Abstract: Objective To investigate the clinicopathological characteristics of duodenal⁃type follicular lymphoma (FL) and enhance awareness and diagnostic accuracy among clinicians and pathologists. Methods Analyzed the 15 cases of duodenal⁃type FL and reviewed pertinent literature to summarize the clinical manifestations, endoscopic features, pathological characteristics, and diagnosis essentials. Results This clinically atypical condition is typically an incidental endoscopic finding, with lesions primarily in the descending duodenum. Endoscopically, they appeared as white granular or nodular lesions (diameter range: 0.1-1.0 cm), with one polypoid case. Histologically, lesions were well⁃defined, exhibited expansile nodules of germinal centers within the mucosa and submucosa. The germinal centers were composed predominantly of centrocytes with scant centroblasts, showing low⁃grade follicular lymphoma (FL). Immunohistochemistry revealed diffuse BCL⁃2 expression in abnormal follicles, consistent with classic FL. Fluorescence in situ hybridization demonstrated t (14;18)(q32;q21) translocation. Next⁃generation sequencing revealed abnormal alterations in genes such as BCL⁃2, KMT2C, MET, CREBBP, BCL7A and IDH2. With a median follow⁃up of 18 months, all patients remained progression⁃free without chemotherapy, with spontaneous regression observed in 3 cases. Conclusion Duodenal⁃type FL exhibits a unique clinicopathological features, typically presenting as granular duodenal lesions, low⁃grade histology, and a favorable prognosis. 

Key words:  , Follicular lymphoma, Duodenum, Immunohistochemistry, Next generation sequencing, Prognosis