Macroscopic and microscopic findings. a. The macroscopic findings of renal cystic tumor (arrows). b. low power loupe images of 3 parts (①; cystic cavity, ②; renal cortex, ③; renal medulla). c. H&E stain. Marked lymphoplasmacytic infiltrate and storiform fibrosis. d. Storiform fibrosis with Azan staining e. Immunohistochemical result. A significant amount of IgG4-positive plasma cells infiltrates in renal medulla. f. Collecting duct was compressed longitudinary in renal cortex (arows). g. Collecting duct was dilated in renal in renal medulla (arrows). h. Collecting duct became narrowed and obstructed in renal medulla (arrows).