Prognostic Significance of Mitotic Activity in Noninvasive, Low-Grade, Papillary Urothelial Carcinoma.

Objective: To identify the most useful method to detect the mitotic count (MC) by comparing different techniques, to determine a cutoff value for mitotic activity (MA), and to evaluate the correlation of this value with the recurrence of noninvasive low-grade papillary urothelial neoplasm (LGPUC).

Study Design: Hematoxylin and eosin-stained slides of 55 LGPUC cases were evaluated for their MA. MC was determined using 4 different methods. In Method 1, cases with 3 mitoses in 1 single focus of a high-power field (HPF x 400) were found, and in Method 2, cases with ≥ 5 mitoses in 1 singlefocus of an HPF, in any level of the neoplastic epithelium, were determined. The areas with the highest MA values in the lower third and those with the highest MA values in the upper two-thirds of the neoplastic epithelium were marked in Methods 3 and 4, respectively. Then, mitotic figures were counted in these fields, and cases with 5 mitoses were determined.

Results: In the recurrent group the number of cases with ≥ 5 mitoses, as detected by Methods 2 and 4, was significantly higher than that found for the nonrecurrent group (p = 0.0001 and p = 0.002, respectively). The number of mitoses, as detected by Methods 1 and 3, was not significantly different between the groups.

Conclusion: We suggest that determining MC may be used as a prognostic marker to predict LGPUC recurrence and that the mitotic numbers should be included in the initial pathology report to guide the clinician in patient management.