The Natural History, Treatment Pattern, and Outcomes of Patients With Micropapillary Bladder Carcinoma

Clinicopathologic Analysis of Micropapillary Urothelial Carcinoma of the Upper Urinary Tract: Implications for HER2-Targeted Therapy

Introduction/Background To determine the clinical significance of micropapillary urothelial carcinoma (MPUC) of the upper urinary tract (UTUC) and a potential therapeutic strategy. Patients and Methods A retrospective cohort study was conducted to examine the incidence of micropapillary UTUC from 2010 to 2018 and its clinicopathological characteristics. Clinical outcomes and cancer-specific survival (CSS) were compared between MPUC and conventional UTUC matched by stage within a 6-month variation of receiving surgery. Results A total of 24 MPUC cases were identified out of 901 cases (2.7%) of urothelial carcinoma (UC) of the renal pelvis and ureter. MPUC was significantly smaller (<3 cm) and associated with nodal metastasis compared with conventional UTUC (P = .017 & 0.021, respectively); however, no significant difference was observed for lymphovascular invasion, distant metastasis, or CSS (P > 0.50, respectively) compared with match controls. Six MPUC patients (25%) developed metastasis to the liver, lymph nodes, and lung during follow-up. Patients with HER2-positive MPUC (3 of 4) had a significantly higher risk of metastasis compared with HER2-negative MPUC (3 of 20; P = 0.035). Conclusions MPUC is an aggressive variant of UTUC and usually presents as a small locally advanced disease. HER2 immunohistochemistry may identify the subset of patients with micropapillary UTUC that are candidates for targeted therapy.

Cell Polarity Reversal Distinguishes True Micropapillary Growth From Retraction Artifact in Invasive Urothelial Carcinoma

Focal micropapillary features in invasive urothelial carcinoma is sometimes difficult to distinguish from retraction artifact morphologically. Cell polarity reversal has been demonstrated in micropapillary tumors by epithelial membrane antigen (EMA) immunostaining. We have previously described the use of E-cadherin as a cell polarity marker in ovarian micropapillary serous borderline tumors. The aim of this study was to evaluate the utility of immunohistochemistry for EMA and E-cadherin in differentiating micropapillary urothelial carcinoma from retraction artifact. We identified 29 invasive urothelial carcinomas with micropapillary features and 30 invasive urothelial carcinomas without reported micropapillary features but with areas of retraction artifact. Cell polarity reversal was considered present if E-cadherin showed membranous apical cup-like staining or if EMA demonstrated a well-defined basal staining towards the stroma. Twenty-seven of 29 cases (93%) of urothelial carcinoma with micropapillary features demonstrated EMA or E-cadherin staining patterns consistent with cell polarity reversal. Staining consistent with micropapillary architecture was identified with both markers in 20 of these 27 cases (74%). Six cases showed reversal of polarity by E-cadherin alone, whereas 1 case showed polarity reversal by EMA alone. Retraction artifacts showed circumferential staining by E-cadherin and lacked well-defined basal staining by EMA. Three cases originally classified as with retraction artifact showed reversal of cell polarity by both EMA and E-cadherin and were reclassified as micropapillary. Our data show that pathologists can reliably make this distinction in most cases. However, in some cases with ambiguous features, EMA and E-cadherin immunostaining may aid in resolving this diagnostic dilemma.

Micropapillary Bladder Cancer: Insights from the National Cancer Database

Introduction: Micropapillary bladder cancer (MPBC) is a variant histology of urothelial carcinoma (UC) that is associated with poor outcomes however given its rarity, little is known outside of institutional reports. We sought to use a population-level cancer database to assess survival outcomes in patients treated with surgery, radiation therapy and/or chemotherapy.

Materials and Methods: The National Cancer Database (NCDB) was queried for all cases of MPBC and UC using International Classification of Disease-O-3 morphologic codes between 2004–2014. Primary outcome was survival outcomes stratified by treatment modality. Treatments included radical cystectomy (RC) with or without neoadjuvant chemotherapy (NAC) or adjuvant chemotherapy (AC).

Results: Overall 869 patients with MPBC and 389,603 patients with UC met the inclusion criteria. Median age of the MPBC cohort was 69.9 years (58.9–80.9) with the majority of the cohort presenting with high-grade (89.3%) and muscle invasive or locally advanced disease (47.6%). For cT1 MPBC, outcomes of RC and BPS were not statistically different. For≥cT2 disease, NAC showed a survival benefit compared with RC alone for UC but not for MPBC. On multivariable analysis, MPBC histology independently predicted worse increased risk of death. On subanalysis of the MPBC RC patients, NAC did not improve survival outcomes compared with RC alone.

Conclusions: Neoadjuvant chemotherapy utilization and early cystectomy did not show a survival benefit in patients with MPBC. This histology independently predicts decreased survival and prognosis is poor regardless of treatment modality. Further research should focus on developing better treatment options for this rare disease.