Non-Hodgkin lymphoma (NHL)
Non-Hodgkin lymphoma (NHL) is a type of blood cancer that affects specialized white blood cells called lymphocytes. Lymphocytes work together with other cells in the immune system to defend the body against invasion by bacteria, viruses, parasites, and other foreign substances. Lymphocytes travel in the bloodstream and in another network of mostly small vessels called the lymphatic system.
Lymphocytes are also found in specialized structures called lymph nodes, in the bone marrow, and in the spleen. Lymph nodes are part of the lymphatic system and typically are the sites in which the body develops an immune response to viruses and bacterial infections.
What Is Cancer?
The body is made up of many different types of specialized cells that are organized into tissues and organs that perform the tasks needed to sustain life. To keep the body running smoothly, cells in the body grow, work, and multiply in a very controlled fashion.
All normal cells have a limited lifespan. A self-destruct mechanism is triggered when cells become senescent (too old) or get damaged; this process is called apoptosis or programmed cell death. However, sometimes damage to the genetic material (DNA) of a cell gives it the ability to override this self-destruct mechanism and allows the cell to continue to live and grow indefinitely, making the cell “immortal” in many ways. Unless the body’s immune system gets rid of these abnormal cells, they can become cancerous.
Cancer, or malignancy, is a disease in which abnormal cells gain the ability to multiply uncontrollably. When these cells accumulate, they form a mass called a tumor that can interfere with normal organ function.
Most cancers are named after the organ or cell type of their origin. For almost every normal cell in the body, there is a corresponding cancer. For example:
■ A cancer that started in the pancreas is called pancreatic cancer.
■ A cancer of the lymphocytes is called a lymphoma or a lymphocytic leukemia depending on whether the cancerous lymphocytes reside primarily in the lymph nodes and other lymphatic tissues (lymphoma) or primarily in the bone marrow and the blood (lymphocytic leukemia).
What Is Non-Hodgkin Lymphoma?
In the United States, NHL (including chronic lymphocytic leukemia and small lymphocytic lymphoma) is the fifth most common type of cancer affecting adults. NHL is not a single disease but rather a large group of several closely related cancers that come from abnormal lymphocytes. The World Health Organization estimates that there are more than 80 types of NHL. While these various types share many common features, certain characteristics set them apart from each other, including:
■ How they look when examined under a microscope
■ Genetic and other molecular characteristics
■ How and where they grow in the body
■ How their growth and spread affect patients
■ How the disease should be treated
■ Likely outcome of treatment (curable vs. not curable [but treatable])
NHL is divided into the following two major groups:
■ B-cell lymphomas — These lymphomas develop from abnormal B lymphocytes and are the most common, comprising about 92 percent of all cases of NHL in the United States.
■ T/NK-cell lymphomas — These lymphomas develop from abnormal T lymphocytes or NK cells, are less common, and constitute about seven percent of patients with an NHL diagnosis.
Another way to group NHL types is by how quickly they grow:
■ Indolent (also called low-grade) lymphomas usually grow slowly and initially tend to exhibit few symptoms. Indolent lymphomas are generally not curable (similar in some ways to chronic diseases such as diabetes, which is not curable but usually manageable). However, patients can live a long time with these types of lymphomas because they tend to respond well to treatment and can remain in remission (disappearance of signs and symptoms) for many years, even decades. Over time, some indolent lymphomas may “transform” or develop into aggressive lymphomas.
■ Aggressive lymphomas grow and spread more quickly than indolent lymphomas. However, aggressive lymphomas can be cured by chemotherapy agents that kill rapidly dividing tumor cells.
Indolent B-Cell Lymphomas
Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma
Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are a type of lymphoma involving small lymphocytes that can be primarily in the bone marrow and blood (“leukemia”) or primarily in the lymph nodes (“lymphoma”). While these used to be considered two separate diseases, recent research has shown that CLL and SLL are essentially the same disease. If the malignant lymphocytes are found mainly in the lymph nodes, the disease is called SLL. If more than 5,000 malignant lymphocytes per microliter of blood are found in the bloodstream, then the disease is called CLL. Because they are essentially the same disease presenting in different parts of the body, the two terms are grouped together as ‘CLL/SLL.’
