Development of diffuse large B-cell lymphoma from follicular lymphoma of the duodenum: changes in endoscopic findings during a 6-year follow-up.

A 71-year-old Japanese man was diagnosed as having stage I primary follicular lymphoma (FL) of the duodenum according to Lugano International Conference Classification and began receiving annual checkups. Endoscopic examination disclosed white villi swelling with depressed red mucosal lesions. Biopsy specimens from the area of white villi exhibited histopathological features that met the diagnostic criteria for low-grade FL. The depressed red lesions gradually enlarged over six years of follow-up. A biopsy of the white villi swelling revealed distinct well-circumscribed follicles with attenuated mantles in the lamina propria that were positive for CD20, bcl-2, and CD10. Histological findings from the depressed red lesions at 5.5 years after the initial diagnosis were compatible for FL. However, biopsy specimens 6 months later obtained from the same lesions showed a mixture of larger mononuclear cells. These follicular cells were positive for CD20 and bcl-2, but not for CD10, indicating the presence of diffuse large B-cell lymphoma (DLBCL). This case shows altered endoscopic findings in the course of DLBCL development from FL. When depressed red lesions are detected in the background of white villi swelling, repeated biopsies should be performed from both lesions.