Interobserver variability in breast carcinoma grading results in prognostic stage differences.
Kimmie Rabe1, Olivia L Snir2, Veerle Bossuyt3
1Department of Pathology, Yale University School of Medicine New Haven, New Haven, CT.
Human Pathology
|October 27, 2019
Summary
Pathologist agreement on invasive breast carcinoma grading is good to very good. Discordant grading rarely impacts the final pathologic prognostic stage, ensuring reliable cancer staging.
Area of Science:
- Oncology
- Pathology
- Cancer Staging
Background:
- The AJCC Cancer Staging Manual 8th edition incorporated tumor grade into the pathologic prognostic stage for breast carcinomas.
- Tumor grading is known for its subjectivity, necessitating an evaluation of interobserver agreement.
Purpose of the Study:
- To assess interobserver agreement among pathologists for invasive breast carcinoma grading.
- To determine the impact of grading variability on the pathologic prognostic stage.
Main Methods:
- Six breast pathologists independently graded 100 invasive stage II breast carcinoma cases twice, with a 4-week washout period.
- Nottingham grading criteria were used, and inter- and intra-observer variability was assessed for overall grade and its components.
- Kappa statistics were employed to quantify agreement.
Main Results:
- Interobserver agreement was good to very good (κ range: 0.582-0.850), with higher intra-observer agreement (mean κ: 0.766).
- Tubule score demonstrated the highest reproducibility (κ=0.588).
- Complete concordance was achieved in 54 and 58 cases across two rounds; discordant grades led to different prognostic stages in only 25 cases, primarily shifting between stage IA and IB.
Conclusions:
- Pathologist agreement on invasive breast carcinoma grading is robust.
- Variations in grading have a minimal effect on the final pathologic prognostic stage, supporting its clinical utility.