The most common signs and symptoms of CLL/SLL are swollen lymph nodes, fatigue, and shortness of breath, anemia, bruising easily, and frequent infections. However, about 25 to 50 percent of patients may not experience any signs or symptoms, so CLL/SLL is often discovered during routine blood tests and/or a physical examination. More than half of CLL/SLL cases occur in people over the age of 70. Over time, CLL may occasionally progress to a more aggressive type of lymphoma, typically diffuse large B-cell lymphoma (DLBCL); this is called a Richter transformation.
Follicular lymphoma (FL) is one of the most common types of NHL in the United States, with over 31,000 people newly diagnosed each year. Although it can affect people at any age, the average age at diagnosis is 60. FL usually appears in lymph nodes throughout the body, causing them to swell. Often one of the first signs is painless swelling in the neck, underarms, or groin caused by these enlarged lymph nodes. FL may eventually transform into a more aggressive form of the disease
Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia
Lymphoplasmacytic lymphoma is an uncommon B-cell lymphoma, with about 5,300 people newly diagnosed in the United States each year. About 55 percent of cases are characterized by abnormally high levels of a protein called immunoglobulin M (IgM) or paraprotein, which can cause thickening of the blood (hyperviscosity); these patients are said to have Waldenström macroglobulinemia.
The disease usually affects older adults and is primarily found in the bone marrow, although the lymph nodes and spleen may sometimes be involved. Symptoms include fatigue, increased bleeding or bruising easily, headache, dizziness, visual changes, abdominal pain, and swollen lymph nodes.
Marginal Zone Lymphoma
Marginal zone lymphoma (MZL) is a B-cell lymphoma that accounts for almost seven percent of all B-cell NHLs. The average age at diagnosis is 60. There are three types of MZL based on location in the body: (1) extranodal MZL (ENMZL; also called mucosa-associated lymphoid tissue [MALT]) occurs outside the lymphatic system; (2) nodal MZL occurs within the lymph nodes; and (3) splenic MZL (SMZL) occurs mostly in the spleen and blood.
Many people who develop ENMZL have a history of inflammation, infection, or autoimmune disorders. For example, chronic inflammation associated with Helicobacter pylori (H. pylori; a bacterial pathogen that can cause gastritis and stomach ulcers) may increase the risk of developing ENMZL of the stomach lining.
Different types of infections have also been implicated in other forms of MZL, including Campylobacter jejuni (intestinal tract) and Chlamydia psittaci (lacrimal – tear gland of the eye). For this reason, some MZLs can be successfully treated with anti-infective agents. However, the presence of any of these bacterial infections does not necessarily mean that someone has MZL.
Patients with SMZL may have an enlarged spleen. These lymphomas have been associated with hepatitis C virus (HCV) infection, and they may improve after treatment for the HCV infection.
Indolent T-Cell Lymphomas
Cutaneous T-Cell Lymphoma
Cutaneous T-cell lymphoma (CTCL) is a general term for a group of T-cell lymphomas that originate in the skin. The disease affects men more often than women and usually occurs in men in their 40s, 50s, and 60s. Most forms of CTCL are indolent and involve only skin symptoms, although some forms of CTCL can involve the blood, lymph nodes, and other organs.
Mycosis fungoides is the most common type of CTCL, accounting for approximately one-half of all CTCLs. This type of lymphoma is indolent and usually develops very slowly. Patients with mycosis fungoides may have various types of lesions, including:
■ Patches, which are usually flat, possibly scaly, and look like a rash
■ Plaques, which are thicker, raised, usually itchy lesions that are often mistaken for eczema, psoriasis, or dermatitis
■ Tumors, which are raised bumps that may ulcerate (become an open sore)
Common Types of Aggressive Non-Hodgkin B-Cell and T-Cell Lymphomas
Aggressive B-Cell Lymphomas
Burkitt lymphoma is a rare, highly aggressive B-cell NHL. There are three main types:
■ Endemic Burkitt lymphoma is the most common type and is primarily found in Africa, where it is the most common childhood cancer. This type is rare outside of Africa.
■ Sporadic Burkitt lymphoma occurs throughout the world. The sporadic form seen in the United States accounts for about one percent of all B-cell NHLs in adults, and about five percent of all childhood lymphomas.
■ Immunodeficiency-related Burkitt lymphoma can occur in patients who have human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS); in those who have inherited immune deficiencies; and in those who take immunosuppressive medications to prevent rejection after organ transplant.
The Epstein-Barr virus (EBV) has been shown to be linked to the development of Burkitt lymphoma. The greatest association between EBV and Burkitt lymphoma is seen with the endemic form.
