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Non-Hodgkin lymphoma

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What is non-Hodgkin lymphoma?

Non-Hodgkin lymphoma (NHL) is a cancer that starts in lymphocytes. Lymphocytes are cells of the lymphatic system.

The lymphatic system works with other parts of your immune system to help your body fight infection and disease. The lymphatic system is made up of a network of lymph vessels, lymph nodes and the lymphatic organs. Lymph vessels carry lymph fluid, which contains lymphocytes and other white blood cells, antibodies and nutrients. Lymph nodes sit along the lymph vessels and filter lymph fluid. The lymphatic organs include the spleen, thymus, adenoids, tonsils and bone marrow.

Lymphocytes develop in the bone marrow from basic cells called stem cells. Stem cells develop into different types of cells that have different jobs. Lymphocytes are types of white blood cells that help fight infection. There are 2 types of lymphocytes:

  • B cells stay in the bone marrow until they mature.
  • T cells move to the thymus to mature.

Lymphocytes sometimes change and no longer grow or behave normally. These abnormal cells can form tumours called lymphomas. Non-Hodgkin lymphoma can start from either B cells or T cells.

There are over 30 types of non-Hodgkin lymphoma. They are grouped based on the type of lymphocyte they started from. Most types of NHL start in B cells and are called B-cell lymphoma. NHL can also start in T cells, which is called T-cell lymphoma. The different types of NHL look different under a microscope. They also develop and grow differently. The grade of NHL is based on how different, or abnormal, the cancer cells look compared to normal lymphocytes. The grade gives doctors an idea of how slowly or quickly the lymphoma will likely grow and spread. NHL is usually divided into 2 groups:

  • low-grade, or indolent, lymphoma
  • high-grade, or aggressive, lymphoma

Because lymphocytes are found throughout the lymphatic system, NHL can start almost anywhere in the body. It usually starts in a group of lymph nodes in one part of the body, such as in the neck, above the collarbone, under the arms, in the abdomen or in the groin. Unlike Hodgkin lymphoma, which usually spreads in a predictable, orderly way from one group of lymph nodes to the next, NHL doesn’t spread in a predictable way. NHL can spread to almost any tissue or organ in the body through the lymphatic system or the bloodstream.

Other cancers of the lymphatic system are called Hodgkin lymphoma (HL). The abnormal B cells of Hodgkin lymphoma look and behave differently from non-Hodgkin lymphoma cells. Hodgkin lymphomas and non-Hodgkin lymphomas are treated differently.

Diagram of the lymphatic system

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