What Is Hodgkin Lymphoma

What Is Hodgkin Lymphoma?
Cancer starts when cells start to grow out of control. Cells in nearly any part of the body can become cancer, and can then spread to other parts of the body. To learn more about how cancers start and spread, see What Is Cancer?

Lymphomas are cancers that start in white blood cells called lymphocytes. There are 2 main types of lymphoma:

Hodgkin lymphoma (HL)
Non-Hodgkin lymphoma (NHL)
They behave, spread, and respond to treatment differently, so it's important for you to know which one you have.

This information is about Hodgkin lymphoma. To learn about the other type, see Non-Hodgkin Lymphoma.

The lymph system
To understand what Hodgkin lymphoma is, it helps to know about the lymph system (also known as the lymphatic system). The lymph system is part of the immune system, which helps fight infections and some other diseases. The lymph system also helps control the flow of fluids in the body.

The lymph system is made up mainly of cells called lymphocytes, a type of white blood cell. There are 2 main types of lymphocytes:

B lymphocytes (B cells): B cells make proteins called antibodies to help protect the body from germs (bacteria and viruses).
T lymphocytes (T cells): There are many types of T cells. Some T cells destroy germs or abnormal cells in the body. Other T cells help boost or slow the activity of other immune system cells.
Hodgkin lymphoma usually starts in B lymphocytes.

Start and spread of Hodgkin lymphoma
Lymph tissue is in many parts of your body, so Hodgkin lymphoma can start almost anywhere.


Illustration showing the lymphatic system in the body
The major sites of lymphoid tissue are:

Lymph nodes: Lymph nodes are bean-sized collections of lymphocytes and other immune system cells. They're found throughout the body, including inside the chest, abdomen (belly), and pelvis. They're connected to each other by a system of lymphatic vessels.

Lymph vessels: A network of tiny tubes (a lot like blood vessels) that connect lymph nodes and carry immune cells in a clear fluid called lymph. Lymph is collected from around the body and put into the bloodstream.

Spleen: The spleen is an organ that's under the lower ribs on your left side. The spleen is part of your immune system. It makes lymphocytes and other immune system cells. It also stores healthy blood cells and filters out damaged blood cells, bacteria, and cell waste.

Bone marrow: The bone marrow is the liquid, spongy tissue inside certain bones. New blood cells (including some lymphocytes) are made there.

Thymus: The thymus is a small organ behind the upper part of the breastbone and in front of the heart. It's important for T lymphocyte development.

Adenoids and tonsils: These are collections of lymph tissue in the back of your throat. They help make antibodies against germs that are breathed in or swallowed.

Digestive tract: The stomach, intestines, and many other organs also have lymph tissue.

Although Hodgkin lymphoma can start almost anywhe