What is non-Hodgkin lymphoma?

Non-Hodgkin lymphoma (NHL) is a cancer that starts in lymphocytes. Lymphocytes are cells of the lymphatic system.

The lymphatic system

The lymphatic system works with other parts of your immune system to help your body fight infection and disease. The lymphatic system is made up of a network of lymph vessels, lymph nodes and the lymphatic organs. Lymph vessels carry lymph fluid, which contains lymphocytes and other white blood cells, antibodies and nutrients. Lymph nodes sit along the lymph vessels and filter lymph fluid. The lymphatic organs include the spleen, thymus, adenoids, tonsils and bone marrow.

Lymphocytes develop in the bone marrow from basic cells called stem cells. Stem cells develop into different types of cells that have different jobs. Lymphocytes are types of white blood cells that help fight infection. The main types of lymphocytes are:

  • B cells make antibodies to fight bacteria, viruses and other foreign material such as fungi.
  • T cells fight infection, destroy abnormal cells and control the immune response.
  • Natural killer (NK) cells attack abnormal or foreign cells.

Lymphocytes sometimes change so they no longer grow or behave normally. These abnormal cells can form tumours called lymphomas.

Because lymphocytes are found throughout the lymphatic system, NHL can start almost anywhere in the body. It usually starts in a group of lymph nodes in one part of the body, such as in the neck, above the collarbone, under the arms, in the abdomen or in the groin.

NHL can spread to almost any tissue or organ in the body through the lymphatic system or the bloodstream. Abnormal lymphocytes, or lymphoma cells, may stay in the lymph nodes or form solid tumours in the body. In rare cases, they circulate in the blood.

Diagram of the lymphatic system
Diagram of the lymphatic system

Types of NHL

There are more than 30 different types of NHL. They are grouped based on the type of lymphocyte they started from. Most types of NHL start in B cells and are called B-cell lymphoma. NHL can also start in T cells, which is called T-cell lymphoma. NHL that starts in NK cells is grouped with T-cell lymphomas.

The different types of NHL look different under a microscope. They also develop and grow differently. The grade of NHL is based on how different, or abnormal, the lymphoma cells look compared to normal lymphocytes. The grade gives doctors an idea of how slowly or quickly the NHL will likely grow and spread. NHL is usually divided into 2 grades:

  • Indolent (low-grade) NHL means that the cancer cells are well differentiated. They look and act much like normal cells. These NHLs tend to grow slowly.
  • Aggressive (high-grade) NHL means that the cancer cells are poorly differentiated or undifferentiated. They look and act less normal, or more abnormal. These NHLs tend to grow quickly.

World Health Organization (WHO) classification system

Doctors use the WHO classification system to identify the type of NHL. Each type can behave differently and may need different treatments.

The WHO classifies NHL based on the type of lymphocyte (B cell or T cell) that has become cancerous. NHL that starts in natural killer (NK) cells is grouped with T-cell lymphomas.

The WHO divides B-cell and T-cell lymphomas into 2 groups based on the stage of development, or maturation, of the lymphocytes when they became cancerous. Precursor lymphomas develop in immature lymphocytes during the earliest stages of their development. Mature lymphomas (also called peripheral lymphomas) develop in more mature lymphocytes.

The specific type of NHL is based on how the abnormal lymphocytes, or lymphoma cells, look under the microscope, characteristics of chromosomes in the lymphoma cells and if there are certain proteins on the surface of the lymphoma cells.

The WHO includes both lymphomas and lymphocytic leukemias as types of NHL. They both start in lymphocytes, but the lymphoma cells are found in different places in the body. If tumours develop in the lymph nodes or other organs, it is considered a lymphoma. If the lymphoma cells are in the blood or bone marrow and a tumour develops, it is considered a leukemia lymphoma.

Other cancers of the lymphatic system are called Hodgkin lymphoma (HL). The abnormal cells of Hodgkin lymphoma look and behave differently from non-Hodgkin lymphoma cells. Hodgkin lymphomas and non-Hodgkin lymphomas are treated differently.

Expert review and references

The lymphatic system

The lymphatic system drains extra fluid (called lymph) that has passed out of the blood and into tissues and returns it back to the blood. The lymphatic system is a circulatory system made up of lymph vessels much like blood vessels. The lymphatic system also includes tissues and organs that make, store and release lymphocytes (a type of white blood cell).

Diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of NHL. Some other types of NHL can change into DLBCL. Learn about DLBCL.

Follicular lymphoma

Follicular lymphoma is the 2nd most common type of NHL. There may not be any symptoms other than enlarged lymph nodes. Learn about follicular lymphoma.

MALT lymphoma

MALT lymphomas are a type of B-cell NHL. Most MALT lymphomas start in the stomach. Learn about MALT lymphoma.

