Impact of the 1998 World Health Organization/International Society of Urological Pathology classification system for urothelial neoplasms of the kidney

Abstract

The classification of urothelial neoplasms of the kidney traditionally has been similar to that of urinary bladder tumors. Several years ago, the classification of papillary urothelial neoplasms was revised. The current study focuses on the application of the 1998 World Health Organization (WHO)/International Society of Urological Pathology classification system to 102 renal pelvic urothelial neoplasms and compares it to the 1973 WHO classification scheme. In this study, all tumors were classified as urothelial carcinomas, and the majority (85%) were papillary. Most patients with papillary tumors presented with 'superficial' disease (rpT1). With the 1998 system, most papillary carcinomas were high grade, and were more often invasive as compared to low-grade tumors. Only 34% were low-grade papillary tumors and, of these, most (93%) were noninvasive. With the 1973 system, most papillary tumors were grade 2 or 3, with invasion more common in grade 3 tumors. By 1973 criteria, grade 2 tumors were a heterogeneous group; with 1998 criteria, nearly one-half were high grade and the other half low grade. The grade of papillary urothelial carcinomas with both the 1973 and 1998 grading methods was associated with stage (P ¼ 0.001). Our study reveals that papillomas and papillary urothelial neoplasms of low malignant potential are uncommon tumors in the kidney. Renal pelvic papillary urothelial neoplasms are most often carcinomas and are more commonly high grade than low grade. Although both the 1973 and 1998 systems showed a significant association with tumor stage, grade 2 papillary carcinomas are a heterogeneous group by 1973 criteria. The 1998 system provides useful information in that it more clearly defines a papillary tumor's grade and selects for a group of tumors, namely low-grade papillary urothelial carcinomas, for which a low likelihood of invasion can be predicted.

A nuclear grading system is a strong predictor of survival in epitheloid diffuse malignant pleural mesothelioma

“…These findings are consistent with what has been observed in other malignancies 15,17,26,31,32 and confirms that our grading system correlates with the malignant potential of epithelioid diffuse malignant pleural mesothelioma.…”

pT classification, grade, and vascular invasion as prognostic indicators in urothelial carcinoma of the upper urinary tract

“…It was associated with high tumor stage and grade, and proved to be the strongest predictor of poor patient outcome. Comparable observations have been made by other groups detecting vascular invasion in 25-47% of cases with prognostic impact both in univariate 14,17,22,38 and multivariate 23,24,29 analyses. Owing to the large sample size, we were able to demonstrate that the prognostic impact of vascular invasion increases with increasing pT classification and grade, as has recently been reported for bladder cancer.…”

Non‐invasive papillary urothelial neoplasms: The 2004 WHO/ISUP classification system

“…In the 1973 WHO system, a large percentage of non‐invasive papillary urothelial carcinomas were called grade 2, an ambiguous group that the urologists were not sure how to manage. In the 2004 WHO/ISUP system, however, these grade 2 tumors can be segregated approximately equally into low‐ and high‐grade carcinomas with correspondingly low and high risks of progression 9–11 …”