Aberrant TTF-1 expression in papillary high-grade urothelial neoplasm: case report and literature review

We herein report the case of a 48-year-old man who developed synchronous advanced tumors in the lung and the bladder. The most striking feature of our case is that the otherwise typical bladder urothelial carcinoma showed focal areas (comprising less than 5% of the tumor mass) of nuclear positivity for TTF-1 (thyroid transcription factor-1). The different pattern of cytokeratin expression led us to consider them two independent primary tumors. Several recent reports have indicated that the type of clone used can influence the results of TTF-1 staining and can explain positivity in extrapulmonary and extrathyroid tumors.