En bloc resection improves the identification of muscularis mucosae in non-muscle invasive bladder cancer

Purpose: The T1 substage, according to the relationship between muscularis mucosae (MM) and tumors, is a promising prognostic factor for T1 bladder cancer. However, the identification rate of MM is low in specimens, and it is, therefore, not widely used in clinical practice. In this study, we investigated whether en bloc resection of non-muscle invasive bladder cancer (NMIBC) could improve the identification of muscularis mucosae (MM), which may further accurate identification of the T1 substage. Patients and methods: Specimens from 158 patients with primary NMIBC were retrospectively reviewed by two independent pathologists to assess the presence of MM and stratify the T1 substage. Of 158 specimens, 70 specimens were obtained via TURBt with a plasma kinetic loop and 88 were obtained via front-firing potassium-titanyl-phosphate (KTP) green-light laser en bloc resection. Univariable and multivariable logistic regression models were used to analyze the relationship between the clinical characteristics and the presence of MM. Results: The mean age was 58.22 years (range 18–85 years). Multivariable logistic regression analysis showed that the KTP laser resection method was associated with the presence of MM in specimens (P = 0.008). In addition, tumors with smaller sizes, which could also be en bloc resected with TURBt (e.g., ≤1 cm), had a higher presence of MM (P = 0.047). Conclusions: En bloc resection improves the identification rate of MM, which may enhance the accurate identification of the T1 substage.