OBJECTIVE:

Follicular lymphomas (FLs) occur commonly in the lymph nodes, and duodenal FL (DFL) is reported to be rare.

METHODS:

We analysed the clinical, morphological, immunohistochemical and genetic features of 26 cases of DFL. Primary DFLs and systemic FLs that involved the duodenum at any point during the clinical course were included in the analysis.

RESULTS:

Typically, primary DFLs (14 cases) were found incidentally at routine medical check-ups, whereas involvement of the duodenum by systemic FLs (12 cases) was found through staging procedures. All cases involved the second portion of the duodenum. Helicobacter pylori infection was common (71%). In all cases, the histologic grade was low (either grade 1 or 2), and CD20, CD10 and Bcl-2 were positive by immunohistochemistry. Immunoglobulin heavy chain gene (IGH) and bcl-2 gene (BCL2) fusion was frequently shown by fluorescence in situ hybridization (FISH) analysis: nine of 12 cases (75%) of primary DFL and 10 of 12 cases (83%) of systemic DFL were positive. Treatment regimens employed were rituximab (R) plus chemotherapy (10), R (6), chemotherapy (3), irradiation (3) and the other three patients were subjected to observation. After a median follow-up duration of 40 months (ranging 11-96 months), 17 patients were alive without disease, seven were alive with disease and one had died of lymphoma.

CONCLUSIONS:

Primary DFLs resemble systemic and nodal FLs, except that the former has high incidence of early stage and low-grade histology. The duodenum appears to be a frequently involved extranodal site of FL with IGH/BCL2.