[A CASE OF MALIGNANCY ARISING IN A NEOBLADDER MORE THAN 50 YEARS AFTER RECONSTRUCTION].

A 75-year-old woman who had undergone right nephrectomy, total cystectomy, and orthotopic neobladder reconstruction using a free intestinal segment in 196X (precise diagnosis and surgical details unknown) presented with discomfort during urine storage and pain during urination. She was referred to our department in October 202Y, and urine cytology was positive. Magnetic resonance imaging revealed direct anastomosis of the free intestinal segment to the bladder neck, with a nodular tumor in the lumen. Cystoscopy revealed a nodular tumor with an abnormal surface vasculature inside the neobladder. No abnormalities were observed at the ureteral anastomotic site or remaining bladder neck-intestinal anastomosis. Retrograde urography revealed no upper urinary tract abnormalities. The tumor was diagnosed as a primary neobladder tumor. In December 202Y, the patient underwent open neobladder resection, including urethrectomy and hysterectomy, to create a left ureterocutaneous fistula. Pathological examination revealed adenocarcinoma of intestinal origin. Postoperatively, the patient was referred to the surgical department with a diagnosis of small intestinal cancer and continued chemotherapy.Adenocarcinoma may develop secondary to ureterocolonic anastomotic sites after ureterocolonic diversion. However, tumors arising within a free intestinal segment used for urinary diversion are rare. Here, we report the case of tumor development within a free ileal segment >50 years after neobladder reconstruction, along with a brief literature review.