EPCAM and hepatocellular carcinoma: By the evaluation of EpCAM/CD90 staining in BMP9‐high/‐low HCC specimens (Fig. S2A,B), we found that EpCAM‐positive ratio is higher in BMP9‐high HCC than that in BMP9‐low HCC, while there is no difference in CD90‐positive ratio between BMP9‐high HCC and BMP9‐low HCC (Table 1).