27 Pathological classification of urothelial neoplasms: practical choices for patient care

Abstract

Introduction: Morphological classifications systems that stratify neoplasms according to biological potential must define categories that are reproducible among practitioners, otherwise they create the heterogeneous population that they wish to avoid. This is particularly important for the classification of bladder neoplasms where follow‐up protocols are based on the risk of recurrence and progression. This risk is assessed according to their morphological classification.Materials and Methods: Previously forty‐nine cases of superficial bladder cancer (G1‐3pTa) representing an initial diagnosis of transitional cell carcinoma made in 1990 were identified and re‐graded using the 1998 WHO/ISUP classification by two pathologists. Inter‐observer agreement was assessed using Cohen weighted K statistics. After re‐classification the clinical follow‐up was reviewed retrospectively, and episodes of recurrence and progression noted. This paper compares those results to the same group of patients classified using the 1973 WHO scheme and followed up in a similar manner to try to determine if one system show better patient benefit over the other.Results: The interobserver agreement of pathologists using the 1998 WHO/ISUP scheme is moderate overall, but there is high disagreement when pathologists are asked to differentiate papillary urothelial neoplasms of low malignant potential from low grade carcinoma. The progression rates were very low for PUNLMPs and low grade carcinoma, but moderate for high grade carcinoma.Conclusions: The 1998 WHO/ISUP classification of urothelial neoplasms requires certain discriminations that cannot be reliably made by practitioners. Modifying the scheme to create categories of low grade neoplasm and high grade neoplasm would markedly increase its practical value to patients without significantly altering patient care.