BCL2-Negative Duodenal-Type Follicular Lymphoma Unmasked After Helicobacter pylori Eradication.

Duodenal-type follicular lymphoma (FL) is a rare extranodal variant of FL that is typically diagnosed incidentally and follows an indolent course. Most cases demonstrate BCL2 overexpression and the t(14;18) translocation. We report a rare case of BCL2-negative duodenal-type FL identified on surveillance endoscopy following eradication of Helicobacter pylori-associated lymphoid hyperplasia. Persistent duodenal nodularity prompted repeat biopsy, revealing grade 1-2 FL lacking BCL2 rearrangement on fluorescence in situ hybridization. Staging evaluation confirmed localized disease with a low Follicular Lymphoma International Prognostic Index score, and active surveillance was pursued. This case highlights an important diagnostic pitfall and underscores the need for repeat endoscopic evaluation, staging assessment, and comprehensive morphologic, immunophenotypic, and molecular analysis when duodenal lymphoid lesions persist despite treatment of inflammatory conditions.