Hodgkin disease (Hodgkin lymphoma) is a type of lymphoma, a cancer that starts in white blood cells called lymphocytes. Lymphocytes are part of the immune system.
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?
Types of lymphoma
There are 2 kinds of lymphomas:
- Hodgkin disease (named after Dr. Thomas Hodgkin, who first recognized it)
- Non-Hodgkin lymphoma
These types of lymphomas differ in how they behave, spread, and respond to treatment, so it is important to tell them apart. Doctors can usually tell the difference between them by looking at the cancer cells under a microscope or by using sensitive lab tests.
Both children and adults can develop Hodgkin disease. This document discusses treatment in both groups.
For information on non-Hodgkin lymphoma, see Non-Hodgkin Lymphoma.
The lymph system and lymphoid tissue
To understand what Hodgkin disease is, it helps to know how the lymph system works.
The lymph system (also known as the lymphatic system) is part of the immune system, which helps fight infections and some other diseases. It also helps fluids move in the body. The lymph system is composed mainly of:
- Lymphoid tissue: includes the lymph nodes and related organs (see below) that are part of the immune and blood-forming systems
- Lymph: a clear fluid that travels through the lymph system, carrying waste products and excess fluid from tissues, as well as lymphocytes and other immune system cells
- Lymphatic vessels: small tubes, similar to blood vessels, through which lymph travels to different parts of the lymph system
Lymphoid tissue is made up mainly of cells called lymphocytes, a type of white blood cell. The 2 major types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells). Normal B cells and T cells have different jobs.
- B lymphocytes: B cells help protect the body from germs (bacteria and viruses) by making proteins called antibodies. The antibodies attach to the germs, marking them for destruction by other parts of the immune system. Almost all cases of Hodgkin disease start in B lymphocytes.
- T lymphocytes: There are several types of T cells, and each has a special job. Some T cells directly destroy certain kinds of bacteria or cells infected with viruses or fungi. Other types of T cells play a role in either boosting or slowing the activity of other immune system cells.
Organs that have lymphoid tissue
Because lymphoid tissue is in many parts of the body, Hodgkin disease can start almost anywhere.
The major sites of lymphoid tissue are:
Lymph nodes: Lymph nodes are bean-sized collections of lymphocytes and other immune system cells throughout the body, including inside the chest, abdomen, and pelvis. They can sometimes be felt as small lumps under the skin in the neck, under the arms, and in the groin. Lymph nodes are connected to each other by a system of lymphatic vessels.
Lymph nodes get bigger when they fight an infection. Lymph nodes that grow because of infection are called reactive or hyperplastic nodes. These often hurt when they are touched. People with sore throats or colds might have enlarged neck lymph nodes. An enlarged lymph node is not always a sign of a serious problem, but it can be a sign of Hodgkin disease. See “Signs and symptoms of Hodgkin disease” for more information.
Spleen: The spleen is an organ under the lower part of the rib cage on the left side of the body. The spleen makes lymphocytes and other immune system cells to help fight infection. It also stores healthy blood cells and filters out damaged blood cells, bacteria, and cell waste.
Bone marrow: The bone marrow is the spongy tissue inside certain bones, which is where new white blood cells (including some lymphocytes), red blood cells, and platelets are made.
Thymus: The thymus is a small organ behind the upper part of the breastbone and in front of the heart. It is important in the development of T lymphocytes.
Adenoids and tonsils: These are collections of lymphoid tissue in the back of the throat. They help make antibodies against germs that are breathed in or swallowed.
Digestive tract: The stomach, intestines, and many other organs also have lymphoid tissue.
Start and spread of Hodgkin disease
Because lymphoid tissue is in many parts of the body, Hodgkin disease can start almost anywhere. Most often it starts in lymph nodes in the upper part of the body. The most common sites are in the chest, in the neck, or under the arms.
Hodgkin disease most often spreads through the lymph vessels in a stepwise fashion from lymph node to lymph node. Rarely, and late in the disease, it can invade the bloodstream and spread to other parts of the body, including the liver, lungs, and/or bone marrow.
Types of Hodgkin disease
Different types of Hodgkin disease are classified by how they look under the microscope. This is important because types of Hodgkin disease may grow and spread differently and may be treated differently. The 2 main types are:
- Classic Hodgkin disease (which has several subtypes)
- Nodular lymphocyte predominant Hodgkin disease
All types of Hodgkin disease are malignant (cancerous) because as they grow they can invade and destroy normal tissue and spread to other tissues.
Classic Hodgkin disease
Classic Hodgkin disease (HD) accounts for about 95% of all cases of Hodgkin disease in developed countries.
The cancer cells in classic HD are called Reed-Sternberg cells (after the 2 doctors who first described them). These cells are usually an abnormal type of B lymphocyte. Reed-Sternberg cells are much larger than normal lymphocytes and also look different from the cells of non-Hodgkin lymphomas and other cancers.
The enlarged lymph nodes in classic HD usually have a small number of Reed-Sternberg cells and a large number of surrounding normal immune cells. It is mainly these other immune cells that account for the enlarged lymph nodes.
Classic HD has 4 subtypes:
Nodular sclerosis Hodgkin disease: This is the most common type of Hodgkin disease in developed countries, accounting for about 60% to 80% of cases. It is most common in teens and young adults, but it can occur in people of any age. It tends to start in lymph nodes in the neck or chest.
Mixed cellularity Hodgkin disease: This is the second most common type (15% to 30%) and is seen mostly in older adults (although it can occur at any age). It can start in any lymph node but most often occurs in the upper half of the body.
Lymphocyte-rich Hodgkin disease: This subtype accounts for about 5% of Hodgkin disease cases. It usually occurs in the upper half of the body and is rarely found in more than a few lymph nodes.
Lymphocyte-depleted Hodgkin disease: This is the least common form of Hodgkin disease, making up less than 1% of cases. It is seen mainly in older people. The disease is more likely to be advanced when first found, in lymph nodes in the abdomen as well as in the spleen, liver, and bone marrow.
Nodular lymphocyte predominant Hodgkin disease
Nodular lymphocyte predominant Hodgkin disease (NLPHD) accounts for about 5% of Hodgkin disease. The cancer cells in NLPHD are large cells called popcorn cells (because they look like popcorn), which are variants of Reed-Sternberg cells.
NLPHD usually starts in lymph nodes in the neck and under the arm. It can occur in people of any age, and is more common in men than in women.
Last Revised: 02/09/2016