Patients

Clinicopathologic data of ampullary adenocarcinoma patients who underwent curative pancreaticoduodenectomy in the Cancer Hospital, Chinese Academy of Medical Sciences, between 1998 and 2020 were retrospectively collected as the training cohort. We then excluded some patients according to the following criteria: i) patients diagnosed with neuroendocrine tumors, adenoma, and other rare tumor types; ii) patients with zero regional lymph node examined; iii) death within a month after the operation due to complications and other reasons; and iv) patients with missing or incomplete clinicopathologic information. In total, 264 patients were enrolled in the training cohort.

Persistent data of AC patients in the SEER database between 2010 and 2018 were obtained as validation cohort using the SEER * State v8.3.6 tool on July 8, 2021. Selection items were as follows: i) primary site—labeled = “C24.1-Ampulla of Vater”; ii) ICD-O-3 Hist/behav = “/3: adenocarcinoma, NOS”; and iii) diagnostic confirmation = “Microscopically confirmed.” The main exclusion criteria were as follows: i) AC was not the first primary malignant tumor; ii) patients did not receive pancreaticoduodenectomy; iii) patients with zero regional lymph node examined; and iv) some important information was unknown, such as staging, tumor size, number of regional lymph nodes examined, and number of LNM. Eventually, a total of 199 patients were included in the validation cohort.