What is non-Hodgkin lymphoma in children?
Lymphoma is a type of cancer that starts in cells called lymphocytes, which are part of the body’s immune system. There are 2 kinds of lymphomas:
- Hodgkin disease (also known as Hodgkin lymphoma), which is named after Dr. Thomas Hodgkin, who first described it
- Non-Hodgkin lymphoma
These 2 types of lymphomas behave, spread, and respond to treatment differently.
Non-Hodgkin lymphoma and Hodgkin disease occur about equally in children and teens. Non-Hodgkin lymphoma usually occurs in younger children, while Hodgkin disease is more likely to affect older children and teens.
Hodgkin disease in children is very similar to Hodgkin disease in adults and is treated the same way. For more information on this disease, see our document called Hodgkin Disease.
The rest of this document focuses only on non-Hodgkin lymphoma in children.
The lymph system and lymphoid tissue
To understand non-Hodgkin lymphoma, it helps to know about the body's lymph system.
The lymph system (also known as the lymphatic system) is made up mainly of lymphoid tissue, lymph vessels, and a clear fluid called lymph. Lymphoid tissue includes the lymph nodes and related organs, such as the spleen and bone marrow, that are part of the body's immune and blood-forming systems.
Lymphoid tissue is made up of several types of immune system cells that help the body fight infections. Most of the cells in lymphoid tissue are lymphocytes, a type of white blood cell. The 2 main types of lymphocytes are B lymphocytes (B cells) and T lymphocytes (T cells). Normal B cells and T cells do different jobs within the immune system.
B lymphocytes: B cells normally help protect the body against germs (bacteria or viruses) by making proteins called antibodies. The antibodies attach to the germs, marking them for destruction by other parts of the immune system.
T lymphocytes: There are several types of T cells, each with a specialized job. Some T cells directly destroy cells infected with viruses, fungi, or certain kinds of bacteria. Other types of T cells play a role in either boosting or slowing the activity of other immune system cells.
Both types of lymphocytes can develop into lymphoma cells, but B-cell lymphomas are much more common in the United States than T-cell lymphomas. Different types of lymphoma can develop from each type of lymphocyte, based on how mature the cells are when they become cancerous and other factors.
Treatment for each lymphoma depends on which type it is, so determining the exact type of lymphoma is important.
Organs that have lymphoid tissue
Because lymphoid tissue is in many parts of the body, lymphomas can start almost anywhere. The major sites of lymphoid tissue are:
Lymph nodes: Lymph nodes are bean-sized collections of immune cells throughout the body. They can sometimes be felt under the skin in the neck, under the arms, and in the groin. Lymph nodes are made up mainly of lymphocytes.
Lymph nodes are connected to each other by a system of lymphatic vessels. These vessels are like veins, except that instead of carrying blood, they carry lymph and immune system cells traveling between lymph nodes and other tissues.
Lymph nodes get bigger when they fight infection. Lymph nodes that grow in reaction to infection are called reactive nodes or hyperplastic nodes and are often painful to the touch. An enlarged lymph node in a child is not usually a sign of a serious problem. Enlarged lymph nodes in the neck are often felt in children with sore throats or colds. But a large lymph node is also the most common sign of lymphoma. Lymph node enlargement is discussed more in the section, “How is non-Hodgkin lymphoma diagnosed in children?”
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.
Thymus: The thymus is a small organ behind the upper part of the breast bone and in front of the heart. Before birth, the thymus plays a vital role in development of T lymphocytes. The thymus shrinks and becomes less important over the first 20 years of life. Despite this, it continues to play a role in immune system function.
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. They are easy to see when they become enlarged during an infection, which occurs often in children, or if a lymphoma develops.
Digestive tract: The stomach and intestines, as well as many other organs, also contain lymphoid tissue.
Bone marrow: The bone marrow (the soft inner part of certain bones) makes red blood cells, blood platelets, and white blood cells. Red blood cells carry oxygen from the lungs to the rest of the body. Platelets help control bleeding by plugging up small holes in blood vessels. White blood cells fight infections. The 2 main types of white blood cells are granulocytes and lymphocytes. Bone marrow lymphocytes are primarily B cells. Lymphomas sometimes start from bone marrow lymphocytes.
Types of non-Hodgkin lymphoma in children
Lymphomas are most often classified by how the cancer cells look under the microscope. Key features include the size and shape of the cells and how they are arranged (their pattern of growth).
- Size is described as large or small.
- Shape is described as cleaved (showing folds or indentations) or non-cleaved.
