Lymphoma is a cancer of the lymph (or lymphatic) system. It is part of the immune system. It collects and destroys invading organisms, such as bacteria and viruses, and abnormal cells. It protects the body from infection and disease.
The lymph system is a network of tissue, vessels, and fluid (lymph). It includes:
Lymph. This clear fluid carries white blood cells, especially lymphocytes, though the lymph system. White blood cells help fight infection.
Lymph vessels. These thin tubes carry lymph from different parts of the body to the bloodstream.
Lymph nodes. These small masses of tissue store white blood cells. They also help remove bacteria and other substances from the lymph. Lymph nodes are located in the neck, underarms, chest, abdomen, pelvis, and groin.
Lymph tissue also resides in the spleen, thymus gland, tonsils, bone marrow, and digestive system.
Lymphatic tissue is composed mainly of lymphocytes. There are two main types of lymphocytes:
B cells make antibodies that kill bacteria and viruses.
T cells fight infections using other chemicals and processes.
Lymphoma starts when a lymphocyte changes into an abnormal cell that begins dividing out of control. These abnormal cells often form masses (tumors) in lymph nodes and elsewhere. Because lymph tissue is located throughout the body, lymphoma can begin almost anywhere. It can spread to almost any tissue or organ.
The two main types of lymphoma are Hodgkin disease (Hodgkin lymphoma) and non-Hodgkin lymphoma. There are about 30 different types of non-Hodgkin lymphoma.
Hodgkin disease can affect lymph tissue anywhere in the body. It can also spread from lymph tissue to other organs. Hodgkin disease usually affects people in their late 20s or older than 50. Males get the disease more often than females. Whites are affected more often than people of other races.
Most lymphoma is non-Hodgkin lymphoma. In adults, non-Hodgkin lymphoma affects males more than females. It often occurs between the ages of 60 and 70. Whites are affected more often than people of other races.
Non-Hodgkin lymphoma has become more common in the past few decades. This may be related to the rise in the number of people who have a suppressed immune system, such as people infected with human immunodeficiency virus (HIV) and those who have had an organ transplant and need to take drugs that alter the immune system.
Age is a major determinant of the type of non-Hodgkin lymphoma. Slow growing lymphomas (low grade) are more likely to occur in an older person. Fast growing (high grade aggressive) non-Hodgkin lymphomas usually affect children and young adults. Lymphomas are classified by the specific characteristics of the cancer cells and the parts of the body affected.