Hodgkin lymphoma, like other cancers, is a disease of the body's cells. Cells in different parts of the body work in different ways, but they all repair and reproduce themselves in the same way.

Normally, this division of cells takes place in an orderly and controlled manner. However, if for some reason the process gets out of control, the cells continue to divide. Then there may be too many immature white blood cells in the blood or bone marrow. A lump or tumour may then develop in one or more groups of lymph nodes.

Lymphoma cells generally start to grow in lymph nodes (also called lymph glands). Usually, Hodgkin lymphoma affects groups of lymph nodes in one area of the body. However, the lymphoma cells can sometimes spread through the lymphatic system to lymph nodes in other parts of the body.

Lymphoma cells can also go into the bloodstream, which may carry them to other organs. When the cells reach a new area they may go on dividing and form a new tumour.

As there are lymph nodes and lymph vessels throughout the body, Hodgkin lymphoma can start in any part of the body. The most common place for it to start is in the lymph nodes in the neck. The next most common places are the lymph glands:

• under the arms (axilla)
• in the chest
• in the groin
• in the abdomen.

Hodgkin lymphoma can also occur in body organs. In some people it can affect the liver, lungs or bone.

The treatment of Hodgkin lymphoma is usually very successful, even when it has spread to different areas of the body. Most people can now be cured, or the lymphoma can be controlled for many years.