Prognostic factors in T1 bladder urothelial carcinoma: the value of recording millimetric depth of invasion, diameter of invasive carcinoma, and muscularis mucosa invasion

Summary pT1 bladder urothelial carcinomas represent a heterogeneous group of tumors with different biologic behaviors, and identifying the subset of tumors that carries a high risk of disease recurrence and progression is therefore important. We evaluated the prognostic significance of substaging 86 cases of pT1 bladder urothelial carcinoma based on different pathologic parameters. The mean tumor depth was 1.1 mm, and the mean diameter of the invasive focus was 2.2 mm. The mean number of tissue fragments with invasion was 4.4. Lymphovascular invasion and concomitant carcinoma in situ were present in 13% and 45% of cases, respectively. Although 56% of patients recurred, 18% experienced disease progression. Multivariate analysis showed a significant association between muscularis mucosa invasion ( P = .007), depth of invasion ( P = .0001), diameter of invasive focus ( P = .014), and progression. Furthermore, depth of invasion more than 3 mm was significantly associated with progression of disease, achieving a sensitivity of 31%, specificity of 99%, and predictive value of 79%. In comparison, the cutoff values for the diameter of invasive carcinoma that correlated best with outcome was 6 mm for progression. Lastly, combining both variables showed a strong prognostic accuracy where it predicted 94% of recurrences. Importantly, all cases with depth of invasion more than 3 mm and diameter more than 6 mm progressed. Lymphovascular invasion or concomitant carcinoma in situ did not correlate with outcome. From the current data, we do recommend reporting muscularis mucosa invasion whenever possible. Alternatively, tumor depth and tumor diameter should be included in the final pathology report in individual cases in which muscularis mucosa invasion cannot be assessed.