Updates and Insights on Human Epidermal Growth Factor Receptor 2 (HER2) in Breast Cancer in Sohag Governorate

HER2 status is no longer simply classified as a positive or negative. It is now evaluated on a score from 0 to 3+, where score 3+ indicates HER2-positive disease because it shows strong, complete circumferential membranous staining. In the HER2-negative spectrum, score 1+ and score 2+ without gene amplification are classified as HER2-low, while score 0 involves both HER2-null cases with no membrane staining and HER2-ultralow cases with faint or weak incomplete membranous staining in ≤10%, of tumor cells. In addition, ISH can be used to determine HER2 gene amplification status. The emergence of HER2-low and also HER2-ultralow concepts has challenged the traditional binary framework and increased the need for collective reporting. As a result, careful interpretation of delicate staining patterns, reproducible scoring and appropriate use of complementary testing methods are now central to accurate HER2 classification in both primary and metastatic breast cancer.