Objective: to develop optimal techniques of en-bloc resection of large non-muscle invasive bladder tumors, determine the proper method of specimen extraction and assess the quality of specimens obtained by different techniques.
Materials and methods. A total of 12 patients with primary cT1 bladder cancer underwent transurethral en-bloc resection between January 2018 and March 2019 were enrolled into the study. Tumor size ranged from 3.5 cm to 6.2 cm. For removal and extraction of large bladder tumors using thulium fiber en-bloc laser three different techniques were developed: “swiss cheese technique”, “crown and root technique” and “three steps technique” technique». The main pathologic criteria used for assessment of removal technique were tumor grade (G), depth of invasion (T), presence of carcinoma in situ (CIS), variant histology (VH), lymphovascular invasion (LVI), presence of detrusor muscle. Additional criteria were horizontal and vertical resection margin, subclassification of T1-stage and presence of focal necrosis in tumor.
Results. Among the techniques developed and tested, the best quality of specimens for morphological evaluation was obtained using the combined «crown and root technique». First step is electroresection of the exophytic part of the tumor into pieces, and the next step is en-bloc laser resection (using thulium fiber or holmium laser) of the tumor base. Overall, the quality of all specimens obtained using three techniques met the current requirements of pathologic study.
Summary. En-bloc resection techniques of large bladder tumors allow obtaining specimen suitable for proper morphological evaluation and correct tumor staging. Further studies are required to evaluate the impact of these techniques on long-term results of treatment options.

Keywords: laser en-bloc resection, papillary urothelial carcinoma, non-muscular invasive bladder cancer, thulium fiber laser