Hodgkin’s disease is a type of lymphoma, or cancer of the lymphoid tissue. Lymphoid tissue is part of the lymphatic system. A major component of the immune system, the lymph system consists of organs, lymph nodes and vessels. The lymphatic system is responsible for manufacturing and transporting lymph (fluid made of plasma and white blood cells) from tissues to the bloodstream.

Although Hodgkin’s lymphoma can start almost anywhere, it usually begins in the lymph nodes. In some instances, it can start in patches of lymphatic tissue in organs such as the stomach or intestines. Lymph nodes are small, bean-shaped organs located in groups in various areas of the body, including the neck, armpit, chest and groin. Their functions include producing immune cells (e.g., lymphocytes and plasma cells), and filtering bacteria, cancer cells and other foreign material from lymph. When the lymph nodes recognize antigens or foreign materials in the lymph fluid, they respond by enlarging and producing additional white blood cells. These white blood cells, which include lymphocytes and antibodies, help combat a variety of external threats.

The two types of lymphocytes are:

• B lymphocytes (B-cells). B-cells defend the body from invading bacteria and other harmful substances by changing into plasma cells, which produce antibodies. The antibodies then mark the antigens or foreign materials for destruction.
  
  
• T lymphocytes (T-cells). T-cells destroy antigens, infected and malignant cells directly.

As these abnormal cells continue to grow and expand, the lymph glands or other organs in which the lymphocytes grow begin to enlarge. The cells form lumps which begin to develop in the body. Organ function may become affected as the lymphocyte masses grow larger making it more difficult for normal cells to function.

Named after the physician who first identified it in 1832, Hodgkin’s lymphoma spreads through the lymph vessels to neighboring lymph nodes. The disease may spread to other areas of the body including the liver, bone marrow, spleen or lungs through the lymphatic system or the bloodstream.

The other main form of lymphoma is non-Hodgkin’s lymphoma (NHL). Hodgkin’s lymphoma can usually be distinguished from NHL when tissue is examined under a microscope. The characteristic cells found in Hodgkin’s lymphoma, known as Reed-Sternberg cells, are named after the physicians who first described them in detail. Many researchers believe that Reed-Sternberg cells are a form of malignant B-cells. Hodgkin’s lymphoma is less common than NHL.

According to the National Institutes of Health (NIH) the incidence of Hodgkin’s lymphoma is two in every 10,000 people. The disease occurs in both adults and children. However, it is most common in early adulthood (age 15 to 40, particularly ages 25 to 30) and late adulthood (after age 55). Only 10 to 15 percent of cases are diagnosed in children age 16 and younger. It is slightly more common in men than women.

The American Cancer Society (ACS) estimates that nearly 1,400 people will die of Hodgkin’s lymphoma in 2007. The five-year survival rate for all Hodgkin’s lymphoma patients after treatment is 85 percent. At 10 years, the survival rate is 77 percent and at 15 years it is 68 percent. 

A number of factors, including the stage of the disease and the patient's general health, affect a patient's chance of survival. Death rates have fallen more than 60 percent since the 1970s due to advances in treatments. By 2001, the ACS estimates that more than 123,000 people had survived this disease.