Lymphoma is a general term for a large group of blood cancers that affect white blood cells called lymphocytes. At present there are more than 70 such cancers, loosely categorized in four groups. Traditionally, these cancers were classified as either Hodgkin's lymphomas or non-Hodgkin's lymphomas, but these terms are being phased out.
Healthy lymphocytes are important components of the immune system. They help protect the body from disease caused by invasive organisms, such as viruses, fungi or bacteria. The lymphocytes are categorized as either large or small, and are further subdivided according to their particular functions and activities. Large lymphocytes include natural killer cells, while the small lymphocytes include T cells and B cells.
The Lymphatic System
Lymph nodes are small round or oval organs scattered throughout the body in locations such as the armpits, groin, and stomach. When lymphocytes grow uncontrollably or live beyond their natural lifespans, they may be classified as cancerous. In most cases, these abnormal cells form tumors at the lymph nodes. Each lymph node serves as a nexus for the lymphatic system, which consists of lymphatic fluid circulating through lymphatic vessels that are anatomically similar to blood vessels. Lymphatic fluid is similar to blood plasma; it is a nearly clear liquid composed primarily of water, with other components.
The lymphatic system parallels and is complementary to the circulatory system. Foreign invaders such as bacteria are carried via lymphatic fluid through the lymphatic vessels to the nearest lymph node, where they are destroyed. Other components of the lymphatic system—and potential sites of lymphoma—include the spleen, thymus, tonsils, adenoids, and bone marrow.
Lymphoma Warning Signs
Lymphoma symptoms include swelling of the affected node or nodes, with or without tenderness, and possible fever, unexplained weight loss, night sweats, chills, itching, and low energy. Although many of these symptoms are common to any number of illnesses, it is important to see a physician to rule out lymphoma if they persist.
Tumors may also occur in other organs. Lymphomas are divided into two types:
- Hodgkin lymphoma (HL; formerly known as Hodgkin's lymphoma), which is among the most curable of cancers. HL shares many similarities with NHL, however HL spreads in a more orderly manner than NHL, and is characterized by abnormal cells known as Reed-Sternberg cells (R-S cells).
- Non-Hodgkin lymphoma (NHL; formerly called non-Hodgkin's lymphoma). NHL comprises more than a dozen distinct diseases that are only loosely related to one another. Various systems have been proposed to classify the various forms of lymphoma. Today, most types of tumors are broadly characterized according to the type of lymphatic cell they derived from: T cell, B cell, or natural killer cell.
Categories for lymphoma are generally classified as either aggressive (fast-growing) or indolent (slow-growing). Depending on the type of symptoms presented, categories may be further split to include:
- E: Spreading of lymphoma to an organ or other area of the body
- S: Spreading of lymphoma to the spleen
Prognosis for many forms is good but depends on prompt and accurate diagnosis followed by appropriate treatment. Diagnosis is accomplished by taking a sample of affected tissue (biopsy) and identifying the cells through microscopic examination and other differentiation techniques. Treatment may consist of "watchful waiting," chemotherapy or radiation (or both), bone marrow or stem cell transplantation, and/or immunotherapy (also known as biological therapy). Some low-grade lymphomas are incurable, but survivable.