ESR1 and gallbladder cancer: It is notable that the unique pharmacokinetic characteristics make tamoxifen more advantageous in gallbladder cancer treatment.45 Tamoxifen metabolites 4‐hydroxytamoxifen and N‐desmethyl‐4‐hydroxytamoxifen, which possess a much stronger ER inhibitory activity,46 could be secreted in bile and participate in enterohepatic circulation.47, 48, 49 The bile infiltrating environment of GBC provides another platform for tamoxifen metabolites to reach tumour.