Dilatation of the main pancreatic duct of unknown origin: causes and risk factors of pre-malignancy or malignancy

Introduction A dilatation of the main pancreatic duct (MPD) is mainly due to obstructive causes (pancreatic tumor, chronic pancreatitis) or intraductal papillary mucinous neoplasm (IPMN). This study aims to assess the risk of pre-malignancy or malignancy in case of MPD dilatation with no visible mass nor obstructive calcification on computed tomography scan (CT-scan) in a population operated for it. Patients and methods All patients operated on from November 2015 to December 2019 in our center for a significant dilatation of the MPD without visible obstructive cause on CT-scan were included. Preoperative work-up included at least CT-scan, magnetic resonance imaging (MRI), and endoscopic ultrasonography (EUS). Primary endpoint was the final pathological diagnosis. Secondary endpoints were predictive factors of malignancy. Results 101 patients were included, mean age 68 years-old. Final pathological data were pancreatic adenocarcinoma ( n = 2), IPMN with high-grade dysplasia ( n = 37), high-grade Pancreatic Intraepithelial Neoplasia (PanIN) ( n = 2) (total of pre-malignant or malignant lesions: n = 41), neuroendocrine tumor ( n = 6), IPMN with low-grade dysplasia ( n = 45), low-grade PanIN ( n = 5), chronic pancreatitis ( n = 3), and benign stenosis ( n = 1). On preoperative explorations, the median diameter of MPD was 7 mm [3–35]. MRI and/or EUS showed intraductal material, nodule, or cyst in 22, 32, and 52 patients, respectively; 22 patients without nodule visible on MRI or EUS had still a pre-malignant or malignant lesion. In multivariate analysis, predictive factors for pre-malignancy or malignancy were symptoms before surgery ( p = 0.01), MPD dilatation without downstream stenosis ( p = 0.046), and the presence of nodule ( p = 0.009). Conclusion A dilatation of the MPD without detectable mass or obstructive calcification on CT-scan was associated with a pre-malignant or malignant lesion in 41 patients. Symptoms before surgery, MPD dilatation without duct narrowing, and the presence of nodules on MRI/EUS were associated with the risk of pre-malignancy or malignancy.