Hodgkin’s disease is a type of cancer involving tissues of the lymphatic system. The lymphatic system is a network of organs, tissues, and ducts in the human body. The lymphatic system maintains the fluid balance in the body by coordinating the draining of fluid from cells and tissues back into the bloodstream. Also, the lymphatic system aids in fighting infections caused by microorganisms, by supplying the body with white blood cells.
A variety of cancers called lymphomas affect the lymph tissues. Hodgkin’s disease represents a specific type of lymphoma. Its cause is unknown, although some interaction between individual genetic makeup, environmental exposures, and infectious agents is suspected.
Hodgkin’s lymphoma can occur at any age. The majority of all cases of Hodgkin’s lymphoma occur in people between the ages of 15 and 34 years, and those who are older than 60 years of age. The American Cancer Society (ACS) stated that in 2005 about 7,350 new cases of Hodgkin’s disease were diagnosed in the United States, with about 3,370 occurring in women and 3,980 in men. The statistics in the near past have remained relatively consistent with the numbers seen in 2005. The death rate has fallen by more than 60% since the early 1970s, primarily due to advances in medical treatments of the disease.
Examples of the syndrome were first recorded by Italian physician and physiologist Marcello Malpighi (1628–1694), in 1666, but it was an English physician, Thomas Hodgkin (1798–1866), who first described the disease in detail in 1832.
Born in London, England, in 1798, Hodgkin received his medical degree in 1821 from the University of Edinburgh and served as lecturer on morbid anatomy at Guy’s Hospital in London from 1825 to 1837. Hodgkin introduced the use of the newly invented stethoscope to Great Britain from the European continent and promoted the importance of postmortem examination. Passed over for an appointment as assistant physician at Guy’s Hospital, Hodgkin, a Quaker, devoted increasing amounts of time in his later years to philanthropic and humanitarian concerns. He died of dysentery in Jaffa on a mission to Palestine in 1866.
Hodgkin’s interest in postmortem investigations led to the presentation of a paper in 1832 titled “On Some Morbid Appearances of the Absorbent Glands and Spleen,” describing a particular type of lymphoma characterized by swollen lymph tissue. The importance of this paper was not recognized until 1856, when English physician and biographer Samuel Wilks (1824–1911) described the condition and named it Hodgkin’s disease.
The lymphatic system is part of the body’s immune system. It consists of a number of elements. First, there is a network of vessels. The vessels drain tissue fluid from all the major organs of the body, including the skin, and from all four limbs. These vessels pass through lymph nodes on their way to empty their contents into major veins at the base of the neck and within the abdomen.
The lymph nodes are clusters of specialized cells that serve to filter the lymph fluid. In this capacity, they trap foreign substances such as viruses, bacteria, cancer cells, as well as any other encountered debris. For example, the examination of lymph nodes from people who live in large, industrialized cities typically detects gritty, dark material, which is not present in the lymph nodes of people who live in rural settings. This is because the lymph nodes of the city dweller have received fluid from the lungs, which contain debris from polluted city air.
Another component of the lymphatic system are lymphocytes. Lymphocytes are cells of the immune system. They are produced within bone marrow, lymph nodes, and spleen, and circulate throughout the body in both blood and lymph fluid. These cells work to identify and rid the body of any invaders that threaten health.
Still another component of the lymphatic system are clusters of scavengerlike immune cells. These exist in major organs, and provide immune surveillance on location. These include the tonsils and adenoids in the throat/pharynx, Kupffer cells in the liver, Peyer’s patches in the intestine, and other specialized immune cells stationed in the lungs and the brain.
Cancer is a general term that refers to a condition in which a particular type of cell within the body begins to multiply in an out-of-control fashion. This may mean that cancer cells multiply more quickly, or it may mean that cancer cells take on abnormal characteristics. For example, at a very early stage in embryonic development (development of a fetus within the uterus), generic body cells begin to differentiate. Cells acquire specific characteristics that ultimately allow liver cells to function as liver cells, blood cells as blood cells, brain cells as brain cells, and so on. Thus, cancer can be considered a process of de-differentiation. In other words, a specialized type of cell loses whatever controls govern the expression of its individual characteristics and instead revert to a more embryonic cell. Such cells also lose their sense of organization and no longer position themselves appropriately within their resident tissue.
Cancer cells can also acquire the ability to invade other tissues. Normally, for example, breast cells are found only in breast tissue. However, cancerous breast cells can invade into other tissue spaces, so that breast cancer can spread to bone, liver, brain, etc.
Lymphoma is a cancer of the lymph system. Depending on the specific type, a lymphoma can have any or all of the characteristics of cancer. These characteristics include rapid multiplication of cells, abnormal cell types, loss of normal arrangement of cells with respect to each other, and invasive ability.
Hodgkin’s lymphoma usually begins in a lymph node. This node enlarges, but may or may not cause the pain that typically results when lymph nodes enlarge because of an infection by a microorganism. Hodgkin’s lymphoma progresses in a predictable way, traveling from one group of lymph nodes on to the next. More advanced cases of Hodgkin’s include involvement of the spleen, the liver, and bone marrow.
Constitutional symptoms (symptoms which affect the whole body) are common, and include fever, weight loss, heavy sweating at night, and itching. Some patients note pain after drinking alcoholic beverages.
