Impact of the Micropapillary Variant in Urothelial Carcinoma of the Bladder—A Comprehensive Review of Meta-Analyses and Contemporary Cohort Studies

<b>Background/Objectives</b>: Micropapillary urothelial carcinoma of the urinary bladder (MPUC) represents a rare but highly aggressive histological variant of urothelial carcinoma (UC), frequently presenting at an advanced stage of disease. Although data on histological variants consistently suggest inferior oncological outcomes, the independent prognostic role of the micropapillary variant remains controversial. <b>Methods</b>: The present work synthesizes the findings of a large meta-analysis evaluating histological variants of UC and a separate meta-analysis focusing exclusively on MPUC, and further examines the most recent cohort-based evidence published between 2016 and 2025. <b>Results</b>: The presence of any histological variant in UC treated with radical cystectomy is associated with significantly worse recurrence-free survival, disease-specific survival, and overall survival, as reflected by pooled hazard ratios (HRs). For the micropapillary variant specifically, a modest increase in overall mortality has been demonstrated (pooled HR ≈ 1.20); however, results from adjusted analyses dedicated to MPUC remain inconsistent. <b>Conclusions</b>: Micropapillary urothelial carcinoma is consistently associated with adverse pathological features and poorer oncological outcomes. However, whether micropapillary morphology independently predicts prognosis beyond established factors such as pathological stage and nodal status remains uncertain, as adjusted analyses across studies have yielded inconsistent results. Part of the observed survival disadvantage may be explained by stage migration, although an intrinsic residual risk cannot be definitively ruled out. This review integrates contemporary population-based registry analyses with prior meta-analytic evidence to provide a clinically oriented synthesis of the prognostic and therapeutic implications of MPUC. In addition, we propose minimal reporting standards aimed at improving comparability across future studies and strengthening risk stratification and treatment decision-making.