There are filters at certain points throughout the lymphatic system called lymph nodes, which usually exist in grape-like clusters.

CNN: What is Hodgkin lymphoma's effect on the lymphatic system?

It is a cancer of the lymphatic system, which is a part of the immune system that consists of a series of ducts or tubes that parallel the arteries and veins throughout the body.

CNN: What is Hodgkin lymphoma's effect on the lymphatic system?

Lymphomas are cancers of the lymphatic system, a network of vessels which form part of the body's immune system, and carry other infection-fighting cells called "lymphocytes", as well as draining dead cells away from the tissues.

BBC: The drug targets cancer cells directly