Lymph nodes (also called lymph glands) are small oval structures scattered all over the body. Lymph nodes contain white blood cells (WBCs), and especially the WBCs known as lymphocytes. Different types of lymphocytes grow and mature inside a lymph node, and these immune cells help the body fight infections. Lymph nodes are a part of the lymph system of the body.

Lymph nodes are connected to each other by lymph channels called the lymphatics—small tubes (like blood vessels)—through which lymph fluid, as well as proteins and other substances, moves from one part of the body to another.

Lymph nodes in different parts of the body are named differently

Cervical lymph nodes—lymph nodes in the neck
Axillary lymph nodes—lymph nodes in the armpits
Mediastinal lymph nodes—nodes inside the chest, near the heart
Inguinal lymph nodes—those in the groin
Retroperitoneal and mesenteric lymph nodes—lymph nodes in different parts of the abdomen
Pelvic lymph nodes—lymph nodes in the pelvis

When lymph nodes increase in size, they are called enlarged lymph nodes. When enlarged nodes can be felt by the doctor (in areas like the neck, armpits, and groin) they are called palpable lymph nodes.

More on Enlarged Nodes

Lymph nodes can increase in size in a number of conditions. Infections, cancer, and many immune diseases can affect lymph cells and cause an enlargement of lymph nodes. Enlarged lymph nodes are often the first sign of lymphoma, a cancer of lymph cells. But all enlarged nodes are not lymphoma.

Enlarged lymph nodes should not be ignored. However, since there are many non-cancerous causes of lymph node enlargement, doctors rarely go straight to a lymph node biopsy right away, when an enlarged node is detected. You should feel free to bring to your doctor's attention any odd lumps or bumps—and many common bumps turn out not to be lymph nodes at all.

If you do have palpable lymph nodes, your doctor is trained to track down the most likely reasons first. Upper respiratory infections, for instance, are among the most common causes of swollen lymph nodes, such as those that might be palpated in the neck. Even when the reason for an enlarged lymph node is not immediately obvious to the doctor, it is not uncommon to wait and see if the swelling goes away on its own, after a brief period, before investigating further. However, a persistently enlarged node needs to be evaluated.

What Kinds of Things Cause Swollen Lymph Nodes?

Here is an old memory device that some doctors may still recall. Hodgkin's disease is just one possibility, but it serves as the skeleton for this mnemonic. It doesn't cover everything, but it is useful for thinking about diseases associated with lymphadenopathy, or swollen lymph nodes. Generalized lymphadenopathy means there are more than two nodes involved from different areas. As you can see, there are many possible causes:

H. Hematologic: Hodgkin’s disease, leukemia, and non-Hodgkin’s lymphoma

O. Oncologic: Metastasis to lymph node, malignant melanoma

D. Dermatopathic lymphadenitis: swollen lymph nodes that drain a patch of skin that has been disrupted or irritated

G. Gaucher’s disease: a rare genetic disease

K. Kawasaki’s disease: a rare autoimmune disease involving the blood vessels and inflammation

I. Infections: bacterial, viral, and parasitic

N. Niemann–pick disease: a genetic disease that involves metabolism

S. Serum sickness: an immune response to certain medications or treatments

D. Drug reaction: response to certain drugs

I. Immunological disease: for example, rheumatoid arthritis and lupus

S. Sarcoidosis: an inflammatory disease that can affect different parts of the body

E. Endocrine: hyperthyroidism