[Nested variant Transitional Cell Carcinoma. Report of two cases and bibliographic review.]

Nested type transitional cell carcinoma of the bladder is a rare histological variant among bladder tumors. Although clinical presentation is similar to the other bladder tumors, its macroscopic appearance may be equivocally benign, with submucosal growing which is difficult to detect on cystoscopy, so that diagnosis may be delayed.

We present the characteristics of nested type transitional cell carcinoma and review the differential diagnosis for this entity with possible counterfeiters.

In this article, we report two cases of nested type transitional cell carcinoma that presents, in one of them, all three growing patterns.

Microscopically nested transitional cell carcinoma is characterized by a cell distribution forming nests and tubules. They generally present low cytologic atypia simulating a low grade urothelial carcinoma, or benign bladder lesions such as von Brunn nests or nefrogenic adenoma.