Mimickers of urothelial neoplasia.

Management of malignant urothelial tumors is often associated with extended costly treatments, some with significant morbidity. Advanced tumors are treated with radical cystectomy with neoadjuvant or adjuvant radiation or chemotherapy. Over and under interpretation of histological findings from biopsies and transurethral resections of urothelial lesions may either incur treatments with significant side effects or miss a possible window of cure, respectively. Herein we reflect our approaches and common diagnostic challenges of urothelial tumors and their mimickers, and highlight the diagnostic pitfalls and key histological and immunohistochemical differentiating features. It is useful to separate mimickers of bladder adenocarcinoma and mimics of urothelial carcinoma as the former can involve the muscularis propria, whereas the latter do not. Glandular mimickers discussed herein include cystitis cystica et glandularis with intestinal (colonic) metaplasia, endocervicosis and endometriosis, and nephrogenic adenoma. Common mimickers of urothelial carcinoma include polypoid cystitis, pseudocarcinomatous urothelial neoplasia, inverted urothelial papilloma, florid proliferation of von Brunn nests, and reactive urothelial metaplasia associated with prostatic infarction. We emphasize where clinical impression and history are important for the correct diagnosis. In some entities assessment of the entire histological picture is critical rather than focusing on isolated findings that out of context may be indistinguishable from cancer.