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Open Access Research article

HER2 testing on core needle biopsy specimens from primary breast cancers: interobserver reproducibility and concordance with surgically resected specimens

Hitoshi Tsuda14*, Masafumi Kurosumi2, Shinobu Umemura3, Sohei Yamamoto4, Takayuki Kobayashi4 and Robert Yoshiyuki Osamura3

Author Affiliations

1 Diagnostic Pathology Section, Clinical Laboratory Division, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan

2 Department of Pathology, Saitama Cancer Center Hospital, 818 Komuro, Ina-machi, Kitaadachi-gun, Saitama 362-0806, Japan

3 Department of Pathology, Tokai University School of Medicine, Shimokasuya 143, Isehara, Kanagawa 259-1193, Japan

4 Department of Basic Pathology, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan

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BMC Cancer 2010, 10:534  doi:10.1186/1471-2407-10-534

Published: 7 October 2010

Abstract

Background

Accurate evaluation of human epidermal growth factor receptor type-2 (HER2) status based on core needle biopsy (CNB) specimens is mandatory for identification of patients with primary breast cancer who will benefit from primary systemic therapy with trastuzumab. The aim of the present study was to validate the application of HER2 testing with CNB specimens from primary breast cancers in terms of interobserver reproducibility and comparison with surgically resected specimens.

Methods

A total of 100 pairs of archival formalin-fixed paraffin-embedded CNB and surgically resected specimens of invasive breast carcinomas were cut into sections. All 100 paired sections were subjected to HER2 testing by immunohistochemistry (IHC) and 27 paired sections were subjected to that by fluorescence in situ hybridization (FISH), the results being evaluated by three and two observers, respectively. Interobserver agreement levels in terms of judgment and the concordance of consensus scores between CNB samples and the corresponding surgically resected specimens were estimated as the percentage agreement and κ statistic.

Results

In CNB specimens, the percentage interobserver agreement of HER2 scoring by IHC was 76% (κ = 0.71) for 3 × 3 categories (0-1+ versus 2+ versus 3+) and 90% (κ = 0.80) for 2 × 2 categories (0-2+ versus 3+). These levels were close to the corresponding ones for the surgically resected specimens: 80% (κ = 0.77) for 3 × 3 categories and 92% (κ = 0.88) for 2 × 2 categories. Concordance of consensus for HER2 scores determined by IHC between CNB and the corresponding surgical specimens was 87% (κ = 0.77) for 3 × 3 categories, and 94% (κ = 0.83) for 2 × 2 categories. Among the 13 tumors showing discordance in the mean IHC scores between the CNB and surgical specimens, the results of consensus for FISH results were concordant in 11. The rate of successful FISH analysis and the FISH positivity rate in cases with a HER2 IHC score of 2+ differed among specimens processed at different institutions.

Conclusion

It is mandatory to study HER2 on breast cancers, and either CNB or surgical specimen can be used.