A 29-year-old woman had undergone gastrocystoplasty with Mitrofanoff appendicovesicostomy for urethral trauma at 9 years of age. Since then, she was being followed up for performing clean intermittent self-catheterization at regular intervals. Twenty years after the surgery, she presented with gross hematuria. Ultrasonographic findings revealed bilateral hydronephrosis. Cystoscopy and computed tomography (CT) revealed invasive bladder cancer with pelvic lymph node metastases. A biopsy confirmed the diagnosis of adenocarcinoma with signet ring cell carcinoma. Subsequently, neo-adjuvant combination chemotherapy with TS-1 and cisplatin (CDDP) was initiated, which was followed by open radical cystectomy with extended pelvic lymphadenectomy. The tumor was found to infiltrate from the anastomotic site into the entire native bladder and histopathological diagnosis was muscle invasive adenocarcinoma with neuroendocrine differentiation and lymph node metastasis (ypT3bN2). TS-1 was continued as adjuvant chemotherapy and the patient did not have any evidence of recurrence for 12 months postoperatively.