Hodgkin lymphoma, or Hodgkin disease, is named for Thomas Hodgkin, MD, who described it as a new disease in 1832. All other types of lymphoma are grouped as the non-Hodgkin type. The cancer cells must be checked in the lab to know which type it is.

Other types of cancer can spread to the lymphatic system, but lymphomas are the most common type of cancer that start there. The lymphatic system is a key part of the body's immune system. It is made up of lymph vessels, which carry a fluid called lymph throughout the body. Lymph contains white blood cells called lymphocytes, which are special cells that fight infections. The lymphatic system also includes lymph nodes scattered throughout the body. Other parts of the body that make up the lymphatic system are the tonsils, spleen, bone marrow, and thymus. Lymph tissue can also be found in many other organs, including parts of the digestive tract. The lymphatic system works to filter out bacteria, viruses, and other harmful substances from the body.

NHL most often starts in lymph nodes in the chest, neck, belly (abdomen), tonsils, and skin. But it also can start in the spleen or other lymph organs, or in lymph tissue found in other organs. Lymphocytes move throughout the body through the lymphatic system and bloodstream. Any abnormal lymphocytes can travel on thus pathway. Some NHLs stay in one spot in the body, but most have spread by the time lymphoma is diagnosed.

Lymph nodes increase in size when they fight an infection. These nodes are often tender to touch. An enlarged lymph node is usually not serious, especially if you have an infection such as a sore throat or a cold. But an enlarged lymph node is the most common sign of lymphoma.

You can't "catch" lymphoma like a cold. It's doesn't spread from person to person. NHL risk goes up as you get older, but exact causes of NHL are not known. Still, researchers have found some possible risk factors besides advancing age. They include working with or being exposed to chemicals such as pesticides, fertilizers, or solvents; being exposed to high doses of radiation; having the Epstein-Barr virus, the human T-lymphotropic virus type 1, HIV, or certain other infections; having certain immune system problems; or having an organ transplant.

Other symptoms can include swollen lymph nodes, fever, and night sweats. Fever may occur only at night for several days, go away for a while, and then return. The most common sign of NHL is the swelling of one or more lymph nodes. The swollen node usually doesn't hurt.

There are many types of NHL. Treatment depends on the type of the lymphoma and the extent of the disease. A slow-growing (low-grade) form may just be closely watched, with no treatment until it starts to grow or cause problems. Chemotherapy, radiation therapy, targeted therapy, and immunotherapy may be used for fast-growing forms of NHL, where starting treatment right away is more important. Stem cell transplants may be used if NHL comes back after treatment.