Mantle cell lymphoma

Mantle cell lymphoma occurs more often in men than in women. It is usually diagnosed in people in their early 60s. Learn about mantle cell lymphoma.

More types of non-Hodgkin lymphoma

Lymphoma is a cancer that affects a type of white blood cell called a lymphocyte. Lymphocytes are immune cells that normally protect us from illness. Find out more about types of non-Hodgkin lymphoma.

Adult T-cell leukemia lymphoma

Learn about adult T-cell leukemia/lymphoma. It occurs most often in places where the HTLV-1 virus is more common such as the Caribbean and parts of Africa.

Aggressive NK-cell leukemia

Aggressive NK-cell leukemia (ANKL) is a rare type of NHL. It usually develops in people from Asia, Central America and South America. Learn about ANKL.

AIDS-related lymphoma

Non-Hodgkin lymphoma is the most common type of lymphoma that affects people with AIDS. Learn about the main types of AIDS-related lymphomas.

Anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is a rare type of T-cell lymphoma. ALCL can occur at any age, but it is more common in children and young adults. It affects more men than women.

Angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (ATCL, or AITL) is more common in the elderly and has been linked to the Epstein-Barr virus. Learn about ATCL.

Burkitt lymphoma

Burkitt lymphoma occurs most often in children and young adults. Most people are infected with the Epstein-Barr virus. Learn about Burkitt lymphoma.

Chronic lymphocytic leukemia and small lymphocytic lymphoma

Chronic lymphocytic leukemia and small lymphocytic lymphoma are often considered different versions of the same disease. Learn about this type of NHL.

Cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is a group of lymphomas that affect the skin. Learn about the symptoms of the different types and treatments for CTCL.

Enteropathy-associated T-cell lymphoma

Enteropathy-associated T-cell lymphoma (EATL) is a very rare type of non-Hodgkin lymphoma (NHL). The most common type of EATL is linked to celiac disease or gluten sensitivity. Learn about EATL.

Extranodal NK/T-cell lymphoma, nasal type

Extranodal NK/T-cell lymphoma, nasal type, is a fast-growing, type of NHL. It is linked to the Epstein-Barr virus. Learn about this type of NHL.

Hepatosplenic T-cell lymphoma

Hepatosplenic T-cell lymphoma (HSTL, or HSTCL) is very rare. Sometimes it develops in people whose immune system isn’t working properly. Learn about HSTL.

Intravascular large B-cell lymphoma

Intravascular large B-cell lymphoma (ILCL) is a fast growing type of NHL. It is usually treated with chemotherapy and targeted therapy. Learn about ILCL.

Lymphoblastic lymphomas

Lymphoblastic lymphomas are most common in adolescents and young adults. They develop most often in young men. Learn about lymphoblastic lymphomas.

Lymphoplasmacytic lymphoma

Lymphoplasmacytic lymphoma cells have characteristics of both lymphocytes and plasma cells. Learn about lymphoplasmacytic lymphoma.

Nodal marginal zone lymphoma

Nodal marginal zone lymphoma usually affects only the lymph nodes but may develop in other organs. Learn about nodal marginal zone lymphoma.

Peripheral T-cell lymphoma, unspecified

Peripheral T-cell lymphoma, unspecified (PTCLU) usually occurs in people in their 60s more often in men than in women. Learn about PTCLU.

Post-transplant lymphoproliferative disorder

Post-transplant lymphoproliferative disorder (PTLD) is a complication that can develop after an organ transplant. Learn about PTLD.

Primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) starts in the brain, spinal cord, meninges or eyes. Learn about primary central nervous system lymphoma.

Primary effusion lymphoma

Primary effusion lymphoma (PEL) is rare subtype of diffuse large B-cell lymphoma (DLBCL). It is also considered a distinct type of non-Hodgkin lymphoma (NHL) in the World Health Organization (WHO) classification system. PEL may also be called body cavity lymphoma.

Primary mediastinal large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) occurs in the thymus or in lymph nodes in the centre of the chest. Learn about PMBCL.

Prolymphocytic leukemias

Prolymphocytic leukemias (PLLs) are rare lymphocytic leukemias but are also like lymphomas because they start in the lymphocytes. Learn about PLLs.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is slow-growing, type of NHL. It is linked with viral infections, including hepatitis C virus. Learn about SMZL.

Subcutaneous panniculitis-like T-cell lymphoma

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) causes lumps to form under the skin on the legs, chest, belly or back. Learn about SPTCL.

T-cell large granular lymphocytic leukemia

T-cell large granular lymphocytic (TLGL) leukemia is seen in people with rheumatoid arthritis or another autoimmune disease. Learn about TLGL leukemia.