Urothelial Carcinoma of Renal Pelvis
High-grade papillary urothelial carcinoma invading renal parenchyma (pathologic stage pT3). There is extensive involvement of the kidney with tumor cells infiltrating in between glomeruli and renal tubules. Such cases may sometimes mimic primary renal parenchymal tumor (such as collecting duct carcinoma). The presence of carcinoma-in-situ or a papillary component in the pelvicalyceal system would favor urothelial carcinoma. Nested or solid architecture and the presence of squamous metaplasia would also favor urothelial carcinoma over collecting duct carcinoma.