We sequenced postmortem metastatic lesions from ten rapid autopsies, including six patients with estrogen receptor-positive (ER+) breast cancer (PBr01–Br06), three patients with cholangiocarcinoma (biliary tract cancer; PBi01–Bi03), and one patient with non-small cell lung cancer (PLu01). Here, ESR1 is linked to cholangiocarcinoma.