Malignant lymphoma in the gastrointestinal tract.

The main function of gut-associated lymphoid tissue is to provide an adaptive protective mechanism to help defend the body from exogenous antigen. This complex function requires the coordination of various cellular elements, including B cells, T cells, macrophages, and the epithelial cells of the gut. The control of this remains poorly defined, but involves various cellular subpopulations, humoral factors acting by autocrine and paracrine means, and cell adhesion molecules regulating tissue tropisms. Disruption of these cybernetic mechanisms is likely to be fundamental to the development and behavior of gut lymphomas. Although conventional histopathology is likely to remain the mainstay of diagnosis and patient management, further advances in the understanding, diagnosis, and therapy of gut lymphomas will require a greater knowledge of the cells and molecules that regulate the lymphoid milieu of the gut.