The Influence of Inverted Growth Pattern on Recurrence for Patients with Non-Invasive Low Grade Papillary Urothelial Carcinoma of Bladder

AIMS: To evaluate the impact of a histologically inverted pattern on recurrence in patients with newly diagnosed non-invasive, low-grade papillary urothelial carcinoma of the urinary bladder. METHODS: A total of 81 patients with primary bladder non-invasive, low-grade papillary urothelial carcinoma diagnosed in a single tertiary-care centre who had at least 1-year follow-up after an initial resection were included. All slides from each case were reviewed to determine the growth pattern (exophytic versus endophytic, i.e. inverted) and other histological parameters. Clinical data were retrieved from hospital records. RESULTS: Disease recurrence occurred in 41 (50.6%) patients. Cases with an inverted pattern showed a lower recurrence rate than those with pure exophytic tumours (37.5% versus 52.1%), a longer time to first recurrence (mean 34 versus 21.5 months) and fewer recurrence episodes (p=0.482, 0.564 and 0.051, respectively). All recurring inverted cases recurred only once during follow-up. No tumour with >80% inverted architecture recurred. CONCLUSION: Our results suggest that non-invasive, low-grade papillary urothelial carcinoma of the bladder tends to have a better outcome in terms of disease recurrence if it shows an inverted growth pattern. To indicate the presence and percentage of the inverted pattern in low-grade urothelial carcinomas in the pathology report might be considered as an adjunct to help long-term patient management.