Burkitt lymphoma may affect the jaw, central nervous system (CNS), bowel, kidneys, ovaries, or other organs. The sporadic and immunodeficiency-related types usually cause a mass to develop in the abdomen. Other symptoms include weight loss, loss of appetite, fatigue, fever, and night sweats. Burkitt lymphoma is potentially curable when treated aggressively.
Diffuse Large B-Cell Lymphoma
Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma in the United States, accounting for 23 percent of patients with newly diagnosed NHL. Although it can occur in childhood, the frequency of DLBCL generally increases with age, and most patients are over the age of 60 at diagnosis. The first sign of DLBCL is usually rapid swelling in the neck, underarms, or groin caused by enlarged lymph nodes. Other symptoms include night sweats, chills, unexplained fevers, and weight loss.
DLBCL can develop in the lymph nodes or outside the lymphatic system. It may be localized or spread throughout the body. The three primary subtypes are activated B-cell–like (ABC), germinal center B-cell–like (GCB), and primary mediastinal B-cell (PMBC) lymphoma. Despite being aggressive, DLBCL is curable in many patients. The treatment approach may depend on the DLBCL subtype. For example, the GCB subtype is more likely to respond to the standard chemotherapy regimen than the ABC subtype.
Double-hit lymphoma (DHL) is a type of aggressive B-cell NHL characterized by rearrangements (parts of genes switch places within chromosomes) in the c-MYC gene and the Bcl2 and/or Bcl6 gene. The appearance of DHL under the microscope often resembles DLBCL but can also have some features of Burkitt lymphoma. Although many cases of DHL arise spontaneously, indolent lymphomas can transform into DHL as well. DHL is usually a very fast-growing type of lymphoma that requires intensive treatment.
Mantle Cell Lymphoma
Mantle cell lymphoma (MCL) accounts for about three percent of all patients with B-cell NHLs. This type of lymphoma more frequently affects men, and the median age at diagnosis is 60. At the time of diagnosis, MCL is often present in several lymph nodes, in one or more organs (often the intestines), and in the bone marrow. MCL may follow an indolent course that does not require therapy initially. Most cases, however, behave more aggressively and require treatment as an aggressive lymphoma.
Primary Mediastinal B-Cell Lymphoma
Primary mediastinal B-cell lymphoma (PMBCL) is a form of DLBCL that arises in the thymus gland and is usually limited to the mediastinum (a compartment in the central part of the chest that includes the heart, thymus, esophagus, and trachea). Most patients are 30 to 40 years of age at diagnosis, and the disease is more common in women. Symptoms include fever, weight loss, night sweats, and superior vena cava syndrome, which is a swelling of the face and arms and shortness of breath caused by compression of the major vein that delivers blood to the heart. Patients with PMBCL usually have a better prognosis than those with other subtypes of DLBCL, and most patients can be cured.
Aggressive T-Cell Lymphomas
Lymphoblastic leukemia/lymphoma is relatively rare and can originate from both B cells and T cells, but about 85 percent of all cases involve T cells. Although 25 to 30 percent of T-cell lymphoblastic leukemia/lymphoma cases are diagnosed in children, the disease is also common in young adults, and it tends to occur in males more often than females. Lymphoblastic leukemia/lymphoma is aggressive and progresses rapidly, with more than 70 percent of patients presenting with advanced disease at diagnosis. Experts suggest that lymphoblastic leukemia/lymphoma and acute lymphoblastic leukemia (ALL) may be the same disease. Symptoms include swollen lymph nodes, fever, night sweats, unexplained weight loss, fatigue, and bruising easily. The complete remission (disappearance of signs and symptoms) rate after combination chemotherapy is usually very high.
Peripheral T-Cell Lymphoma
Peripheral T-cell lymphoma (PTCL) refers to a group of “mature” T-cell lymphomas that together account for approximately 54 percent of all patients diagnosed with T-cell NHL in the United States. The most common subtypes include PTCL not otherwise specified (PTCLNOS), cutaneous T-cell lymphoma (CTCL), angioimmunoblastic T-cell lymphoma (AITL), and anaplastic large cell lymphoma (ALCL). PTCLs typically develop in tissues outside of the bone marrow such as the lymph nodes, spleen, gastrointestinal tract, and skin. Most are aggressive lymphomas, with the exception of some forms of CTCL. Aggressive PTCL subtypes include AITL, extranodal NK/T-cell lymphoma, PTCL-NOS, enteropathy-type T-cell lymphoma (EATL), and ALCL