Purine analogs in marginal-zone lymphomas.

In an area of lymphoma classification still being defined, marginal-zone lymphomas have distinctive immunohistochemical and cytogenetic features that distinguish them from mantle-cell and follicular lymphomas. There are three subtypes: the extranodal mucosa-associated lymphoid tissue (MALT) lymphomas, the nodal monocytoid B-cell (MBCL) lymphomas, and the splenic marginal-zone lymphomas. The MALT lymphomas represent the neoplastic counterpart of the gut-associated lymphoid tissue, which extends from the jejunum to the rectum. They arise in sites usually containing no lymphoid tissue, such as the stomach, thyroid, and salivary gland. Gastric MALT lymphomas, the most common, are associated with Helicobacter pylori. The MBCL lymphomas closely resemble MALT lymphomas and unlike other non-Hodgkin's lymphomas are commonly composite. Therapy for these lymphomas may include radiation therapy or surgery when disease is of limited extent. However, gastrectomy for gastric MALT lymphomas is not in favor because of the efficacy of antibiotic regimens that can eliminate H. pylori infection. Splenectomy may be indicated for splenic lymphomas. Purine analogs are promising therapeutic agents because they are specific for lymphoid cells. Also, they may prove useful in indolent cancers such as these, because of their activity against dividing and resting cells. Purine analogs may be considered as second-line therapy after alkylating agents for these lymphomas.