Lymphoma (lim-FOH-mah) are cancers that are grouped together because they arise in the lymphocytes, a type of white blood cell located within lymph nodes * of the immune system * . Generally, the lymphatic system is the network of vessels that carry the lymph fluid, which contains blood cells, throughout the immune system. Within this system, lymphoma first occurs. Hodgkin lymphoma is one well-known example of lymphoma. Non-Hodgkin lymphoma is sometimes used to refer to all lymphomas other than Hodgkin lymphoma. The scientific classification of lymphoma includes a wide variety of forms: More than 30 types of lymphomas have been identified.
Lymphoma is a general term for a group of cancers that begin in the lymphatic system, which consists of the tissues and organs used to make, store, and carry white blood cells for fighting infections and other diseases. This system includes the bone marrow * , spleen * , and hundreds of bean-sized lymph nodes throughout the body. Lymphoma results when white blood cells, or lymphocytes (LIM-fo-sites), undergo changes and start to multiply out of control. Eventually, the cells crowd out healthy cells and create tumors, which are abnormal growths of body tissue. Tumors may or may not be cancerous. Lymphoma can occur in a single lymph node, a group of lymph nodes, or in other parts of the lymphatic system. Eventually, it may spread to almost any part of the body.
The different types of lymphoma vary in severity, survivability, and frequency. Some types do not occur often. For instance, hairy cell leukemia *
Lymphoma is traditionally classified into two main types: Hodgkin disease, named after British physician Thomas Hodgkin (1798–1866), and non-Hodgkin lymphoma. The two types are distinguished by how the cancer cells look under a microscope and how they behave, multiply, and respond to medical treatment. Within each class many different subtypes have been identified. The World Health Organization (WHO) classification system for the subtypes within each type was established in 2008. It defines subtypes not only by the appearance of the cancer cells and but also where they occur, any chromosome * changes and abnormalities, and the presence or absence of different proteins on the surfaces of the cells. No matter what the type, however, both cancers make a person sick in the same way. Some types of lymphoma are among the most common childhood cancers. Most cases of lymphoma occur in adults.
For non-Hodgkin lymphoma, the major subtypes are distinguished by whether the cancer affects either B cells or T cells and/or natural killer cells. B cells, also called B lymphocytes (in which the letter B stands for bursa of Fabricius, a bird gland where the tissue was first found), are white blood cells that make antibodies * , which are an essential factor in the body's defense against toxins, viruses, and bacteria. In the United States, 85 percent of non-Hodgkin lymphoma cases are B-cell lymphomas.
T cells, also called T lymphocytes (in which the letter T stands for thymus), are another type of white blood cell found within the blood. They protect the body by attacking foreign substances. Diseases can cause damage to T cells. When damaged, T cells degrade (reduce) the body's ability to defend itself against infections. Natural killer cells, a specific type of T cell, have the ability to destroy microbes and tumor cells by releasing small granules. T-cell lymphomas account for fewer than 15 percent of non-Hodgkin lymphomas in the United States. Lymphomas of natural killer cells are even rarer and are considered a kind of T cell lymphoma.
There are numerous subtypes within each type of lymphoma. Within the B-cell tumor group of non-Hodgkin lymphoma, major subtypes include small cell lymphoma (which is found mostly in the lymph nodes), chronic lymphocytic leukemia (bone marrow and blood), and B-cell prolymphocytic leukemia (a severe form of chronic lymphocytic leukemia). Two other B-cell lymphomas are follicular lymphoma (in which the cells contain a vague clustering pattern) and Burkitt's lymphoma (which is associated with Epstein-Barr virus that causes mononucleosis * ).
Classic Hodgkin disease has four major subtypes. They are nodular sclerosis Hodgkin disease (the most common), mixed cellularity Hodgkin disease, lymphocyte-rich Hodgkin disease, and lymphocyte-depleted Hodgkin disease (the rarest subtype). In general, classic Hodgkin disease spreads in regular fashion from lymph node to lymph node through the lymphatic system, is diagnosed early in the disease process, and is eminently treatable. It was one of the first types of cancer to be cured.
