Invasiveness or growth pattern in urothelial tumours. A perspective to rethink the current WHO classification.

According to the current WHO classification, urothelial tumors consist of non-invasive urothelial neoplasms and invasive urothelial carcinoma which is supposed to include all tumors with invasion regardless of extent and pattern. Some pathologists are uncomfortable about such all-inclusive definition of invasive urothelial carcinoma and it is questionable whether invasiveness is a valid defining feature for primary distinction of urothelial tumors. Considering that most pathologists understand urothelial tumors based on the dual-track pathway model, we would like to raise concern that it may be necessary to rethink the validity of the current WHO classification compared to the restructuring into papillary vs non-papillary tumors. In our opinion, such restructuring would align the WHO classification with the pathogenesis model and could clarify the diagnostic terminology regarding invasiveness. The term of urothelial carcinoma in situ may also be reconsidered.