Overview

Non-Hodgkin's lymphoma is a group of cancers that originate in the lymphatic system, the lymph nodes, vessels, and organs that produce infection-fighting and tumor-fighting cells and carry them throughout the body.

About 53,000 people in the United States are diagnosed with non-Hodgkin's lymphoma each year. Non-Hodgkin's lymphoma is much more common in adults than children and is now the fifth most common cancer among both men and women. The number of new cases of non-Hodgkin's lymphoma diagnosed each year has nearly doubled over the past 30 years, with much of the increase occurring among patients over the age of 60.

The Lymphatic System

The organs and tissues that make up the lymphatic system include the lymph nodes, thymus, spleen, tonsils and adenoids, bone marrow, and tissues in the gastrointestinal tract. Lymph (clear fluid from these tissues) contains proteins, immune cells, and waste products, and travels throughout the body in the lymphatic vessels of this system. Lymphatic tissues produce white blood cells called lymphocytes, of which there are three kinds: B lymphocytes (or B cells), T lymphocytes (or T cells), and natural killer (NK) cells. Each of these types of cells performs a unique job in the battle against infectious agents and cancer, targeting a very particular range of pathogens.

How Lymphomas Arise

Non-Hodgkin's lymphoma arises when a B cell, T cell, or NK cell undergoes a transformation from a normal cell into a malignant cell, one capable of uncontrolled growth and spread. The malignant cell begins producing identical copies of itself, or clones, in the lymphatic tissue. Over time these malignant cells can spread to neighboring groups of lymph nodes or tissues, and if not treated, may spread to other parts of the body.

The majority of non-Hodgkin's lymphomas develop from B cells. These lymphocytes progress through a number of different stages; lymphoma can develop at each stage, and each stage is associated with a particular malignancy with its own specific behavior.

Types of Non-Hodgkin's Lymphoma

Non-Hodgkin's lymphoma is actually a complex group of almost 40 distinct entities. After determining that a patient has non-Hodgkin's lymphoma, physicians classify his or her disease, or distinguish its type, and stage the disease -- discover if and how far it has spread from its site of origin. This information is crucial in selecting the most effective treatment and delineating the patient's prognosis, or outlook.

Physicians use a classification system for non-Hodgkin's lymphoma that has evolved as understanding of the disease has progressed. The current system is called the WHO/REAL system (for World Health Organization/Revised European American Lymphoma classification), and it allows physicians to distinguish lymphomas based on a number of characteristics: the appearance of the cells, their genetic features, their chemistry, and their clinical behavior.

Although there are many forms of non-Hodgkin's lymphomas, the 13 most common types account for 88 percent of the cases in the United States. The most common form, diffuse large B-cell lymphoma, comprises 31 percent and follicular lymphoma comprises 22 percent. Four other lymphomas -- small lymphocytic lymphoma, mantle-cell lymphoma, peripheral T-cell lymphoma, and marginal zone B-cell lymphoma MALT-type -- each account for 5-6 percent of cases. The other types each make up less than 2 percent of cases.

About 25 other, very rare forms of non-Hodgkin's lymphoma are seen relatively frequently at Memorial Sloan-Kettering, owing to our large patient base and large number of referrals for these very unusual forms of the disease.

Physicians also divide all types of non-Hodgkin's lymphoma into two groups, indolent lymphomas, which grow more slowly and have fewer symptoms, and aggressive lymphomas, which grow more quickly. Patients with indolent lymphomas may be without symptoms for several years, but these non-Hodgkin's lymphomas are more difficult to cure than the aggressive forms of the disease. Aggressive lymphomas can quickly lead to death if not treated, but in general are more curable. Indolent lymphomas account for approximately 40 percent of new diagnoses; aggressive lymphomas account for about 60 percent.