As of 2016, exactly what causes lymphoma was unknown. It is not contagious, like a cold or chickenpox. Scientists do know that lymphoma is caused by changes in the genetic coding of a lymphocyte, but most of the time, no one knows why these gene * changes occur. Changes in the DNA * of a gene cause the abnormal coding that leads to normal lymphocytes becoming cancerous. DNA, which is material that people inherit from their parents, carries the instructions for everything the cells do. Just as people get bumps and scrapes during their lifetimes, the genes may also suffer different kinds of damage that cause malfunction. When that happens, coding signals may cause cells to grow out of control and form a tumor. In Burkitt's lymphoma, for instance, cancerous B cells spread into the blood, bone marrow, and central nervous system * .
Oncogenes (on-KO-jeens) can cause cells to grow out of control. They are the result of a normal gene (called a proto-oncogene * ) mutating through cell division and failing to control it in a regular way. Such gene mutations are thought to increase the chances of healthy cells becoming tumorous, which can lead to cancers such as lymphoma. Oncogenes were first discovered in retroviruses * and, later, identified as having a part in the development of cancer.
Oncogenes are a major risk factor for the development of lymphomas, and other risk factors have also been identified, although most people have no known risk factors. (A risk factor is anything that increases a person's chances of getting a disease.) Having AIDS * or an autoimmune disease * , for example, increases the risk for lymphoma.
In addition, certain viruses appear to cause changes in genes that can lead to lymphoma. Epstein-Barr virus * can cause lymphoma in people with weakened immune systems. In people with healthy immune systems, the same virus has been linked to a form of the disease called Burkitt's lymphoma, which occurs in children and adults in Central Africa but is rare in the United States. A virus called HTLV-1 * causes a kind of lymphoma seen almost exclusively in certain geographical areas, particularly Japan, the Caribbean, and the southeastern United States. In most cases doctors have no idea why lymphoma develops.
Some people with lymphoma have early symptoms that cause them to go to the doctor. Others may have no symptoms at all, or they may mistake their symptoms for the flu (influenza) or another ordinary illness. This is because the body responds to lymphoma as though it were an infection. For example, Jacqueline Kennedy Onassis (1929–1994), the widow of President John F. Kennedy (1927–1963), was diagnosed with lymphoma after she went to the doctor thinking she had the flu. John Cullen (b. 1964), a former professional hockey player, experienced his first symptom as a pain in his chest after a game.
Lymphoma is generally characterized by enlarged lymph nodes in one or more parts of the body, such as painless swellings of the lymph nodes in the neck, armpit, chest, or groin. Other common symptoms include night sweats, weight loss, fever, malaise, tiredness, and reddening of the skin. Vomiting and nausea can sometimes occur. In addition, the same physical reaction that causes itchiness in allergic reactions can cause widespread itching in lymphoma. Various other symptoms can eventually occur, depending on where the cancer has spread. For example, lymphoma that has spread into the lungs will cause a cough, whereas abdominal pain usually indicates the cancer has spread into the gastrointestinal * tract.
If lymphoma is suspected, a doctor can order various medical tests, including imaging studies to allow the doctor to see inside the body. Because many of the symptoms of lymphoma can be caused by noncancerous problems such as infections, the only way to be sure that a person has lymphoma is to do a biopsy (BY-op-see). This procedure involves removing a sample of tissue from a lymph node, or sometimes even an entire node, for examination under a microscope. If cancerous cells appear from the microscopic examination, physicians make further investigations in order to learn what type of lymphoma is present.
Specifically, medical professionals determine the stage at which the lymphoma is present in the body by performing such tests as CT scans * and x-rays; ultrasound * tests, MRIs * , and positron emission tomography scans (imaging that shows the performance of tissues and organs); bone marrow biopsies; lumbar puncture tests (drawing of fluid from the lower spine); and a comprehensive set of blood tests, including complete blood count.
Genetic and immunologic studies help to distinguish among the numerous types of lymphoma. A wide range of tests is important to properly assess the spread of lymphoma cells in the body and accurately determine the cell type involved so that the most effective type of treatment can be identified and performed. The clinical analysis usually divides lymphomas into three grades: low, intermediate, and high. The low-grade form is the most survivable form.
