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Updated: May 5, 2026
Building Up a High-throughput Screening Platform to Assess the Heterogeneity of HER2 Gene Amplification in Breast Cancers
Published on: December 5, 2017
Comparative Analysis of Equivocal (2+) and Positive (3+) HER2 Immunohistochemistry (IHC) and Bright-Field Dual-Color
Kroonpong Iampenkhae1,2, Adiluck Pisutpunya3, Chawinthorn Vuthithammee1,2
1Department of Pathology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Background:
Human epidermal growth factor receptor 2 (HER2) is an important predictive and prognostic biomarker in breast cancer. Immunohistochemistry (IHC) is the preferred initial test due to its cost-effectiveness and simplicity. While fluorescence in situ hybridization (FISH) is the traditional gold standard test for HER2 gene amplification, DISH has emerged as an accepted alternative that allows evaluation under a standard light microscope.
Objectives:
To evaluate agreement between HER2 IHC (2+/3+) and DISH in node-positive primary breast cancers and compare findings with published IHC and FISH data.
Design:
Retrospective single-center cohort study using nationwide referral specimens.
Methods:
Cases of pathologically confirmed lymph node metastasized invasive breast carcinoma with HER2 IHC scores of 2+ and 3+ were retrieved. Interpretation of HER2 IHC was performed using the 2023 ASCO/CAP guideline. HER2 DISH was conducted and evaluated by the HER2/CEP17 signal ratio on primary tumors first, and on metastasized lymph nodes in cases of persistent technical failure.
Results:
Among 1,307 breast cancers, DISH detected HER2 amplification in 933 cases, including 92% (760) of IHC 3+ cases and 36% (173) of IHC 2+ cases. Seven cases with persistent technical failure on primary tumors were resolved when switching to lymph node specimens. Comparison with the meta-analysis data of IHC and FISH showed no significant differences, indicating that DISH is a reliable alternative to FISH.
Conclusion:
Our study demonstrates a high concordant rate between HER2 IHC and DISH in the IHC 3+ group and a low positive rate in the IHC 2+ group. We found no significant difference in the positive rates of HER2 IHC to DISH when compared with prior data of IHC to FISH, reaffirming the use of HER2 DISH as an effective and more accessible alternative to FISH in HER2 2+/3+ breast cancer.
