Fig. 2

Histologic appearances of nephrogenic adenoma. a The tumor proliferated in very thin villous pattern with delicate core vessels. b Hobnail structure of the tumor cells with high N/C ratio was identified. Various size of glands were seen. c Comparatively small glands and (d) large glands with cystic change. Both of them had colloid-like eosinophilic secretion in the lumens. e, f Microtubular structures were also observed. They were quite similar to poorly differentiated adenocarcinoma or signet-ring cell carcinoma in part. g Mucin could be identified with PAS/Alcian-blue double stain. h Vimentin was diffusely positive with immunohistochemical analysis. i, j PAX8 was diffusely positive in all histological structures of nephrogenic adenoma. k PAX2 was also positive. l Ki-67 postive cells were very few