Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Non-Hodgkin Lymphoma

What Is It?

Non-Hodgkin lymphoma is a group of about 30 different blood cancers. It is also called non-Hodgkin's lymphoma, NHL, or lymphoma.

Non-Hodgkin lymphoma begins in the lymph system. The lymph (or lymphatic) system is part of the immune system. It collects and destroys invading organisms such as viruses and abnormal cells. The lymph system protects the body from infection and disease.

The lymph system is a network of tissue, vessels, and fluid (lymph). Lymph nodes are part of the lymphatic system. They filter lymph and store white blood cells (lymphocytes).

Lymph nodes are located in the neck, underarms, chest, abdomen, pelvis, and groin. Lymph tissue also resides in the spleen, thymus gland, tonsils, bone marrow, and digestive system.

Lymphatic tissue is composed mainly of lymphocytes. There are two main types of lymphocytes:

• B cells make proteins called antibodies that kill bacteria or viruses.

• T cells play several different roles in the immune system.

Most cases of non-Hodgkin lymphoma develop from B lymphocytes.

Non-Hodgkin lymphoma starts when a lymphocyte changes into an abnormal cell that begins dividing out of control. These abnormal cells often form masses (tumors) in lymphatic tissue such as lymph nodes.

Because lymph tissue is located throughout the body, NHL can begin almost anywhere and spread to other tissues and organs.

NHL is different from Hodgkin's disease. Patients with Hodgkin's disease are generally younger than those with NHL. They also have a specific type of abnormal cell in their cancerous lymph nodes and different symptoms. Treatments also vary.