Primary urinary bladder marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue

Primary urinary bladder marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is an extremely rare disease. Here, we have reported a case of MALT lymphoma that was successfully treated with transurethral resection of the bladder tumor (TUR-BT) and radiotherapy. A 65-year-old woman presented with macroscopic hematuria. She had a history of chronic cystitis. Cystoscopy of the bladder revealed a submucosal tumor measuring 4 cm in the trigone of the bladder floor. Magnetic resonance imaging showed that the lesion had intermediate intensity on T2-weighted images. TUR-BT was performed, and the lesion was diagnosed with marginal zone B-cell lymphoma of MALT histopathologically. Positron emission tomography (PET) showed a slightly higher fluorine-18-deoxyglucose (FDG) accumulation, with a maximum standardized uptake value of 17.3, than the physiological accumulation in the tumor resection area of the bladder, with no obvious abnormal accumulation outside the bladder. The patient underwent field radiotherapy at a dose of 30 Gy in 15 fractions, administered in 5 fractions per week. She developed grade 2 cystitis as an acute radiation-related adverse event, without any hematological adverse events. On PET at 5 months after radiotherapy, FDG accumulation in the posterior wall of the bladder was obscured and remained regressed after 2 years.