Liang H, et al. - A total of 158 specimens from 158 individuals with primary non-muscle invasive bladder cancer (NMIBC) were retrospectively analyzed by two independent pathologists in order to evaluate the presence of muscularis mucosae (MM) and stratify the T1 substage. Multivariable logistic regression analysis exhibited that the KTP laser resection method was related to the presence of MM in the specimen. Moreover, tumors with smaller sizes, which could also be en bloc resected with TURBt (such as ≤ 1 cm), had a greater presence of MM. Thus, en bloc resection enhances the recognition rate of MM, which may improve the precise determination of the T1 substage.