Non-Hodgkin’s lymphoma, also called non-Hodgkin lymphoma, is a type of cancer that starts in the lymphocytes within the lymphatic system. Lymphocytes are a type of white blood cell which are found in the lymphatic system - a part of the body’s immune system which works to fight disease throughout the body. Non-Hodgkin's lymphoma is more common than the other general type of lymphoma, such as Hodgkin lymphoma. There are a number of different types of non-Hodgkin's lymphoma. The most common types of non-Hodgkin's lymphoma include diffuse large B-cell lymphoma and follicular lymphoma.

The symptoms of non-Hodgkin's lymphoma symptoms may include painless, swollen lymph nodes in your neck, armpits or groin, abdominal pain or swelling, chest pain, coughing or trouble breathing, fatigue, fever, night sweats, and weight loss.

It is unclear what causes non-Hodgkin's lymphoma. However, we do know that the disease occurs when the body produces too many abnormal lymphocytes. This does not normally happen with lymphocytes. Normally, old lymphocytes undergo apoptosis (aka die). After they die, the body simply produces new lymphocytes to replace the ones that have died. When a person has non-Hodgkin's lymphoma, the lymphocytes do not die. Instead, they keep growing, divide, and multiply. This causes an overproduction of lymphocytes in the body which causes in an excess of white blood cells in the lymph nodes. As a result, the lymph nodes swell.

Non-Hodgkin's lymphoma can begin in either the B cells or T cells. B cells fight infection by producing antibodies that get rid of foreign invaders. Most cases of non-Hodgkin's lymphoma are caused by B cells. T cells differ from B cells in that they kill foreign invaders directly. Non-Hodgkin's lymphoma cases are less often caused by T cells. Depending on whether non-Hodgkin's lymphoma starts in the B cells or T cells, treatment options may differ.  

Non-Hodgkin's lymphoma generally involves cancerous lymphocytes in the lymph nodes. However, the disease can also spread to other parts of the lymphatic system, such as the lymphatic vessels, tonsils, adenoids, spleen, thymus and bone marrow. Non-Hodgkin's lymphoma may also involve other organs outside of the lymphatic system.

Most people who have been diagnosed with non-Hodgkin's lymphoma do not have any risk factors. At the same time, many people who have risk factors for the disease never end up getting it. Risk factors that may increase the risk of developing non-Hodgkin's lymphoma include medications that suppress your immune system, infection with certain viruses and bacteria such as HIV, Epstein-Barr virus, or Helicobacter pylori, certain chemicals such as those used to kill insects, or older age. People can develop non-Hodgkin's lymphoma at any age. However, the risk increases with age. Most people who get non-Hodgkin’s lymphoma are aged 60 or older.