Introduction

The lymphomas are historically divided into non-Hodgkin's lymphoma and Hodgkin's disease. In 1998, there were approximately 57 000 cases of non-Hodgkin's lymphoma in the US, with about 7500 cases of Hodgkin's disease. The incidence of non-Hodgkin's lymphoma appears to be rising steadily at approximately 1% per year whereas the incidence of Hodgkin's disease appears to be stable or declining slightly.

The incidence of lymphoma does not seem to vary widely over racial subsets and geographic boundaries. There is growing evidence of association of the development of non-Hodgkin's lymphoma with organopesticides. Non-Hodgkin's lymphoma and to a lesser extent Hodgkin's disease does appear to be associated with some viral infections including human immunodeficiency virus (HIV), hepatitis B, and Epstein–Barr virus. As well, non-Hodgkin's lymphoma is associated strongly with intense immunosuppression usually given for solid organ transplantation. Such patients have a 10–1000-fold increase to incidence of lymphoma depending on the type and intensity of immunosuppression.

Anatomy and histology

Non-Hodgkin's lymphoma is usually a disease that involves lymph node tissues, spleen and, in later stages, bone marrow. Extranodal sites are also seen in non-Hodgkin's lymphoma. The most common extranodal sites are stomach, testis, CNS, and bone. The non-Hodgkin's lymphoma represents a spectrum of subtypes ranging from extraordinarily indolent diseases to some of the most explosive virulent malignancies known.

Hodgkin's disease is almost always a disease of nodal origin. Over 90% of the time the patients present with disease above the diaphragm, particularly cervical lymphadenopathy and mediastinal involvement.