Interobserver and Interantibody Reproducibility of HER2 Immunohistochemical Scoring in an Enriched HER2-Low–Expressing Breast Cancer Cohort.
- Resource Type
- Article
- Authors
- Karakas, Cansu; Tyburski, Haley; Turner, Bradley M; Wang, Xi; Schiffhauer, Linda M; Katerji, Hani; Hicks, David G; Zhang, Huina
- Source
- American Journal of Clinical Pathology. May2023, Vol. 159 Issue 5, p484-491. 8p.
- Subject
- *BREAST cancer
*IMMUNOGLOBULINS
*BREAST
*PATHOLOGISTS
- Language
- ISSN
- 0002-9173
Objectives We assessed the interobserver and interantibody reproducibility of HER2 immunohistochemical scoring in an enriched HER2-low–expressing breast cancer cohort. Methods A total of 114 breast cancer specimens were stained by HercepTest (Agilent Dako) and PATHWAY anti-HER2 (4B5) (Ventana) antibody assays and scored by 6 breast pathologists independently using current HER2 guidelines. Level of agreement was evaluated by Cohen κ analysis. Results Although the interobserver agreement rate for both antibodies achieved substantial agreement, the average rate of agreement for HercepTest was significantly higher than that for the 4B5 clone (74.3% vs 65.1%; P =.002). The overall interantibody agreement rate between the 2 antibodies was 57.8%. Complete interobserver concordance was achieved in 44.7% of cases by HercepTest and 45.6% of cases by 4B5. Absolute agreement rates increased from HER2 0-1+ cases (78.1% by HercepTest and 72.2% by 4B5; moderate agreement) to 2-3+ cases (91.9% by HercepTest and 86.3% by 4B5; almost perfect agreement). Conclusions Our results demonstrated notable interobserver and interantibody variation on evaluating HER2 immunohistochemistry, especially in cases with scores of 0-1+, although the performance was much more improved among breast-specialized pathologists with the awareness of HER2-low concept. More accurate and reproducible methods are needed for selecting patients who may benefit from the newly approved HER2-targeting agent on HER2-low breast cancers. [ABSTRACT FROM AUTHOR]