HER2 testing in multifocal/multicentric breast cancer: should all foci be tested in the context of HER2-low and HER2-ultralow?
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View abstract on PubMed
Summary
This summary is machine-generated.Multifocal and multicentric breast cancer (MMBC) shows significant HER2 expression heterogeneity. Testing all tumor foci is crucial for accurate HER2 status and optimal treatment selection, especially for HER2-low and HER2-ultralow cases.
Area Of Science
- Oncology
- Pathology
- Genetics
Background
- Current HER2 testing guidelines for multifocal and multicentric breast cancer (MMBC) may miss HER2-low/ultralow expression by focusing only on the main tumor.
- This can lead to underdetection and missed treatment opportunities with targeted therapies like trastuzumab deruxtecan.
Purpose Of The Study
- To investigate the heterogeneity of HER2 expression across different foci in MMBC.
- To evaluate the clinical utility of current HER2 testing strategies in MMBC.
Main Methods
- Retrospective analysis of invasive cancer foci specimens from 490 MMBC patients.
- Individual HER2 testing and evaluation performed on each separate tumor focus.
Main Results
- HER2 discordance was observed in 4.0% of cases using binary classification (HER2-positive/negative).
- When stratifying HER2-negative cases (HER2-null, HER2-ultralow, HER2-low), 23.7% showed heterogeneity, with the main focus not always highest (12.0%).
- Only 11.0% of cases had all foci as HER2-null.
Conclusions
- Significant intertumoral HER2 expression heterogeneity exists in low expression levels across MMBC foci.
- Comprehensive HER2 testing on all tumor foci is essential in MMBC.
- Testing all foci is recommended regardless of histological similarity for accurate HER2 assessment.
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