A 42-year-old man visited our hospital complaining of secondary infertility. An abdominal ultrasonography screening incidentally revealed a protruding lesion in the bladder. As the lesion extended from the prostatic urethra and bladder neck, there was a possibility of ejaculation dysfunction after resection of the lesion. Therefore, with the patient's informed consent, sperm cryopreservation was conducted for fertility preservation, and subsequently histological examination was performed by partial transurethral resection of bladder tumor. The pathological findings were proliferative cystitis including all three subtypes (glandularis, cystica, and papillary). Cyclooxygenase-2 immunostaining was positive in cytoplasm; weakly positive in cystic and papillary lesions, and strongly positive in glandular lesions. According to a literature review of massive proliferative cystitis, the patient was the 77th case in Japan. Novel postoperative immunological pharmacotherapies with cyclooxygenase-2 inhibitors have been introduced in recent years.