Non-Hodgkin lymphoma

Non-Hodgkin lymphoma (which is also known as "B-cell" and "T-cell lymphomas") is a cancer of the lymphatic system. The lymphatic system is a network of vessels and glands spread throughout the body. It is also part of the immune system. Clear fluid called "lymph" flows through the lymphatic vessels and contains infection-fighting white blood cells known as "lymphocytes".
In lymphoma, these lymphocytes start to multiply in an abnormal way. A lot of them appear in certain parts of the lymphatic system, such as the lymph nodes (glands). The affected lymphocytes lose their infection-fighting properties making you more vulnerable to infection.
The most common symptom of non-Hodgkin lymphoma is a painless swelling in a lymph node, usually in the neck, armpit or groin.
The usual way to know that a person has non-Hodgkin lymphoma is to do a biopsy (testing a sample of affected lymph node tissue).