To count and how to count, that is the question: interobserver and intraobserver variability among pathologists in...

Area of Science:

• Surgical Pathology
• Oncology
• Cancer Staging

Background:

• Accurate cancer staging relies on determining the minimal number of lymph nodes retrieved.
• Variability in lymph node counting among pathologists has not been previously investigated.
• Standardized lymph node assessment is crucial for consistent cancer staging.

Purpose of the Study:

• To investigate inter-pathologist variability in lymph node counting on surgical slides.
• To identify factors contributing to disagreement in lymph node enumeration.
• To assess the clinical significance of variability in minimal nodal counts.

Main Methods:

• Ten pathologists independently counted lymph nodes on 15 distinct slides on two separate occasions.
• Pathologists also determined if specific structures qualified as countable lymph nodes.
• Discrepancies were analyzed concerning node quantity, size, proximity, and gross versus microscopic findings.

Main Results:

• Complete agreement among all pathologists on all slides and occasions was not achieved.
• The highest variability occurred on slides with more than 8 lymph nodes.
• Disagreements stemmed from criteria regarding node size, counting closely associated structures, and gross-microscopic discrepancies.

Conclusions:

• Significant inter-pathologist variability exists in lymph node counting, impacting cancer staging accuracy.
• The observed variability, with a 95% confidence interval of +/- 2.6 nodes around a mean of 5.7, can be clinically significant.
• Development and implementation of uniform criteria for lymph node counting are imperative for reliable cancer staging and comparative research.