Hodgkin's disease

Definition

Hodgkin's disease is a type of cancer involving tissues of the lymphatic system. There are a variety of cancers, called lymphomas, that can affect lymph tissue. 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.

Description

Hodgkin's lymphoma can occur at any age, although the majority of these lymphomas occur in people between the ages of 15-34, and after the age of 60. An understanding of the lymphatic system, as well as a general understanding of the nature of cancer, is helpful in making sense out of Hodgkin's disease.

The lymphatic system

The lymphatic system is part of the body's immune system. It consists of a number of elements:

• A network of vessels which serve to 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 which serve to filter the lymph fluid, trapping foreign substances, including viruses, bacteria, and cancer cells, as well as any other encountered debris. (For example, lymph nodes which receive fluid from the lungs of city dwellers often contain gritty, dark material due to filtering of debris from polluted city air.)
• 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.
• Clusters of scavenger-like immune cells 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

Cancer is 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; that is, they acquire specific characteristics which ultimately allow liver cells to function as liver cells, blood cells as blood cells, brain cells as brain cells, etc. Cancer, then, is sometimes considered to be a process of de-differentiation, during which a type of cell loses its individuality and becomes 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: rapid multiplication of cells, abnormal cell types, loss of normal arrangement of cells with respect to each other, and invasive ability.

Causes & symptoms

Hodgkin's lymphoma usually begins in a lymph node. This node enlarges; but may or may not cause any pain--as would enlarged lymph nodes due to infectious causes. Hodgkin's lymphoma progresses in a fairly 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. They include fever, weight loss, heavy sweating at night, and itching. Some patients note pain after drinking alcoholic beverages.

As nodes swell, they may push on other nearby structures, resulting in 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 which carry urine from the kidneys to the bladder. The face, neck, or legs may swell due to pressure slowing the flow in veins which 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.

Diagnosis

As with many forms of cancer, diagnosis of Hodgkin's disease has two important components:

• The identification of Hodgkin's lymphoma as the cause of the patient's disease.
• The staging of the disease. Staging 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 very characteristic cells--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 which 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 scans (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. On the one hand, 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. On the other hand, all the available treatments have serious side effects. The goal of staging, then, is to allow the patient to have the type of treatment necessary to achieve a cure, but to minimize the severity of short and long-term side effects from which the patient may suffer.

Treatment

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 which kill cancer cells).

Both chemotherapy and radiotherapy have unfortunate 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 have 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--often called second malignancy. These second cancers might be 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.

Prognosis

Hodgkin's is one of the most curable forms of cancer. Current treatments are quite effective. Children have a particularly high rate of cure 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.

Key Terms

Biopsy

The removal of a small sample of tissue, in order to carefully examine it under a microscope. This helps in the diagnosis of cancer, and also can reveal infection or inflammation.

Chemotherapy

Treatment for a disease involving various chemical or drug preparations; this term tends in particular to refer to treatment for forms of cancer.

Constitutional

Involving the whole body. A constitutional symptom, for example, is one that is not focused entirely in the diseased organ system, but affects the whole system (such as fever).

Radiotherapy

Treatment for a disease involving carefully measured exposure to radiation.

Staging

Using various methods of diagnosis to determine the extent of disease present in an individual. Staging is important as a way of determining the appropriate type of treatment for a particular disease, as well as helping to predict an individual's chance for cure from a particular disease.

Further Reading

For Your Information

Books

• Dollinger, Malin, et al. Everyone's Guide to Cancer Therapy. Kansas City: Andrews McKeel Publishing, 1997.
• Freedman, Arnold S., and Lee M. Nadler. "Hodgkin's Disease." In Harrison's Principles of Internal Medicine, edited by Anthony S. Fauci, et al. New York: McGraw-Hill, 1998.
• Murphy, Gerald P., et al. Informed Decisions. New York: Viking, 1997.

  Periodicals

• Stoval, Ellen. "A Cancer Survivor Discusses Her Experiences." Washington Post 118 (February 14, 1995): WH15+.

  Organizations

• The Lymphoma Research Foundation of America, Inc. 8800 Venice Boulevard, Suite 207, Los Angeles, CA 90034. (310) 204-7040). http://www.lymphoma.org.

Gale Encyclopedia of Medicine. Gale Research, 1999.