Once the doctor knows for sure that a patient has lymphoma, the next step is to determine how much the lymphoma has spread or progressed; this is done with a process called staging. This evaluation involves determining what cell type is involved, whether the cancer has spread, and if so, how far. Staging is essential for deciding what kind of treatment a person with lymphoma should receive and what the outlook for survival is for the patient. The systems used to stage the different types of lymphoma are different, but the goal is always to decide the best treatment for the patient.
Early-stage non-Hodgkin lymphoma (involving B-cell tumors and T-cell/natural-killer-cell tumors) that has not spread is usually treated with radiation therapy, which uses high-energy waves to damage and destroy cancer cells. If the disease is widespread, it will probably require chemotherapy (kee-mo-THER-ah-pee), which uses anticancer drugs that can reach throughout the body to fight cancer cells. Chemotherapy drugs are given either through a vein in the arm or as pills taken orally. Sometimes chemotherapy is combined with radiation. Hodgkin disease is also treated with radiation, chemotherapy, or both.
Both chemotherapy and radiation can have side effects because treatments that kill cancer cells can also affect healthy cells. The most common side effects of chemotherapy are nausea (feeling sick to the stomach), vomiting, hair loss, and tiredness. Nausea and vomiting can be prevented with medication, and, fortunately, most of these side effects go away after the treatment is completed.
Immunotherapy (sometimes called biological therapy) is a treatment that uses parts of the immune system to fight cancer cells, either by stimulating the immune system to attack the cells or with laboratory-made immune system components that are introduced into the patient's body to teach the immune system to recognize and kill the cancer cells. Laboratory-made antibodies, called monoclonal antibodies, are specifically designed to adhere to some kinds of lymphoma cells, signaling other parts of the immune system to help destroy them. Monoclonal antibodies are the most common immunotherapy used against lymphoma, and as of 2016 at least six different monoclonal antibody drugs were available for different types and subtypes of lymphoma.
Targeted therapy drugs are the newer treatment methods available for lymphoma patients, usually used after more standard treatments have been tried. These drugs specifically target the changes in the proteins of the cells that have made them cancerous. One example of such drugs is called a proteasome inhibitor. The drug works by stopping the cells from destroying the proteins that work to keep cell division in control. Another example, called a kinase inhibitor, is particularly beneficial for Mantle cell lymphoma. This drug blocks a protein that sends the cancer cell a signal to grow and multiply. Other targeted therapy drugs are useful for other types of lymphoma.
Sometimes a bone marrow or stem cell * transplant is performed after the use of chemotherapy or radiation. Cancer cells are killed off in the chemotherapy or radiation process, and later, healthy bone marrow or stem cells are introduced back into the body with the use of such transplants.
Unlike several other kinds of cancer, there are no known factors related to lifestyle, such as exposure to sunlight or specific eating habits or smoking habits that a person could change in the hope of lowering the risk of getting lymphoma. However, preventing HIV * (AIDS virus) infection would prevent some cases of non-Hodgkin lymphoma.
Researchers are studying how normal lymphocytes develop into cancer cells. This information may be used one day in gene therapy * to replace abnormal genes with normal ones and allow cells to grow normally again. This same knowledge is also being used to try to detect lymphoma earlier and to test how completely lymphoma is destroyed by treatment. Lymphoma cells sometimes become resistant to chemotherapy: The cancer cells are able to change (mutate) so that the drugs are no longer effective. Various drugs are being studied that could interfere with this resistance so as to make chemotherapy more effective. Both immunotherapy and targeted therapy are rapidly advancing fields of medical research, and in 2016 many immune system-based and targeted drugs were under development. In addition, several vaccines were being tested for efficacy in producing an anticancer immune system response.
Because treatment of both non-Hodgkin lymphoma and Hodgkin disease usually involves chemotherapy and radiation, one of the most difficult parts of living with lymphoma is coping with treatment. Many side effects of chemotherapy and radiation are short term and go away when treatment stops. Other side effects, however, are long term. For example, treatment may affect a person's ability to have children, or it may trigger the development of a different lymphoma many years later.
