Fig. 1. Study flow chart.

Fig. 2. Endoscopic, radiological, and pathological findings of case no. 1. (A) Multiple white nodular lesions are observed near the ampulla of Vater. (B) A hypermetabolic lymph node is identified in the bowel mesentery, just above the aortic bifurcation (arrow). (C) Pathological findings show neoplastic follicles in the duodenal mucosa (hematoxylin and eosin stain, ×50) and immunohistochemical staining positive for CD21, positive for BCL-2, and with a low Ki-67 proliferation index (immunohistochemistry, ×50).

Fig. 3. Endoscopic, radiological, and pathological findings of case no. 3. (A) Multiple white polypoid mucosal lesions, approximately 0.2 cm in size, are observed in the second portion of the duodenum. (B) Abdominal computed tomography reveals lymph node enlargement in the right common iliac and right inguinal areas (arrow). (C) Hypermetabolic lymph nodes are noted in the bilateral axilla, right common iliac, bilateral external iliac, and bilateral inguinal to femoral areas (arrow). (D) Pathological findings show neoplastic follicles in the duodenal mucosa (hematoxylin and eosin stain, ×50) and immunohistochemical staining positive for CD21, diffusely positive for BCL-2, and with a low Ki-67 proliferation index (immunohistochemistry, ×50).