[A case of primary mucosa-associated lymphoid tissue-type lymphoma of the urinary bladder that progressed after antibiotic therapy].

We report a case of primary mucosa-associated lymphoid tissue (MALT)-type lymphoma of the urinary bladder, which temporarily regressed after antibiotic therapy and progressed 1 year after the treatment. The patient was a 72-year-old female with a history of recurrent cystitis. She was referred to our hospital for microscopic hematuria. Urinalysis also showed microscopic pyuria and cystoscopy revealed an erythematous and edematous submucosal lesion in the right side wall of the bladder. She was diagnosed with acute cystitis and treated with antibiotics. Cystoscopy after 2 months was normal. However, she presented with macroscopic hematuria and fever 1 year after the treatment. Computed tomography (CT) scan showed a solitary mass measuring 25×40 mm above the right ureteric orifice and right hydronephrosis. Transurethral resection was performed, and the histopathological findings were consistent with MALT-type lymphoma. No evidence of lymphoma was found on positron emission tomography-CT scan and bone marrow biopsy, and she was diagnosed with primary MALT-type lymphoma of the bladder. She was successfully treated with a combination of rituximab and radiotherapy. Since MALT-type lymphoma of the bladder sometimes regresses temporarily after antibiotic therapy, it should be followed carefully.