A variant of transitional cell carcinoma: the << nested variant of urothelial carcinoma >> report of two cases

We report two cases of a poorly known variant of transitional cell carcinom a, the "nested variant of urothelial carcinoma". This tumor is composed of small islands or nests of transitional cells, presenting little atypia and mimicking von Brunn's nests. This low grade tumoral variant seems to behave as a high grade tumor of the same stage. Deep biopsies are necessary to di splay tumoral invasion, which allows the diagnosis. Importance of the knowl edge of this entity is highlighted in order to avoid misdiagnoses that coul d delay appropriate therapy.