What are Lymph Nodes?
Lymph nodes (erroneously called lymph glands) are a part of the lymphatic system, a component of the body's immune system. Swollen lymph nodes may signal an infection.
There are several groups of lymph nodes, which are small, bean-shaped, soft nodules of tissue. The ones most frequently enlarged or swollen are found in the neck (a chain of lymph nodes is located in the front of the neck, the sides of the neck, and the back of the neck behind the ears), under the chin, in the armpits, and in the groin. There is also a large group of lymph nodes in the chest and abdomen, which are sometimes found to be enlarged on X-rays or CT scans.
- The lymphatic system consists of nodes and ducts spread throughout the body. They bring the lymph [the tissue fluid surrounding the cells, which contains white blood cells (lymphocytes), fluid from the intestines (chyle), and some red blood cells] back into the circulation through the veins. Lymph contains a concentration of infectious and other foreign substances (antigens).
- Lymph nodes are small clusters of cells, surrounded by a capsule. Ducts go into and out of them. The cells in lymph nodes are lymphocytes, which produce antibodies (protein particles that bind foreign substances including infectious particles) and macrophages which digest the debris. They act as the "cleaner" cells of the body.
- The lymph nodes are a major site where foreign substances and infectious agents interact with the cells of the immune system. A major cluster of the lymph nodes is the spleen, which, apart from other functions, also helps fight infections and responds to foreign substances in the body.
What Causes Swollen Lymph Nodes?
Several mechanisms can cause the lymph nodes to enlarge (swell).
- Infection (lymphadenitis): This can increase the number of white blood cells, which multiply in response to stimulation with a foreign substance (antigen). Swollen lymph nodes under the arm (in the armpit) can occur due to infection or injury to the arm or hand. Some infections (mononucleosis or "mono," HIV, and fungal or parasitic infections) may cause generalized swelling of lymph nodes throughout the body.
- Virus: Immune reaction to a generalized infection in the body such as viral infections that can occur with the common cold as well as more serious infections such as HIV.
- Inflammation: Infiltration with inflammatory cells during infection or inflammation in a region of a given lymph node. Some immune disorders, such as lupus or rheumatoid arthritis, may also cause generalized lymph node swelling.
- Cancer: Infiltration with malignant cells (metastases) brought to the node with the lymph flowing from an area of certain types of cancer. In rare cases, breast cancer or lymphoma may cause swollen lymph nodes in the armpit. Rarely, a person may have a node or group of nodes that grows rapidly and becomes hard and can not be easily moved around under the skin. These may indicate a tumor.
- Cancer of the blood: Uncontrolled, malignant multiplication of lymphocytes as in lymphoma or leukemia.
How to Test Swollen Lymph Nodes
- The doctor will ask the person about any associated symptoms and perform a physical examination.
- Depending on the extent of the problem, the doctor may order blood tests, X-rays, and a CT scan of the affected area.
- On follow-up, a biopsy of the swollen node may be needed. A sample of the tissue may be taken out by withdrawing cells from the lymph node with a thin needle (fine needle aspiration or biopsy). In other cases a lymph node itself or a portion of a lymph node may be removed for examination. In all these cases the tissue is examined by a pathologist under a microscope to determine the cause of the swelling.
