Ureteric Bud-derivatives in Wilms Tumor and Nephrogenic Rest

Expression of the KRT17 protein in foetal kidneys, nephrogenic rests and Wilms’ tumors. The background was stained with Mayer’s haematoxylin. A) KRT17 (brown staining) expressed exclusively in utereric bud (UB). No positive immunreaction was seen in surrounding blastemal cells and S-shaped body (SSB). B) Strong KRT17 immunreaction in each cell of the medullary collecting duct (arrows). C) Tubular cells of a perilobar nephrogenic rests are negative for KRT17, but some UB-derived tubules display KRT17 positivity (arrows). Differentiated cortical collecting ducts also show a week KRT17 taining (short arrows). D) A hyperplastic perilobular nephrogenic rest negative for KRT17 staining but larger tubules with columnar epithels show positive KRT17 staining (arrows). E) A single UB-derivative tubulus lined by tall columnar cells display strong KRT17 staining (star). It is surrounded with tumorous blastemal cells resembling induction/aggregation phase around the UB in embryonal kidneys. F) Dilated UB-derived tubulus (star) surrounded by blastemal cells. G) Two UB-like tubules lined with KRT17 positive tall columnar cells (star) embedded in fibroblastic stroma. H) A group of epithelial tubules, two of them with KRT17 positive cells surrounded with stromal differentiated blastemal cells. I) Smaller and larger tubules, some resembling renal vesicles in epithelial predominant Wilms’ tumor. Lack of KRT17 staining indicates their blastemal origin. A-I the same magnification, Scale bar: 35 μm.