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UROLOGICAL
ONCOLOGY
Interobserver
discrepancy using the 1998 World Health Organization/International Society
of Urologic Pathology classification of urothelial neoplasms: practical
choices for patient care
Murphy WM, Takezawa K, Maruniak NA
Department of Pathology, University of Florida College of Medicine, Gainesville,
Florida, USA
J Urol. 2002; 168: 968-72
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Purpose: Morphological
classifications designed by experts to stratify neoplasms according
to biological potential must define categories that are reproducible
among practitioners or the schemes actually create the heterogeneous
populations that they seek to avoid. The application of the 1998 World
Health Organization/International Society of Urologic Pathology scheme
for urothelial neoplasms was studied in a community practice setting.
We documented interpretive discrepancies for each category of neoplasm
and determined whether a period of pathologist education may have a
positive effect on the frequency of discrepant interpretations. The
results suggest that patients may benefit from modifying the classification
system.
- Materials
and Methods: A consecutive series of specimens was divided
into learning and study sets that were each independently examined by
3 pathologists. Specimens in the learning set were interpreted without
previous structured education, while those in the study set were interpreted
immediately after intensive education. Interpretations for each specimen
were compared and interpretive discrepancies were analyzed.
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Results: Case
distribution after education was similar among the pathologists but
interpretations for any particular specimen often differed. The level
of interpretive discrepancies varied according to the morphological
similarity among categories in the classification scheme and was not
necessarily decreased by education. When pathologists were required
to discriminate between papillary urothelial neoplasm of low malignant
potential and low grade carcinoma, the discrepancies were 50% after
education compared with 39% before education. In contrast, there were
no discrepancies when the discrimination was between papillary urothelial
neoplasm of low malignant potential and high grade carcinoma or carcinoma
in situ. Eliminating categories with poor reproducibility markedly improved
the likelihood of unanimous agreement among practitioners but a probably
irreducible level of 10% discrepancies remained.
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Conclusions: The
1998 World Health Organization/International Society of Urologic Pathology
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 carcinoma
would markedly increase its practical value to patients without significantly
altering patient care.
- Editorial
Comment
In 1998, the WHO/International Society of Urological Pathology decided
upon a new classification of urothelial neoplasms. Upon reviewing the
literature on this subject, I came upon this reference, which gives
some insight into the difficulties with classification systems of urothelial
neoplasms in general, and with the new classification in special.
After education of pathologists, general agreement on low malignant
potential papillary urothelial neoplasms was achieved in 39%, on low
grade carcinomas in 23%, whereas agreement was achieved on high grade
carcinomas and carcinoma in situ in 80% and 77%, respectively.
For the urologist this means that the information on dangerous carcinomas
is quite reliable whereas it is rather unreliable in more benign disease
– these however make more than 70% of our cases.
Dr.
Andreas Bohle
Professor of Urology
HELIOS Agnes Karll Hospital
Bad Schwartau, Germany |