Primary adenocarcinoma arising in an ileal neobladder is an exceptionally rare long-term complication following radical cystectomy. Chronic inflammation, recurrent infections, and prolonged exposure of intestinal mucosa to urine have been proposed as contributing factors. We report a rare case of intestinal-type adenocarcinoma arising in an ileal neobladder over 30 years after radical cystectomy.

A 70-year-old man presented with gross hematuria for two weeks. His medical history included muscle-invasive bladder cancer treated with radical cystectomy and ileal neobladder reconstruction over 30 years prior, after which he was lost to follow-up for two decades. Comorbidities included SLE and chronic thrombocytopenia. Urinalysis revealed microscopic hematuria. Abdominal CT showed no recurrence or lymphadenopathy. Cystoscopy in January 2024 revealed mucosal fragility near the bladder neck; urine cytology was negative. Bleeding was initially attributed to thrombocytopenia. The patient developed persistent urinary incontinence and recurrent UTIs. Despite Foley catheter and antibiotics, hematuria recurred. Repeat cystoscopy in February 2025 revealed necrotic tumor-like lesions at the neobladder anastomosis, prompting TURBT. Pathology confirmed intestinal-type adenocarcinoma with mucin pools and pleomorphic gland-forming cells, immunopositive for CK7, CK20, and CDX2, and negative for GATA3. Resection of the neobladder with ileal-conduit reconstruction was scheduled, but a firm supraumbilical nodule was discovered and incisional biopsy revealed metastatic adenocarcinoma. A Port-A catheter was implanted, and repeat TURBT was performed for tumor control and hemostasis. Chemotherapy with fluorouracil, oxaliplatin, and calcium folinate was initiated in March 2025.

Adenocarcinoma arising from an ileal neobladder is a rare but serious long-term complication. Diagnosis can be challenging due to non-specific symptoms such as hematuria, incontinence, and UTIs. These cases posed diagnostic difficulties due to altered anatomy, which limited the accuracy of radiological and cystoscopic evaluations. Pathology played a crucial role in confirming the origin of the tumor, differentiating it from urothelial carcinoma, new primary malignancies or metastatic lesions. Youn et al. reported a case with mucinous adenocarcinoma of the ileal neobladder 20 years after radical cystectomy for pT2 bladder cancer. Malignant transformation has also been reported in ileal conduit diversion, highlighting the rare but potential secondary malignant change, as well as the importance of long-term follow-up for patients undergoing ileal diversion after radical cystectomy.

This case illustrates a rare and delayed occurrence of intestinal-type adenocarcinoma in an ileal neobladder. It underscores the importance of maintaining long-term surveillance in patients with urinary diversions and considering neoplastic transformation in the differential diagnosis of unexplained hematuria or recurrent UTIs.