HER2 low expression in breast cancer:a retrospective analysis

GUO Jia; YANG Wen-tao; BAI Xue-feng

doi:10.3969/j.issn.1007-8096.2025.02.002

Abstract：Objective Traditionally,only HER2 positive patients can benefit from anti-HER2 treatment.With the approval of trastuzumab deruxtecan(T-DXd)for the treatment of unresectable or metastatic HER2-low breast cancer patients,HER2-low expression has received widespread attention,and more in-depth research is urgently needed.Methods We collected invasive breast cancer cases from January 2018 to December 2022,including 580 cases of HER2-low expression and 989 cases of HER2-0 expression.A retrospective analysis of clinical pathological characteristics was carried out in this cohort.Results Among the 2030 selected samples,the overall HER2-low prevalence rate was 28.6％.There were no differences between the HER2-low group and the HER2-0 group in terms of gender,tumor size,tumor location,vascular invasion,number of lymph node metastasis cases,and axillary lymph node dissection tendency.However,the histological grading of the HER2-low subgroup was lower,with grades of Ⅰ-Ⅱ(88.3％vs 68.4％)and Ⅲ(11.7％vs.31.6％),and more patients over 50 years old.The HER2-0 group had a higher proportion of cases with Ki-67＞30％and a higher rate of conservative surgery(53.9％).The HER2 status in all the three groups of primary breast tumors and lymph node metastases,biopsy and surgical specimens,and biopsy and surgical specimens after neoadjuvant therapy showed inconsistent expression(14.1％,25.4％,and 29.8％),which was commonly detected in HER2-low and HER2-0 samples.Conclusion The clinicopathological characteristics of HER2-low breast cancer and HER2-0 breast cancer patients in this region have limited differences,and more research is needed to determine the clinical significance of HER2-low.In addition,pathologists need to undergo standardized training to accurately identify patients with HER2-low expression.