Von Brunn’s Nests in the Ureter of Two Cats

The aim of this work is to emphasize the importance of a differential diagnosis of von Brunn’s nests in cats from other urothelial neoplastic disorders, as transitional cell carcinoma, for a subsequent optimal care. Von Brunn’s nests and cysts are submucosal benign urothelial processes, related to irritative stimuli (calculi and urinary infections), characterized by an invagination with buds and clusters of normal urothelium in the lamina propria. They are common findings in the urinary bladder of human beings, but few cases have been described in dogs and cats. We report macroscopic, histopathological and, in one case, immunohistochemical features of these rare forms in the left ureters of two cats. Macroscopic evidence during surgery of ureteral nodules in two cats was accompanied by histopathological diagnosis and, in one case, by immunohistochemical assessment. Histopathology was coherent with a rare condition characterized by nests and islands of normal urothelium in the lamina propria and submucosa, with formation of cysts and moderate focal subacute inflammation. In one case epithelial cells of the nests showed well differentiated urothelial cells with an intense immunoreactivity to pan-cytokeratin (CK AE1/AE3), CK19 in the first outer layers, a slight immunoreactivity to CK20 and a low proliferative activity using MIB-1 (Ki67).