Clonally distinct diffuse large B-cell lymphoma developed in the residual ileum 12 years after resection: A case report

BACKGROUNDSmall intestinal lymphoma is considered a rare disease, and late relapse of diffuse large B-cell lymphoma (DLBCL) occurring more than 10 years after achieving a complete remission (CR) is also unusual.Based on immunohistochemistry, DLBCL can be classified into the germinal center B-cell (GCB) subtype and the non-GCB subtype.We report a case of DLBCL that developed in the residual ileum 12 years after the patient achieved a CR following partial bowel resection and chemotherapy.In both instances, the lymphoma lesions were found only in the small intestine. CASE SUMMARYA 51-year-old man was diagnosed with primary small bowel DLBCL (GCB type) following symptoms of intestinal obstruction.He initially underwent an ileal resection and subsequently received six cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) for a residual duodenal lesion, achieving a CR.Twelve years later, at the age of 63, the patient presented again with symptoms of intestinal obstruction.After surgical resection of the ileal lesion, the pathological diagnosis was non-GCB type DLBCL.Using the polymerase chain reaction singlestrand conformation polymorphism method, it was revealed that the initial lymphoma and relapsed lymphoma was consistent with distinct clonality.Despite the relapsed lymphoma being a double-expressor (c-MYC+ and BCL2+) and p53+, the patient achieved a CR with surgical resection and chemotherapy with polatuzumab vedotin.He has remained free of recurrence for more than 2 years. CONCLUSIONThis case is rare and suggestive because clonally distinct episodes of DLBCL developed exclusively in the small intestine, separated by a 12-year interval. / 22