Patients and tissue preparation

We investigated 31 slabs (up to 20 × 10 × 5 mm) of extrahepatic cholangiocarcinoma from patients who underwent surgical resection at the Johns Hopkins Hospital or at the Asan Medical Center. Approval of the relevant institutional review boards was obtained. Twenty-nine samples were obtained at Johns Hopkins Hospital, and two were from the Asan Medical Center. Patients who received neoadjuvant chemotherapy or neoadjuvant radiation therapy were excluded.