Lymphomas are cancers that affect the lymphatic system. The lymphatic system is part of the body’s immune system. It includes tissues such as the bone marrow, tonsils and spleen, as well as lymphatic vessels and lymph nodes. Lymphatic vessels are tiny vessels that collect waste products from the body’s tissues in fluid called lymph. Lymph contains white blood cells including cells called lymphocytes. Lymphocytes help protect the body against infections. Lymph nodes store white blood cells and help to filter out waste products.
Lymphoma arises when developing lymphocytes (a type of white blood cell) undergo a malignant change and multiply in an uncontrolled way. Increasing numbers of abnormal lymphocytes, called lymphoma cells accumulate and form collections of cancer cells called tumours in lymph nodes (glands) and other parts of the body. Over time, lymphoma cells replace normal lymphocytes, weakening the immune system’s ability to fight infection.
There are two main types of lymphoma: Hodgkin lymphoma and non-Hodgkin lymphoma.
Hodgkin lymphoma (HL) is distinguished from other types of lymphoma by the presence of abnormal cells known as Hodgkin or Reed Sternberg cells. About 10% of all lymphomas are HL.
Non-Hodgkin lymphoma (NHL) is the name for any type of lymphoma that does not contain Reed Sternberg cells.