Do amount of variant differentiation and mitotic rate in bladder cancer change with neoadjuvant chemotherapy?

Summary Neoadjuvant chemotherapy (NAC) is currently recommended to all candidate patients with muscularis propria-invasive bladder cancer. However, NAC is effective in only a subset of patients, and predictors of response are lacking. Our study aimed to characterize tumoral changes with NAC usage and to identify features at bladder biopsy/transurethral resection (Bx/TUR) that may predict response. A retrospective search was performed to identify patients with bladder cancer that were pT2 at Bx/TUR upon whom a radical cystectomy (RC) was performed from 2007 to 2010. A blinded slide review of the Bx/TUR and RC was conducted. Presence, type, percent of tumor variant morphology, and tumoral mitotic rate were assessed. Ninety RC patients with slides available were identified (46 NAC, 44 non-NAC). In NAC-treated patients, there was a significantly higher percentage of nonurothelial variant differentiation in the RC compared with Bx/TUR, whereas there was no difference in the non-NAC subgroup. Percent variant differentiation at Bx/TUR was not a predictor of response. There was a significant decrease in mitotic rate between Bx/TUR and RC in NAC patients, whereas there was no difference in the non-NAC subgroup, although mitotic rate was not a predictor of response. In conclusion, percent variant differentiation and mitotic rate changed significantly from Bx/TUR to RC with NAC usage, although neither predicted response. Pathologists should be aware that variant differentiation is common in bladder cancer, with increased presence after NAC, in order to improve recognition and documentation of these findings.