Diagnosis: Urothelial carcinoma.

Comment: Favoring the diagnosis of urothelial carcinoma is the marked pleomorphism, presence of mitoses, tendency of growth in nests, and a prominent squamous differentiation. As for immunohistochemistry, PSA can be used as the first screening marker for differentiating high-grade prostate adenocarcinoma from high-grade urothelial carcinoma (Chuang AY et al. Immunohistochemical differentiation of high-grade prostate carcinoma from urothelial carcinoma. Am J Surg Pathol 2007;31:1246-55).