Patient history Past medical history is notable for hematuria, hypertension, non-insulin-dependent diabetes mellitus, Warthin tumor of the left parotid, pleomorphic adenoma of the right parotid, tubular adenoma, and adenomatous polyps colon, thyroid disorder, tonsillectomy, pilonidal cyst and arthritis. Hospital Course A 79-year-old male presented with macroscopic hematuria and palpable hydronephrosis of the right kidney. Ureteroscopy found blockage of the right ureter by a mass, and biopsy revealed features consistent with a high-grade papillary urothelial carcinoma. A radical nephroureterectomy was performed. General description The right kidney and portion of the ureter were surgically removed. Opening of the ureter revealed two distinct gray-tan papillary lesions. One was 4.0 cm long and had an open circumference of 2.0 cm, was located 4.0 cm from the ureteropelvic junction, and occluded the lumen. The other was 0.8 cm long and had an open circumference of 0.5 cm, did not occlude the lumen, and was located 2 cm from the ureteral margin. The remaining renal ureteral and pelvic mucosa was unremarkable. The kidney revealed markedly dilated renal pelvis and calyces. Diagnosis Microscopic examination of the larger occlusive lesion is consistent with a high-grade papillary urothelial carcinoma invading the muscularis propria (Fig. 1). Additional focus revealed a high-grade papillary urothelial carcinoma without invasion of the lamina propria or muscularis propria (Fig. 2). In random sampling of the ureter and walls of the renal pelvis, focal urothelial carcinoma in situ is also noted (Fig. 3). DiscussionUrothelial carcinomas most commonly occur in the urinary bladder but can occur at any site containing urothelium including the upper urinary tract from the ureteral orifice to the renal calyces. Upper urinary tract tumors represent 5-10% of all renal tumors and 5-7% of all urothelial tumors [1]. The types of urothelial tumors of the upper urinary tract mirror those that originate in the bladder. The four morphological growth patterns include papilloma-papillary, invasive papillary, non-invasive flat carcinoma, and invasive flat carcinoma [2]. Papillomas are benign, exophytic structures with finger-like papillae, central fibrovascular core with epithelium resembling typical urothelium. Inverted papillomas that are benign lesions, but extend into the lamina propria, may occur. Papillary urothelial neoplasms of low malignant potential (PUNLMP) show a thicker urothelium or diffuse nuclear enlargement with rare mitotic figures. Low-grade papillary urothelial carcinomas are cohesive and maintain polarity with some nuclear atypia and infrequent mitotic figures. High-grade papillary urothelial tumors present with discohesive cells with large hyperchromatic nuclei, frank anaplasia, and frequent mitotic figures.