I.

Introduction

Lymphoma, group of cancers that arise in the lymphatic system, body tissues that fight infection and perform several other vital functions in the body. Lymphoma is often called non-Hodgkin’s lymphoma to distinguish it from Hodgkin’s disease, a specific type of cancer that also affects the lymphatic system. However, the term non-Hodgkin’s lymphoma is somewhat misleading because, unlike Hodgkin’s disease, lymphoma encompasses many cancers. These various types of lymphoma differ from each other in symptoms, treatment, and prognosis, depending on the type of cell that becomes cancerous and other characteristics. According to the American Cancer Society, in 2005 more than 56,000 people in the United States developed lymphoma and 19,200 died of the disease. For reasons scientists do not completely understand, the number of people diagnosed with lymphoma has increased more than 80 percent since the early 1970s. The incidence of lymphoma increases with age, and it is slightly more prevalent among men than among women. In the United States, non-Hispanic whites have the highest incidence of lymphoma.