Urothelial carcinoma "nested variant" of renal pelvis and ureter.

The nested variant of urothelial carcinoma is a rare type of urothelial invasive carcinoma. It is characterized by islands of discrete to moderate atypical urothelial cells that strongly simulate von Brunn nests and invade to the lamina propria or deeper. Almost all described cases have been located in the bladder. We report a case of nested variant of urothelial carcinoma of the renal pelvis and ureter, synchronous with high-grade urothelial papillary carcinoma.