[Unusual variety of bladder urothelial carcinoma: "nest type" microlobular carcinoma: report of an anatomoclinical case and review of the literature].

We report a case of nested cell carcinoma, an uncommon transitional tumor. These tumors are composed of regular cuboidal transitional cells forming small nests with minimal cytologic atypia. Despite the benign course, this tumor resembling proliferation of Brunn's nests or inverted papilloma, must be considered as an aggressive transitional tumor. Thus, morphologic criteria are needed to make the diagnosis. Because of its aggressive behaviour, the surgical therapy depends on the tumor's infiltration.