Comparison of clinicopathologic characteristics of gastric follicular lymphomas and duodenal follicular lymphomas.

We compared the incidence, esophagogastroduodenoscopy (EGD) findings, and histopathologic characteristics of gastric and duodenal follicular lymphomas (FL). Of 626 FL cases, primary gastric FL and secondary gastric involvement of FL were observed in 1% and 5% of the cases, respectively, which were lower incidences than duodenal FL (10% and 9%, respectively). Gastric FL usually appeared as submucosal tumors (primary, 71%; secondary, 79%), whereas duodenal FL, as granular lesions (primary, 92%: secondary, 87%). In the granular duodenal lesions, the neoplastic follicles were located sparsely on the muscularis mucosa and could be found between villi, whereas in the stomach, similar lesions were hidden within the lamina propria, and only larger lesions such as submucosal tumors could be detected on the mucosal surface. The differences in the incidences and EGD findings were considered to be associated with structural differences of the lamina propria. Typical FL features: grades 1-2 histology, follicularity, and CD10+ and/or BCL6+ and BCL2+ were usually observed in all primary and secondary gastric and duodenal FL. Gastroduodenal and bone marrow involvement were found in 12% and 33% of the cases, respectively, and there was no significant correlation between them (P=.095). Twenty-nine cases (5%) were up-staged by gastroduodenal-positive results. In conclusion, the histopathology of gastric FL was similar to that of duodenal and nodal FL; the differences in the incidence and EGD findings between gastric and duodenal FL were considered to be associated with structural difference of the lamina propria, and EGD was useful as a staging procedure.