- The growth pattern may be either diffuse (cancer cells are scattered) or follicular (cells are arranged in clusters).
Not every lymphoma is described using all 3 features (size, shape, and growth pattern). Special lab tests are often needed to accurately classify lymphomas. These are discussed in the section, “How is non-Hodgkin lymphoma diagnosed in children?”
Nearly all non-Hodgkin lymphomas in children belong to 1 of 3 main types:
- Lymphoblastic lymphoma
- Burkitt lymphoma (small non-cleaved cell lymphoma)
- Large cell lymphoma
All 3 types are high grade (meaning they grow quickly) and diffuse, but it is important to distinguish among them because they are treated differently.
There are many other types of non-Hodgkin lymphoma. These are much more common in adults and are rare in children, so they are not discussed further in this document.
Lymphoblastic lymphoma accounts for about 25% to 30% of lymphomas in children. It is most common in teens, and boys are affected about twice as often as girls.
The cancer cells of this lymphoma are very young lymphocytes called lymphoblasts. They are the same cells as those seen in acute lymphoblastic leukemia (ALL) in children. In fact, if more than 25% of the bone marrow is made up of lymphoblasts, the disease is classified and treated as ALL instead of lymphoma.
Most cases of lymphoblastic lymphoma develop from T cells and are called precursor T-lymphoblastic lymphomas. These lymphomas often start in the thymus, forming a mass in the area behind the breast bone, which can cause problems breathing. Trouble breathing may be the first symptom of lymphoblastic lymphoma.
Less often, this cancer may develop in the tonsils, lymph nodes of the neck, or other lymph nodes. It can spread very quickly to the bone marrow, other lymph nodes, the surface of the brain, and/or the membranes that surround the lungs and heart.
A small fraction of lymphoblastic lymphomas develop from B cells (precursor B-lymphoblastic lymphomas). These lymphomas more often begin in lymph nodes outside the chest, particularly in the neck. They can also involve the skin and bones.
Lymphoblastic lymphoma can grow very rapidly and can often interfere with breathing, so it needs to be diagnosed and treated quickly.
Burkitt lymphoma, also known as small non-cleaved cell lymphoma, accounts for about 40% of childhood non-Hodgkin lymphoma in the United States. It is most often seen in boys, usually around the age of 5 to 10 years old.
A subtype of Burkitt lymphoma, sometimes called Burkitt-like lymphoma or non-Burkitt lymphoma, shares some features with diffuse large B-cell lymphoma (described below) when seen under the microscope. But children with this subtype are treated the same way.
Burkitt lymphoma is named after the doctor who first described it in African children. In certain parts of Africa, Burkitt lymphoma accounts for nearly all childhood non-Hodgkin lymphoma and over half of all childhood cancers. For reasons that are not understood, in African children this lymphoma usually develops in the jaw or other facial bones.
Burkitt lymphomas in other areas of the world, including the United States, almost always start in the abdomen. Typically, a child will develop a large tumor in his or her abdomen that can sometimes block the bowels (intestines). This can cause belly pain, nausea, and vomiting. This lymphoma can also sometimes start in the neck or tonsils, or rarely in other parts of the body.
This lymphoma develops from B lymphocytes, and it is one of the fastest growing cancers known. It may spread to other organs, including the surface of the brain or inside the brain. Because of this, it must be diagnosed and treated quickly.
Large cell lymphomas
These lymphomas start in more mature forms of T cells or B cells and can grow almost anywhere in the body. They are not as likely to spread to the bone marrow or brain, nor do they grow as quickly as other childhood lymphomas. These lymphomas tend to occur more often in older children and teens. There are 2 main subtypes of large cell lymphoma.
Anaplastic large cell lymphoma: This lymphoma represents about 10% of all non-Hodgkin lymphoma in children. It usually develops from mature T cells. It may start in lymph nodes in the neck or other areas, and may be found in the skin, lungs, bone, digestive tract, or other organs.
Diffuse large B-cell lymphoma: This lymphoma accounts for about 15% of childhood lymphomas. It starts in B cells, as the name implies. These lymphomas often grow as large masses in the mediastinum (the space between the lungs), in which case they are referred to as primary mediastinal B-cell lymphomas. But they are also sometimes found in other areas such as lymphoid tissue in the neck or abdomen, or in the bones.
Treatment is the same for the different types of large cell lymphomas, although the cure rate tends to be slightly lower for the anaplastic type.
Last Medical Review: 10/09/2012
Last Revised: 01/17/2013