The Role of Intraoperative Hepatic Ultrasonography in Gastrointestinal or Pancreatic Neuroendocrine Tumor

Background: Liver metastases are common in patients with neuroendocrine neoplasms, but often underestimated by preoperative imaging. Intraoperative ultrasound (IOUS) is the reference standard for staging of primary and metastatic liver tumors, with a diagnostic accuracy superior to that of CT and MRI. Rationale: The present study aims to evaluate the contribution of IOUS to staging of liver disease in patients with neuroendocrine tumor candidates for primary tumor resection classified as cM0 at preoperative imaging. The study will collect a prospective series of 99 patients undegoing surgery for gastro-intestinal or pancreatic neuroendocrine tumor at the Humanitas Clinical Institute (coordinating centre) or at one of the participating centres in the period 2020-2023. All patients had to be cM0 tumor at preoperative imaging. Additional inclusion criteria: age\>18 years, ability to give the informed consent for study participation; no other malignancies in the previous 5 years; preoperative staging including abdominal CT and DOTATOC PET-CT performed ≤60 days before surgery. This prospective observational multicentre study aims to elucidate the proportion of patients with gastro-intestinal or pancreatic neuroendocrine tumor cM0 at preoperative imaging that have intraoperative detection of liver metastases at IOUS. Primary endpoint: \- Performances of IOUS in identifying liver metastases in patients with neuroendocrine tumor classified as cM0 at preoperative imaging Secondary endpoints: * Impact of IOUS on the therapeutic strategy * Performances of preoperative imaging (CT, MRI and PET-CT) in comparison with those of IOUS The study will collect a prospective series of 99 patients undergoing surgery for gastro-intestinal or pancreatic neuroendocrine tumor at the Humanitas Clinical Institute (coordinating centre) or at one of the participating centres in the period 2020-2023. The study includes the following steps: Preoperative / enrollment: All patients candidat