[Extramedular plasmacytoma in the urinary bladder--unusual localization].

Background: Multiple myeloma is a plasmaproliferative disease characterized by the uncontrolled proliferation of a pathogenic plasma cell clone engaged in the production of monoclonal immunoglobulin. This condition affects the bone marrow, but it can be manifested in any other organ or tissue. The urinary bladder involvement is extremely rare.
Case Report: We reported a 70-year-old male with the history of multiple myeloma, receiving chemotherapy containing melphalan and prednisone (MP). Two years after the treatment, there was a renal failure associated with oligoanuria, hematuria and bilateral hydronephrosis. The urine cytology tests revealed the atypical cells, so was suspected obstructive uropathy to be caused by urothelium cancer. However, only upon the cystoscopy and biopsy performed on the urinary bladder mass, plasmacytoid infiltration diagnosis was confirmed. This extremely rare variant was presented throughout the illness period and proved to be resistant to the administered chemotherapy.
Conclusion: When renal failure associated with hematuria and bilateral hydronephrosis is presented in a patient with multiple myeloma, this unusual and rare extramedular localization should be also considered.