Duodenal-Type Follicular Lymphoma: A Newly Recognized Entity In The 2016 World Health Organization Classification Update

Abstract Introduction/Objective Most cases of primary follicular lymphoma (FL) in the gastrointestinal tract occur in the second part of the duodenum, presenting with multiple small polyps. Duodenal type follicular lymphoma (D-FL) is a newly recognized entity in the 2016 WHO classification update. Methods Upper endoscopy in a 72 year old female with iron deficiency anemia revealed a single 8 mm sessile polyp with no bleeding in the duodenal bulb. Histology revealed dense infiltrate of small mature lymphocytes with a nodular growth pattern. Follicles, composed predominantly of centrocytes with scattered centroblasts, diffusely expressed CD20, CD10 and BCL-2. Results This immunoprofile characterizes follicular lymphoma. Real-time polymerase chain restriction assay detected BCL-2 MBR/JH DNA fusion sequence, usually resulting from t(14;18)(q32;q21) translocation and confirming D-FL. D- FL is often asymptomatic, discovered incidentally at endoscopy. It is usually low grade (grade 1–2), presenting at low stage, with immunophenotype and t(14;18)(q32;q21) similar to other FLs. However, in comparison to nodal FL, D-FL has higher selective use of V4 and V5 immunoglobulin heavy chain gene rearrangements, which has been linked to antigen dependent mechanisms in lymphoma development; this feature is shared with Mucosa-Associated Lymphoid Tissue (MALT) lymphoma. Conclusion D-FL often remains localized to the small bowel and has a good outcome even with local small bowel recurrences. It has a long term survival of >12 years. There is a low (<10%) risk of progression to nodal disease and given the indolent clinical course, a watch-and-wait approach is reasonable for most patients.