[Urothelial tumors and preneoplasias. Diagnostic problems and their clinical consequences]

The surgical pathology of biopsies or electroresection specimens taken from clinically suspicious or overt tumors in the urinary bladder encompasses the evaluation of a few parameters. This should allow the segregation of bladder tumor patients into subgroups with distinct clinical features and biological behavior, thus providing a rationale for choosing the best available therapy. In essence, the pathologist's role entails a careful morphologic assessment of the primary tumor, including evaluation of the histologic type, the growth pattern, the tumor grade, the tumor stage, and finally the presence and type of primary or tumor-associated flat intraurothelial lesions. Whereas the growth pattern of a lesion can be readily recognized, the correct grading and staging of papillary tumors are often more dependent on the complexity of the individual case and the experience of the pathologist due to the inherent subjectivity of the field and a lack of standardized criteria. These problems of intra- and interobserver variability are intimately coupled with the characteristics of the material, that is, bad orientation and tangential sectioning, thermal injury, crush and fixation artifacts, and limitations of the size of the samples. The correct evaluation and interpretation of flat intrauorothelial lesions suffer from similar difficulties and are further complicated by a confusing categorization and terminology. Although new modalities and molecular approaches have been introduced in recent years in an effort to overcome some of these obstacles, morphology still remains the most effective means to assess the biological behavior and prognosis of urothelial bladder cancer. The present article therefore addresses some of the diagnostically and clinically most relevant controversies and aims to give some useful hints for the evaluation of the above-mentioned morphological parameters. In addition, it adds some remarks on the morphological basis and diagnostic validity of urinary cytology in primary diagnosis and, more importantly, monitoring of bladder cancer patients.