Primary bladder diffuse large B-cell lymphoma causing unilateral ureterovesical junction obstruction: A case report

: Primary bladder diffuse large B-cell lymphoma is a rare extranodal malignancy that often mimics urothelial carcinoma. We report a 65-year-old male with flank pain and hematuria found to have a bladder mass extending to the ureterovesical junction with hydroureteronephrosis; urine cytology was repeatedly negative. Cystoscopic biopsy confirmed DLBCL, with no marrow involvement. Transurethral resection plus R-CHOP chemotherapy produced complete metabolic response on FDG-PET/CT, with stable residual uptake later deemed post-treatment change (Deauville 3). This case highlights ureteral obstruction as an unusual presentation and serial PET/CT as valuable for distinguishing residual lymphoma from fibrosis after therapy.