First reported case of peri-ureteric urothelial carcinoma.

We report the first documented case of peri-ureteric, low-grade urothelial carcinoma presenting over two decades after initial non-muscle-invasive bladder cancer (NMIBC). A 75-year-old male, treated with intravesical BCG, remained recurrence-free for ten years before developing a low-grade bladder recurrence after ten years. Surveillance imaging revealed left hydronephrosis and peri-ureteric thickening despite normal ureteroscopy and negative cytology. CT-guided biopsy confirmed low-grade papillary urothelial carcinoma external to the ureter. Robot-assisted nephroureterectomy showed a non-invasive tumour encasing, but not invading, the ureter, suggesting origin from ectopic urothelial nests. This rare presentation highlights a surveillance blind spot for extraluminal urothelial carcinoma.