As the lymph nodes swell, they may push on other nearby structures. This pressure produces other symptoms. These symptoms include pain from pressure on nerve roots, as well as loss of function of specific muscle groups served by the compressed nerves. Kidney failure may result from compression of the ureters, the tubes that carry urine from the kidneys to the bladder. The face, neck, or legs may swell due to pressure slowing the flow in veins that should drain blood from those regions (superior vena cava syndrome). Pressure on the spinal cord can result in paralysis of the legs. Compression of the trachea and/or bronchi (airways) can cause wheezing and shortness of breath. Masses in the liver can cause the accumulation of certain chemicals in the blood, resulting in jaundice (a yellowish discoloration of the skin and the whites of the eyes).
As Hodgkin’s lymphoma progresses, a patient’s immune system becomes less and less effective at fighting infection. Thus, patients with Hodgkin’s lymphoma become increasingly more susceptible to both common infections caused by bacteria and unusual (opportunistic) infections caused by viruses, fungi, and protozoa.
The exact cause of Hodgkin’s disease is not known. Viruses, particularly the Epstein-Barr virus (a herpes virus that causes infectious mononucleosis), are found in tissues of 20–50% of people with Hodgkin’s disease. However, a link between the virus and Hodgkin’s disease has not been established.
Another suggested cause is socioeconomic conditions. Studies have demonstrated that Hodgkin’s disease is more prevalent in wealthier people in the developed world. It has been speculated that the hygienic conditions that most of these people grow up in does not stress their immune systems in a way that is healthy for them. Other suggested causes include exposure to chemicals, and a genetic disposition (including the activity of cancerous genes known as oncogenes).
As with many forms of cancer, diagnosis of Hodgkin’s disease has two important components. First is the identification of Hodgkin’s lymphoma as the cause of the patient’s disease. Second is the staging of the disease; that is, an attempt to identify the degree of spread of the lymphoma.
Diagnosis of Hodgkin’s lymphoma requires removal of a sample of a suspicious lymph node (biopsy) and careful examination of the tissue under a microscope. In Hodgkin’s lymphoma, certain characteristic cells, which are called Reed-Sternberg cells, must be present in order to confirm the diagnosis. These cells usually contain two or more nuclei. The nucleus is the oval, centrally located structure within a cell that houses the genetic material of the cell. Reed-Sternberg cells also have other unique characteristics, which cause them to appear under the microscope as owl’s eyes or yin-yang cells. In addition to the identification of these Reed-Sternberg cells, other cells in the affected tissue sample are examined. The characteristics of these other cells help to classify the specific subtype of Hodgkin’s lymphoma present.
Once Hodgkin’s disease has been diagnosed, staging is the next important step. This involves computed tomography (CT) scans of the abdomen, chest, and pelvis, to identify areas of lymph node involvement. In rare cases, a patient must undergo abdominal surgery so that lymph nodes in the abdominal area can be biopsied (staging laparotomy). Some patients have their spleens removed during this surgery, both to help with staging and to remove a focus of the disease. Bone marrow biopsy is also required unless there is obvious evidence of vital organ involvement. Some physicians also order lymphangiograms (a radiograph of the lymphatic vessels).
Staging is important because it helps to determine what kind of treatment a patient should receive. It is important to understand the stage of the disease so that the treatment chosen is sufficiently strong to provide the patient with a cure. All available treatments, however, have potentially serious side effects. The goal of staging, then, is to allow the patient to have the type of treatment necessary to achieve a remission, but to minimize the severity of short- and long-term side effects from which the patient may suffer.
Treatment of Hodgkin’s lymphoma has become increasingly effective over the years. The type of treatment used for Hodgkin’s depends on the information obtained by staging, and may include chemotherapy (treatment with a combination of drugs), and/or radiotherapy (treatment with x rays that kill cancer cells).
Both chemotherapy and radiotherapy often have side effects. Chemotherapy can result in nausea, vomiting, hair loss, and increased susceptibility to infection. Radiotherapy can cause sore throat, difficulty swallowing, diarrhea, and growth abnormalities in children. Both forms of treatment, especially in combination, can result in sterility (the permanent inability to produce offspring), as well as heart and lung damage.
The most serious negative result of the currently available treatments for Hodgkin’s disease is the possible development in the future of another form of cancer. This phenomenon is referred to as second malignancy. Examples of second cancers include leukemia (cancer of a blood component), breast cancer, bone cancer, or thyroid cancer. A great deal of cancer research is devoted to preventing these second malignancies.
Hodgkin’s is one of the most curable forms of cancer. Current treatments are quite effective. Children have a particularly high cure rate from the disease, with about 75% still living cancer-free 20 years after the original diagnosis. Adults with the most severe form of the disease have about a 50% cure rate.
See also Genetic disorders.
Jaffe, E.S., N.L. Harris, H. Stein, et al. Pathology and Genetics of Tumours of the Haematopoietic and Lymphoid Tissues. Lyon: IARC Press, 2001.
The Leukemia and Lymphoma Society (LLS). “Home page of LLS.” <http://www.leukemia-lymphoma.org.> (accessed October 11, 2006).