Non-Invasive Papillary Urothelial Carcinoma with "Micropapillary" Architecture: Clinicopathologic Study of 18 Patients Emphasizing Clinical Outcomes

• Published in: Histopathology
• Main Authors: Sangoi, Ankur R, Cox, Roni M, Higgins, John P, Quick, Charles M, McKenney, Jesse K
• Format: Journal Article
• Language: English
• Published: England 22.05.2020
• Subjects: non-invasive; carcinoma; micropapillary; bladder; urothelial
• ISSN: 1365-2559

Invasive micropapillary carcinoma is a recognized aggressive urothelial carcinoma variant. One prior study focusing on non-invasive (pTa) high grade papillary urothelial carcinoma with micropapillary architecture has been reported. We collected bladder transurethral resection specimens showing non-invasive high grade papillary urothelial carcinoma with non-hierarchical secondary papillae lacking fibrovascular cores (i.e. micropapillary architecture). Cases with any invasive component or any prior history of invasive urothelial carcinoma were excluded. 20 cases were identified from 16 male and 2 female patients (ages 55-86 years). Micropapillary architecture comprised from 10%-95% (mean 31%), but non-invasive cribriform [15 cases (comprising 5-60%, mean 19%) and villoglandular patterns [9 cases (comprising 5-60%, mean 24%) were commonly admixed. Treatment data were available for 16 patients: surveillance (n=13), cystoprostatectomy (n=1), BCG plus mitomycin (n=1), and BCG (n=1). Follow-up data was available from 16 patients (range 1-128 months, mean 50 months): 13 patients had no new occurrences to date (81%), 2 had stage progression to pT1 papillary urothelial carcinoma (13%) with one dieing of other causes, and 1 died of other causes with no evidence of disease (6%). Non-invasive urothelial carcinomas with micropapillary architecture are often admixed with non-invasive cribriform and villoglandular patterns. Stage progression to lamina propria invasion in only 2 of 16 patients (13%) is not higher than expected for otherwise typical pTa high grade urothelial carcinomas and no progression to invasive micropapillary carcinoma was identified, adding further support to the current World Health Organization recommendation excluding use of the term "micropapillary" for pTa urothelial carcinoma.