Emerging concepts in micropapillary urothelial carcinoma

Micropapillary urothelial carcinoma is a relatively uncommon variant of urothelial carcinoma, but its recognition carries important prognostic and treatment implications. Micropapillary morphology occurs in neoplasms arising in many different organ systems and displays aggressive biologic behavior regardless of its site of origin. On account of this association, micropapillary features in urothelial carcinoma should be reported regardless of whether the pattern is focal or dominant. The overall prognosis for micropapillary urothelial carcinoma is poor and recent studies suggest that early treatment with cystectomy could improve outcome, as these tumors are unlikely to respond to chemotherapy when used as a secondary treatment modality. This review discusses the histologic features required for diagnosis and the clinical significance of rendering a diagnosis of micropapillary urothelial carcinoma.