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Approved by the Cancer.Net Editorial Board, 11/2022

About the lymphatic system

The lymphatic system is made up of thin tubes and groups of small, bean-shaped organs called lymph nodes that are located throughout the body. The largest clusters of lymph nodes are found in the abdomen, groin, pelvis, chest, underarms, and neck.

The lymphatic system carries lymph, a colorless fluid that contains a type of white blood cell called a lymphocyte. Lymphocytes are part of the immune system and help fight germs in the body. Types of lymphocytes include:

  • B-lymphocytes, also called B cells, which make antibodies that fight bacteria and other infections
  • T-lymphocytes, also called T cells, which destroy viruses and foreign cells and trigger the B cells to make antibodies
  • Natural killer cells (NK cells), which destroy certain invaders, such as viruses, cells infected by viruses, and some cancer cells

Other parts of the lymphatic system include:

  • Spleen, an organ under the left rib cage, which makes lymphocytes and filters the blood
  • Thymus, an organ under the breastbone
  • Tonsils, located in the throat
  • Bone marrow, the spongy red tissue inside bones that makes:
    • White blood cells, which fight infection
    • Red blood cells, which carry oxygen throughout the body
    • Platelets, which help the blood clot

About non-Hodgkin lymphoma

Lymphoma is a cancer of the lymphatic system. Lymphoma begins when healthy B cells, T cells, or NK cells in the lymphatic system change and grow out of control, which may form a tumor.

Hodgkin lymphoma is a specific type of lymphoma that is covered in another section of this website. Non-Hodgkin lymphoma (NHL) is a term that refers to a group of cancers of the lymphatic system. These cancers can have different symptoms and signs, findings on a physical examination, and treatments.

Because lymphatic tissue is found in most parts of the body, NHL can start almost anywhere and can spread, or metastasize, to almost any organ. It often begins in the lymph nodes, liver, spleen, or bone marrow. However, it can also involve the stomach, intestines, skin, thyroid gland, brain, or any other part of the body.

It is very important to know which type and subtype of lymphoma has been diagnosed. That information can help the doctor figure out the best treatment, as well as a patient’s prognosis, which is the chance of recovery. More information can be found in the Subtypes section of this guide.

This guide covers NHL in adults. A different guide on this website covers childhood NHL.