Primary diffuse large B‐cell lymphoma of the ileal conduit created after radical cystectomy

INTRODUCTION: Creation of an ileal conduit is associated with complications. A few cases have been reported on tumor development in an ileal conduit; diffuse large B‐cell lymphoma originating from an ileal conduit is extremely rare. CASE PRESENTATION: A 62‐year‐old Japanese man who had undergone radical cystectomy and ileal conduit diversion 6 years previously presented with a whitish bulge that had developed on the surface of the ileal conduit during follow‐up visit. Mass biopsy was performed and the histological diagnosis was diffuse large B‐cell lymphoma. Positron emission tomography showed no metastatic lesions. We attempted chemotherapy because the tumor cells tested positive for CD20; after six courses of a regimen involving rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone; diffuse large B‐cell lymphoma of the ileal conduit resolved gradually. The patient is alive and remains free from the diagnosed diffuse large B‐cell lymphoma. CONCLUSION: We reported an extremely rare case of diffuse large B‐cell lymphoma originating from the ileal conduit created after radical cystectomy.