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HER-2 status determination in breast carcinomas. A practical approach
T García-Caballero1, M D Menéndez, A Vázquez-Boquete
1Department of Morphological Sciences, Faculty of Medicine, University Clinical Hospital of Santiago de Compostela, Spain. cm-tgc@usc.es
Histology and Histopathology
|December 24, 2005
Summary
Accurate human epidermal growth factor receptor 2 (HER2) testing is vital for breast cancer treatment selection. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are key methods, with IHC being more accessible but requiring standardization for reliable HER2 status determination.
Area of Science:
- Oncology
- Pathology
- Molecular Diagnostics
Background:
- Accurate human epidermal growth factor receptor 2 (HER2) status evaluation is critical for selecting breast carcinoma patients eligible for trastuzumab therapy.
- Various laboratory methodologies exist for HER2 assessment, each with distinct advantages and limitations.
Purpose of the Study:
- To analyze and compare the results of routine immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) for determining HER2 status in breast invasive ductal carcinoma.
- To assess the concordance and utility of both IHC and FISH in clinical practice.
Main Methods:
- Five hundred and three cases of invasive ductal breast carcinoma were analyzed for HER2 overexpression using immunohistochemistry (HercepTest).
- Sixty equivocal HercepTest 2+ cases were further evaluated for HER2 gene amplification using fluorescence in situ hybridization (FISH).
Main Results:
- HER2 overexpression was detected in 19% (97/503) of cases by IHC.
- FISH analysis revealed HER2 gene amplification in 18% (11/60) of equivocal IHC cases.
- Combined IHC and FISH identified HER2 overexpression or gene amplification in 21% of the studied breast carcinomas.
Conclusions:
- Immunohistochemistry offers a standardized, accessible method for HER2 status determination in pathology labs, unlike FISH.
- Standardization of fixation, automation, and pathologist training are crucial for reliable IHC results.
- FISH is recommended for analyzing equivocal IHC results, preferably in reference laboratories, to ensure diagnostic accuracy.