The nested variant of transitional cell carcinoma--a rare neoplasm with poor prognosis.

The "nested" variant of transitional cell carcinoma is a rare variant composed of apparently clusters of urothelial cells, of benign appearance, which often simulate von Brunn's nests and invade into the lamina propria or deeper. Only 36 cases have been reported to date and herein we report an additional 10 cases. Of these 10 cases treated with locoregional therapy, seven died of disease or treatment complications 4-40 months after diagnosis while one patient died of unrelated disease after 90 months. Follow-up is < or = 1 year for the remaining two patients. Our data and a review of the literature supports the assertion that the nested variant of transitional cell carcinoma is an aggressive neoplasm.