What is Lymphoma?
Lymphoma is a type of cancer involving cells of the immune system, called lymphocytes. Just as cancer represents many different diseases, lymphoma represents many different cancers of lymphocytes — about 35 different subtypes, in fact.
Lymphoma is a group of cancers that affect the cells that play a role in the immune system and primarily represents cells involved in the lymphatic system of the body.
The lymphatic system is part of the immune system. It consists of a network of vessels that carry a fluid called lymph, similar to the way that the network of blood vessels carry blood throughout the body. Lymph contains white blood cells called lymphocytes. Lymphocytes attack a variety of infectious agents as well as many cells in the precancerous stages of development.
Lymph nodes are small collections of lymph tissue that occur throughout the body. The lymphatic system involves lymphatic channels that connect thousands of lymph nodes scattered throughout the body. Lymph flows through the lymph nodes, as well as through other lymphatic tissues including the spleen, the tonsils, the bone marrow, and the thymus gland.
These lymph nodes filter the lymph, which may carry bacteria, viruses, or other microbes. The lymph nodes, or glands as they may be called, filter the lymph, which may on various occasions carry different microbial organisms. At infection sites, large numbers of these microbial organisms collect in the regional lymph nodes and produce the swelling and tenderness typical of a localized infection. These enlarged and occasionally confluent collections of lymph nodes (so-called lymphadenopathy) are often referred to as “swollen glands.” In some areas of the body (such as the anterior part of the neck), they are often visible when swollen.
Lymphocytes recognize infectious organisms and abnormal cells and destroy them. There are two major subtypes of lymphocytes: B lymphocytes and T lymphocytes, also referred to as B cells and T cells.
B lymphocytes produce antibodies (proteins that circulate through the blood and lymph and attach to infectious organisms and abnormal cells). Antibodies essentially alert other cells of the immune system to recognize and destroy these intruders, also known as pathogens.
T cells, when activated, can kill pathogens directly. T cells also play a part in the mechanisms of immune system control, to prevent the system from inappropriate overactivity or underactivity.
After fighting off an invader, some of the B and T lymphocytes “remember” the invader and are prepared to fight it off if it returns.
Cancer occurs when normal cells undergo a transformation whereby they grow and multiply uncontrollably. Lymphoma is a malignant transformation of either B or T cells or their subtypes.
As the abnormal cells multiply, they may collect in one or more lymph nodes or in other lymph tissues such as the spleen.
As the cells continue to multiply, they form a mass often referred to as a tumor. Tumors often overwhelm surrounding tissues by invading their space, thereby depriving them of the necessary oxygen and nutrients needed to survive and function normally. In lymphoma, abnormal lymphocytes travel from one lymph node to the next, and sometimes to remote organs, via the lymphatic system.
While lymphomas are often confined to lymph nodes and other lymphatic tissue, they can spread to other types of tissue almost anywhere in the body. Lymphoma development outside of lymphatic tissue is called extranodal disease.