Interobserver agreement among pathologists for semiquantitative hormone receptor scoring in breast carcinoma

The American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines recommend reporting of hormone receptor test results in a semiquantitative manner. This study used 74 resected estrogen receptor (ER)-positive invasive breast cancers to determine reproducibility of semiquantitative scoring of hormone receptors using the H-score method. Four pathologists independently scored each slide. Agreement among observers was analyzed via Fleiss κ statistics on ER and progesterone receptor (PR) categorical scores. Intraclass correlation coefficient (ICC) was used to estimate the interobserver agreement for ER and PR H-scores on a continuous scale (0-300). There was 100% agreement for categorical ER results (κ = 1) and 97% agreement (κ = 0.823, P < .001) for categorical PR results. For quantitative H-scores, ICC agreement was 0.85 (95% confidence interval [CI] = 0.79-0.90) for ER and 0.87 (95% CI = 0.82-0.92) for PR. Because the H-score provides a continuous measure of tumor hormone receptor content, we suggest universal adoption of this method.