The lymph system helps control the flow of fluids in the body and is part of the immune system. The lymph system consists mainly of a type of white blood cell called lymphocytes—there are two main types:
- T lymphocytes (T cells). There are many types of T cells. Some T cells destroy germs or abnormal cells in the body, while other T cells help boost or slow the activity of other immune system cells.
- B lymphocytes (B cells). They make proteins called antibodies that help protect the body from bacteria and viruses. Hodgkin lymphoma usually starts in B cells.
Lymph tissue is in many parts of your body, so Hodgkin lymphoma can start almost anywhere.
Major sites of lymphoid tissue
- 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 anywhere, most often it starts in lymph nodes in the upper part of the body. The most common sites are in the chest, neck, or under the arms.
Hodgkin lymphoma most often spreads through the lymph vessels from lymph node to lymph node. Rarely, late in the disease, it can invade the bloodstream and spread to other parts of the body, such as the liver, lungs, and/or bone marrow.