The term lymphoma encompasses more than 50 related types of cancer that develop from cells of the immune system. Lymphomas are divided into two general types: Hodgkin lymphoma (also called Hodgkin's disease) and non-Hodgkin lymphomas. The major types of non-Hodgkin lymphomas are indolent (or low grade) and aggressive.
Many, but not all, lymphomas arise from lymphocytes — critical cells in the immune system that originate in the lymph nodes, bone marrow, and thymus, a small organ in front of the heart. These cells circulate in the blood and lymph and live in the lymph nodes and other organs of the lymphatic system — the spleen, thymus, tonsils, and bone marrow. Lymphoma occurs when one of these cells undergoes a transformation into a malignant, or cancerous, cell and begins to grow abnormally, dividing and forming tumors.
Approximately 75,000 people in the United States are diagnosed with lymphoma every year. Combined, non-Hodgkin lymphomas are much more common than Hodgkin lymphoma. Since the early 1970s, the number of new cases of non-Hodgkin lymphomas has doubled in the United States. The greatest increase has occurred among the elderly. Only rates of lung cancer in women and melanoma in the general population have increased more rapidly. Over the same period, the incidence of Hodgkin lymphoma has declined — particularly among the elderly.
Many people live with a low-grade or indolent lymphoma as a chronic problem for a decade or more before needing treatment.
While lymphoma generally occurs in the absence of specific risk factors, some people have medical problems that place them at higher risk.
People whose immune systems are compromised — as a result of inherited genetic diseases, HIV infection, or immunosuppressive drugs taken after an organ transplant — have a higher than average risk of developing lymphoma.
Certain viruses and bacteria can play a role in initiating the disease. Patients with the Epstein-Barr virus, the human T-cell leukemia/lymphotropic virus (HTLV-1, which is most common in some parts of Japan and in the Caribbean islands), and Helicobacter pylori infections (a bacterial infection that causes stomach ulcers and cancer) are at greater risk of some types of lymphoma.
Non-Hodgkin lymphoma has also been linked to exposure to certain kinds of chemicals, including specific pesticides, solvents, and fertilizers. Herbicides and insecticides have been linked to non-Hodgkin lymphoma in studies of farmers, pesticide applicators, and other occupational groups exposed to high levels of these chemicals. Contamination of drinking water with nitrate, a chemical found in fertilizers, may be associated with an increased risk of non-Hodgkin lymphoma. This may be a particular problem in agricultural areas.
Genetics of Lymphoma
Like some other human cancers, lymphomas sometimes occur in multiple members of the same family. Memorial Sloan-Kettering has been helping to collect and perform genetic sequencing on DNA samples from people in families with a history of lymphoma and other cancers of the lymphoid system. By gathering and analyzing this information, researchers hope to identify new genetic markers that could be used to predict a person's risk for developing lymphoma. The findings of this project may also help to identify new ways of treating lymphoma. This work is being conducted at Memorial Sloan-Kettering in collaboration with colleagues at other cancer centers, including the Dana-Farber Cancer Institute, in Boston.
Lymphoma can begin in lymph nodes almost anywhere in the body, in addition to the marrow and thymus, and symptoms depend on its location.
- If lymphoma develops in lymph nodes close to the skin in the neck, underarms, or groin, patients can experience a persistent, painless swelling of those nodes.
- Lymphoma in the stomach or intestines can cause gastrointestinal bleeding, a feeling of fullness, or abdominal swelling.
- Lymphoma in the central nervous system can cause neurological symptoms such as partial paralysis, seizures, confusion, and memory loss.
- Lymphoma in the chest can cause coughing, shortness of breath, and chest discomfort.
Lymph nodes swell for many reasons, most often as a result of an infection. Physicians often treat a patient who has a persistent swelling with antibiotics. If this treatment does not reduce the swelling, the physician might order a biopsy of the swollen node. Swollen lymph nodes are usually not caused by lymphoma.
Other symptoms of lymphoma include fever, fatigue, night sweats, unexpected weight loss, and itching. A rare symptom of Hodgkin lymphoma is pain when drinking alcohol. Like swollen lymph nodes, these symptoms (except for the last) are associated with a wide range of conditions and illnesses. But if these problems persist, consult a physician.