Reproducibility and reliability of tumor grading in urological neoplasms

Histopathologic tumor grading reflects the degree of differentiation of a given tumor and for most urological tumors grading is an important factor in predicting their biological aggressiveness. Consequently, the clinical management of tumor patients is often strongly influenced by the tumor grade, provided by pathologists. This implicates that an ideal grading system should not only be of high prognostic relevance, but also of high reproducibility among different pathologists. To this end individual histological grading systems have been developed for different tumor entities and even for a given tumor type several grading systems have been proposed. All of these grading systems possess an inherent degree of subjectivity and consequently, both intra- and interobserver variability exist. In this review, grading systems for the most frequent urological tumors (i.e. prostate cancer, renal cell carcinoma, and urothelial tumors) are mentioned and data on the reproducibility and reliability of the most commonly used grading systems are summarized.