Precision detection of HER2-low expression in breast cancer in China:insights from a national pathologists survey
Purpose To investigate the challenges associ-ated with HER2-low in breast cancer across hospitals of varying regions and grades in China.Drawing on the findings from this investigation,this study will integrate relevant clinical guide-lines,consensus statements,and literature advancements from both domestic and international sources to offer insights for de-veloping guidelines for HER2 detection in Chinese breast cancer cases.Methods The questionnaire implementation method was Tencent WeChat as the carrier and online survey in the form of electronic questionnaire.Results According to the annual HER2 testing results of various medical institutions,compared with HER2 immunohistochemistry(IHC)scores of 3+,HER2 IHC scores of 1+or 2+significantly increased in the proportion range of over 20%(P<0.001).A total of 854 pathologists provided effective feedback for this survey,55.6%reported dif-ficulties in distinguishing between a score of 0 and 1+in certain cases,primarily due to issues related to staining percentage(83.4%)and the absence of an objective standard for weak staining(78.3%).Regarding testing procedures,417(50.5%)medical institutions used only HER2 IHC 3+as an external control,whereas 139(16.8%)set up a gradient of ex-ternal controls for HER2 IHC scores of 0,1+,2+,and 3+.68.5%of pathologists routinely adhered to the microscope mag-nification rule to assist in HER2 scoring.51.9%of pathologists support a three-category reporting model for HER2 status(nega-tive/low/positive).In cases exhibiting heterogeneity,56.3%of pathologists would accept reporting the percentages of different HER2 scores(0/1+/2+/3+).Conclusion The proportion of breast cancer patients with HER2-low is relatively high in China.Currently,there is no consensus on quality control stand-ards for the pathological diagnosis and testing procedures for HER2-low.Key diagnostic challenges include defining the lower limit of interpretation standards,standardizing testing proce-dures,establishing external controls,refining interpretation methods,and standardizing reporting practices.Given the publi-cation of the DESTINY-Breast06 study results during the revision period,there is an urgent need to develop a new edition of the Chinese guidelines for HER2 testing in breast cancer to provide clearer and more specific strategies.