Fig. 1

Clinicopathologic Characteristics according to HER2-low Status. A Frequency of HR+ disease according to HER2 phenotypes in primary and metastatic tumors. The P value was calculated by Chi-square test based on the number of cases per group featuring HR+ or HR− phenotype. Only the error bars with significant P values are shown. B Ki67 score stratified by HR and HER2 status in primary and metastatic tumors. The P value was calculated by T-test. C Distribution of HER2 status of primary and metastatic sites in the overall population, HR+ and HR− tumors. The Sankey diagram was mapped by the “ggalluvial” R package. D Absolute percentages of Fig. 1. C are reported. The P value was calculated by Chi-square test based on the number of cases per group featuring HER2-positive, HER2-low and HER2-zero phenotype. E The percentage of different HER2 statuses in HR+ and HR− subgroups of primary and metastatic breast cancer. The P value was calculated by Chi-square test based on the number of cases per group featuring HER2-positive, HER2-low and HER2-zero phenotype. amp: with HER2 gene amplification by FISH; no-amp: without HER2 gene amplification by FISH; met: metastatic; * 0.05 > p value ≥ 0.01, ** 0.01 > p value ≥ 0.001, *** p value < 0.001