Follow-up care may continue for years or even decades. Aside from doctor's visits, once all signs of cancer are gone, people can go back to doing whatever they did before they got lymphoma. Most children with childhood lymphoma survive it, and they can expect to lead normal lives as adults.
See also AIDS and HIV • Cancer: Overview • Infection • Leukemia • Radiation Exposure • Tumor
Holman, Peter, and Gregory Bociek. 100 Questions & Answers About Lymphoma, 3rd ed. Burlington, MA: Jones and Bartlett Learning, 2014.
Marcus, Robert, and John W. Sweetenham. Lymphoma: Pathology, Diagnosis, and Treatment, 2nd ed. Cambridge, UK: Cambridge University Press, 2014.
American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: http://www.cancer.org (accessed March 24, 2016).
Lymphoma Research Foundation. 115 Broadway, Suite 1301, New York, NY 10006. Telephone: 212-349-2910. Website: http://www.lymphoma.org (accessed March 24, 2016).
National Cancer Institute. 9609 Medical Center Dr., Bldg. 9609, MSC 9760, Bethesda, MD 20892. Toll-free: 800-422-6237. Website: http://www.cancer.gov (accessed March 24, 2016).
* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* immune system (im-YOON) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* bone marrow is the soft tissue inside bones where blood cells are made.
* spleen is an organ in the upperleft part of the abdomen that stores and filters blood. As part of the immune system, the spleen also plays a role in fighting infection.
* leukemia (loo-KEE-me-uh) is a form of cancer characterized by the body's uncontrolled production of abnormal white blood cells.
* chromosome (KRO muh sohm) is one of 23 pairs of long strands of DNA in the cell that is arranged into groups of genes that control how an organism grows and functions and how the cell behaves.
* antibodies (AN-tih-bah-deez) are protein molecules produced by the body's immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.
* mononucleosis (mah-no-nuklee-O-sis) is an infectious illness caused by a virus with symptoms that typically include fever, sore throat, swollen glands, and tiredness.
* gene is a specific portion of DNA that is the basic unit of heredity; usually located on a chromosome, it codes for a specific trait or function.
* DNA, or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-KLAYik), is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
* central nervous system is the part of the nervous system that includes the brain and spinal cord.
* proto-oncogene (pro-toe-AHNKeh-gene) is a specialized gene that codes for regulating cell growth, stimulating cell division, and controlling cell death.
* retrovirus is a virus in which the genetic information is found in ribonucleic acid (RNA), a nucleic acid that is found in all living cells.
* AIDS, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome, is an infection that severely weakens the immune system. It is caused by the human immunodeficiency virus (HIV).
* autoimmune disease (awtoh-ih-MYOON) is a disease in which the body's immune system attacks some of the body's own normal tissues and cells.
* viruses (VY-rus-sez) are tiny infectious agents that can cause infectious diseases. A virus can only reproduce within the cells it infects.
* Epstein-Barr virus (EP-stineBAHR VI-rus) is a common virus that causes infectious mononucleosis.
* HTLV-1 short for human T-cell lymphotropic virus type 1, is a virus that is associated with certain kinds of adult leukemia and lymphoma.
* gastrointestinal (gas-tro-in-TEStih-nuhl) pertains to the organs of the digestive system, which processes food. The gastrointestinal system includes the mouth, esophagus, stomach, intestines, colon, and rectum and other organs involved in digestion, including the liver and pancreas.
* CT scans, computed tomography (to-MOG-ra-fee) scans, or CAT (computerized axial tomography) scans, use computers to view structures inside the body.
* ultrasound, also called a sonogram, is a diagnostic test in which sound waves passing through the body create images on a computer screen.
* MRI, short for magnetic resonance imaging, produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.
* stem cell is an unspecialized cell that gives rise to differentiated cells.
* HIV or human immunodeficiency virus (ih-myoo-no-dih-FIHshen-see), is the virus that causes AIDS (acquired immunodeficiency syndrome).
* gene therapy is a treatment that works by altering genes.