Gastrointestinal lymphomas: an overview with emphasis on new findings and diagnostic problems.

The first section of this article summarizes the salient clinicopathologic features of the more common types of primary gastrointestinal lymphomas, the recent explosion of information on the low grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), and new findings on multiple lymphomatous polyposis and ulcerative jejunitis. The second section discusses the practical problems that may be encountered in the diagnosis of gastrointestinal lymphomas, including diagnosis of large cell malignancies, distinction between lymphoma and reactive lymphoid hyperplasia, classification of diffuse small B-cell lymphomas (including the potential pitfall of mistaking Burkitt's lymphoma for small B-cell lymphoma), recognition of large cell transformation in low-grade B-cell MALT lymphoma, assessment of gastric biopsies from MALT lymphoma patients after anti-Helicobacter therapy, and assessment of nodal or splenic involvement in low-grade MALT lymphoma.