What is it about?

The current definition of HER2-low Breast cancer remains incomplete with low rates of interobserver concordance. This study aims to refine the HER2-low definition with emphasis on distinguishing HER2 score 0 from score 1+ to identify patients who are eligible for ADC.

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Why is it important?

After antibody-drug conjugate (Trastuzuman-deruxtecan) being approved for the treatment of HER2 low breast cancer patients, distinguishing patients that are HER2 IHC 1+ from IHC 0 became inevitable. This is the first study that refines the definition of HER2 1+ using HER2 RNA level and artificial neural network model with high interobserver concordance achieved.


Our refined criteria aimed to complete all the missing scenarios for HER2 scoring in breast cancer with emphasise on the HER2 low category. We believe that the application of our refined criteria will guarantee high concordance rates for HER2 scoring among pathologists. Also, it will help in the identification of HER2 low patients who are fit for treatment with the new antibody-drug conjugate.

Nehal Atallah
1Division of Cancer and Stem Cells, School of Medicine, the University of Nottingham and Nottingham University Hospitals NHS Trust, Nottingham, UK,

Read the Original

This page is a summary of: Refining the definition of HER2 ‐low class in invasive breast cancer, Histopathology, September 2022, Wiley,
DOI: 10.1111/his.14780.
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