Differences in germinal centre and non-germinal center phenotype in gastric and intestinal diffuse large B-cell lymphomas.

The gastrointestinal tract is the most common extranodal site of lymphoma, and the most common gastrointestinal lymphoma is diffuse large B-cell type (DLBCL). DLBCL can be separated into germinal centre (GCP) and non-germinal centre phenotypes (non-GCP) using CD10, BCL-6 and MUM1 immunohistochemistry, but primary gastrointestinal DLBCL has not been extensively studied. We investigated 48 cases of primary gastrointestinal DLBCL (33% involving the small intestine, 50% the stomach, 13% the large intestine and 4% the ileocecal junction) and found that most (88%) DLBCL in the intestines were of GCP, while only 58% of gastric DLBCL were of GCP. This difference in GCP and non-GCP in gastric vs. intestinal DLBCL may be due to variations in lymphomagenesis reflecting acquired vs. native mucosa-associated lymphoid tissue. There was no significant difference in either overall survival or disease-free survival between the germinal centre and non-germinal centre groups. The distribution of Helicobacter pylori in different gastric DLBCL phenotypes raises interesting questions about the pathogenesis of H. pylori-associated lymphomas.