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 your body. It is also part of your 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 and begin to collect 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 confirm a diagnosis of non-Hodgkin lymphoma is by carrying out a biopsy (testing a sample of affected lymph node tissue).