Primary malignant lymphomas of the bladder are infrequent. We report a 70 year old woman presenting with hematuria, dysuria, malaise and a 5 kg weight loss. Pelvic ultrasound examination showed a 8 x 8 x 8 cm solid and cystic mass adjacent to the bladder and uterus. Cystoscopic biopsy disclosed a low grade B cell non Hodgkin lymphoma. She was treated with 6 cycles of chemotherapy with disappearance of the mass. Two years after admission, the patient is free of disease.