What are lymphomas?

When you or someone you know is diagnosed with lymphoma there will be many questions, uncertainty and perhaps also fear. Many people know little about lymphomas. Lymphoma is a type of cancer, but what sort of cancer?

Lymphoma is also known as lymphatic tissue cancer or cancer of the lymph nodes, which is easier to understand. Lymphoma is a type of cancer that usually develops in lymphatic tissue or in lymph nodes, which are part of the lymphatic system.

Lymphatic tissue is present everywhere in the body. It plays an important role in the body’s defences. Lymphatic tissue contains lymphocyte cells and protects the body against microbes, usually bacteria and viruses, and other harmful substances. Lymphatic tissue involves 500–1,000 lymph nodes that filter a fluid called lymph.

Especially when enlarged, a lymph node can be felt through the skin – it feels like a small bean-shaped lump. Lymph nodes smaller than 1 cm are completely normal and can often be felt, especially if the person is slim.

Lymphoma often attacks lymph nodes and makes them grow in size. It is nevertheless important to remember that other factors, such as infections and inflammations, may make lymph nodes swell temporarily. Such lymph nodes usually return to their normal size within three weeks after the infection has been resolved. A lymph node reacting to an infection – known as a reactive lymph node – often feels rubbery and tender to the touch

Read more about the symptoms of lymphoma.

What is the origin of lymphoma?

Lymphoma often originates in the lymph nodes but may also develop in lymphatic tissue elsewhere in the body. It may thus develop almost anywhere in the body, including the tonsils, spleen, thymus, stomach, intestines, skin, brain or bone marrow.

Cancer develops when an error occurs in the production of lymphocytes, which circulate via the lymph nodes. This results in the formation and division of abnormal cells. Healthy lymphocytes in lymphatic tissue start to turn malignant (cancerous).

Lymphomas are being studied extensively, and treatments are developing, but the origin of the condition is still not fully known. It could, for example, be due to damage to the immune system caused by a viral infection or a bacterium. At present there is no known way to prevent the development of lymphoma.

Frequency and classification of lymphomas

Lymphomas are among the most common cancers in Finland. However, it is difficult to define a uniform profile for the condition. It may develop slowly and go unnoticed or sometimes develop very rapidly. It may develop at a young age or only when a person is older.

Lymphomas are usually classified into two main groups:

  • Non-Hodgkin-lymphoma affects about 1,300 Finns annually. Non-Hodgkin lymphomas are the sixth most common cancer among men (about 700 annually). They are the seventh most common cancer among women.
  • Hodgkin lymphoma is far less common. Approximately 170 Finns develop it annually.

Non-Hodgkin lymphomas are classified into B-cell lymphomas and T-cell lymphomas depending on the type of lymphocyte at the origin of the cancer. B-cell lymphomas are much more common than T-cell lymphomas.

Lymphomas are also classified on the basis of their stage, i.e. how far the cancer has spread. The four stages are as follows:

  • Stage I disease only affects one lymph node area.
  • Stage II lymphoma occurs at two different sites but on the same side of the diaphragm.
  • Stage III lymphoma is present both above and below the diaphragm.
  • Stage IV disease also affects the bone marrow or an internal organ.

Stages III and IV are considered advanced stages of the disease. The prognosis is usually better if the lymphoma only affects lymph nodes locally.

Read more on how lymphomas are diagnosed.