Many children with lymphoma will be offered the chance to be treated as part of a clinical trial. While they or their families may be frightened by the idea that they're being used as some sort of guinea pig, they should be very carefully monitored by doctors during the trial. Trials are the only way to find better treatments.
Lymphoma Information Network
This article was last medically reviewed by Dr Trisha Macnair in October 2006.
First published in February 1999.