Study-specific and pooled estimates for metastasis location–specific discordance percentages for studies reporting estrogen receptor alpha (ERα), progesterone receptor (PR), and/or human epidermal growth factor receptor 2 (HER2) immunohistochemistry in primary breast tumors and paired distant metastases. Study-specific data are ordered by date of publication. Locations of metastases are grouped as follows: central nervous system, bone, liver, lung, and skin. The y-axis shows the total pooled discordance percentage of all locations. Discordance percentages are shown for total conversion of ERα (A), total conversion of PR (B), and total conversion of HER2 (C). Error bars indicate confidence intervals. Heterogeneity was assessed using I2 and Cochran’s Q. CI = confidence interval; CNS = central nervous system; df = degrees of freedom.
