As for many other tumors it is likely that depth of invasion is a major prognostic factor for disease recurrence and progression in high grade pT1 urothelial bladder cancer. To date nor pathological anatomy based neither dimensional subclassification proved reliable correlation with recurrence and progression, mainly considering the high interobserver variability in pT1 diagnosis, biased by the TURB resection technique intrinsic artifact (tangential sectioning, thermal crush, absence of muscularis mucosae in routine specimen). A novel procedure, En Bloc TURB, can both improve the sample evaluation, especially for what concern depth of tumor invasion and margins status, and allow accurate histological based risk stratification: the possibility to analyze perfectly oriented specimen, with easily recognizable lamina propria structure and no doubt in invasion assessment, is the only way to compare tumor, and validate or disprove the role of depth of invasion in bladder cancer. Comparison of measurements will eventually reveal statistical correlation between the depth of invasion measurement and other validated clinical parameters or assess a role as independent prognostic factor for the histological parameter.
The correlation of invasion depth with tumor aggressiveness has been widely experienced (i.e. melanoma Breslow measurement, Depth on invasion DOI in head and neck squamous cell carcinoma, submucosal invasion depth SID in colorectal carcinoma) and presumably the same approach is applicable to high-grade urothelial bladder carcinoma with results similar to that obtained for other malignancies. In this context the utility of en-bloc excisional specimen relies on the possibility of tumor orientation, with clear identification of surgical margin on gross examination. This would allow histological correlation between tumors using histologic landmark, since all anatomic structure are easily identifiable on H&E slices from oriented sample.In a pathological point of view En Bloc TURB can both improve the sample evaluation, especially for what concern depth of tumor invasion and margins status, and allow accurate histological based risk stratification. We are deeply confident that the introduction in common surgical practice of much representative tumor sample, obtained with tissue respectful techniques such as en-bloc TURB, could improve our outcome prediction tools: the possibility to analyze perfectly oriented specimen, with easily recognizable lamina propria structure and no doubt in invasion assessment trough reproducible measurement method, is the only way to compare tumor, and validate or disprove the role of neoplastic invasion thickness in mm. In line with other epithelial malignancies, staging according to depth of invasion hold the promise to improve our understanding in this heterogeneous group of neoplasm. Target of this prospective study is to get over problems affecting the TURB procedure in order to verify if tumoral thickness is actually an outcome predictive variable, and if so, to set a significant cutoff. The availability of histological sample faithfully reproducing all the anatomical relationship within lamina propria components, with clear invasion assessment and identification of structures involved, may eventually lead also to the introduction of an anatomy based sub-classification of tumor (i.e. according to muscularis mucosae spatial relationship).