The nested variant of urothelial carcinoma: clinicopathology of 2 cases.

The nested variant of urothelial carcinoma is a recently described bladder tumor entity with a rare incidence. Two cases of this disease are presented in this report; the patients in both cases were elderly men, with a predominant involvement of the trigone region. Histologically, the tumor cells were arranged in ill-defined nests and had low-grade nuclear features. Both cases had a diffusely infiltrating growth pattern with widespread local disease at cystectomy. Strong immunohistochemical staining for p63 in the neoplastic cells supports the urothelial cell nature of this neoplasm. High p53 and Ki-67 indices of this tumor correlate with the aggressiveness of this subtype.