Onkológia 2/2024

New approaches in the testing of HER2 status in the biopsies of breast carcinoma patients

The identification of HER2 positivity represents a traditional predictive biomarker for anti-HER2 therapy. In this review article we summarize new requirements on HER2 testing of biopsy specimen of breast cancer patients, Although previously less attention has been paid to HER2 negativity, the new theraeutical modalities published in some clinical studies highlight the importance of a precise HER2 evaluation of all breast cancers. In this article the attention has been paid to the detailed description of the HER2 analyses using a combination of the imunohistochemical and in situ hybridization methods, as well as to the precise evaluation and reporting of the HER score from 0 to 3+, incl. descriptions of the so-called HER low and HER2-ultra-low cancers. However, in agreement with recent guidelines the pathologists should continue to use the traditional evaluation of individual HER2 categories with inclusion of a detailed data on the HER2 protein expression and on the HER2 gene status resp. Contemporary level of knowledge does not support to implement the HER2-low and HER2-ultra-low categories as separate biological categories into the final biopsy report, although in clinical oncology their identification is required for the new therapeutical modalities.

Keywords: breast cancer, HER2: positivity and negativity, low and ultra-low HER2 expression