life-threatening if appropriate therapy is not begun quickly. Cancer of the lymphoid system was first described by British physician Thomas Hodgkin, in 1832. The form he described behaves in a very predictable way and has come to be called Hodgkin's disease. Despite their diversity, all of the other malignant lymphomas are referred to as non-Hodgkin's lymphomas (NHL).
Types There are two main types of cells in the lymphoid system—B cells, which make antibodies in response to infection, and T cells, which are responsible for the regulation of the immune system . Both B cell and T cell lymphomas occur, but the vast majority of lymphomas in the U.S. are of B cell origin.
Whatever the origin, the features that best predict the prognosis and guide decisions about therapy are the size, shape and pattern of the lymphocytes as seen under the microscope. Malignant lymphocytes may be small and round or angulated (cleaved). Others may be large. Combinations of small and large cells may also be seen. Intermediate-sized lymphocytes with rapidly dividing cells are characteristic of aggressive (high-grade) lymphomas.
Within normal lymph nodes there are microscopic clusters (follicles) of specialized lymphocytes. In some malignant lymphomas, the lymphocytes arrange themselves in a similar pattern that is called follicular or nodular. Small cell and follicular lymphomas typically have a chronic course with an average survival of 6 to 12 years. In the more aggressive lymphomas, the normal appearance of the lymph node is lost by diffuse involvement of tumor cells, which are usually moderate-sized or large.
