Branch-duct intraductal papillary mucinous neoplasm (IPMN): Are cyst volumetry and other novel imaging features able to improve malignancy prediction compared to well-established resection criteria?

OBJECTIVES: Current guidelines base the management of intraductal papillary mucinous neoplasms (IPMN) on several well-established resection criteria (RC), including cyst size. However, malignancy may occur in small cysts. Since branch-duct (BD) IPMN are not perfect spheres, volumetric and morphologic analysis might better correlate with mucin production and grade of dysplasia. Nonetheless, their role in malignancy (high-grade dysplasia/invasive cancer) prediction has been poorly investigated. Previous studies evaluating RC also included patients with solid-mass-forming pancreatic cancer (PC), which may affect the RC yield. This study aimed to assess the role of volume, morphology, and other well-established RC in malignancy prediction in patients with BD- and mixed-type IPMN after excluding solid masses. METHODS: Retrospective ethical review-board-approved study of 106 patients (2008-2019) with histopathological diagnosis of BD- and mixed-type IPMN (without solid masses) and preoperative MRI available. Standard imaging and clinical features were collected, and the novel imaging features cyst-volume and elongation value [EV = 1 - (width/length)] calculated on T2-weighted images. Logistic regression analysis was performed. Statistical significance set at two-tails, p < 0.05. RESULTS: Neither volume (odds ratio (OR) = 1.01, 95% CI: 0.99-1.02, p = 0.12) nor EV (OR = 0.38, 95% CI: 0.02-5.93, p = 0.49) was associated with malignancy. Contrast-enhancing mural nodules (MN), main pancreatic duct (MPD) ≥ 5 mm, and elevated carbohydrate antigen (CA) 19-9 serum levels (> 37 µmol/L) were associated with malignancy (MN OR: 4.32, 95% CI: 1.18-15.76, p = 0.02; MPD ≥ 5 mm OR: 4.2, 95% CI: 1.34-13.1, p = 0.01; CA19-9 OR: 6.72; 95% CI: 1.89 - 23.89, p = 0.003). CONCLUSIONS: Volume and elongation value cannot predict malignancy in BD- and/or mixed-type IPMN. Mural nodules, MPD ≥ 5 mm and elevated CA19-9 serum levels are associated with higher malignancy risk even after the exclusion of solid masses. KEY POINTS: • Novel and well-established resection criteria for IPMN have been evaluated after excluding solid masses. • BD-IPMN volume and elongation value cannot predict malignancy. • Main pancreatic duct ≥ 5 mm, mural nodules, and elevated carbohydrate antigen 19-9 levels are associated with malignancy.

Main pancreatic duct dilation greater than 6 mm is associated with an increased risk of high-grade dysplasia and cancer in IPMN patients.

INTRODUCTION: IPMNs, considered precursor lesions of pancreatic adenocarcinoma (PDAC), might display histological alteration varying from low-grade dysplasia (LGD) to cancer. Nevertheless, the prevalence of PDAC is far below the prevalence of IPMN; therefore, not all of these precursor lesions finally progress to cancer. Preoperative features consistent with and finding at final histology of high-grade dysplasia (HGD) or cancer are currently lacking. The aim of this study is to correlate the presence of preoperative clinical features with the finding of advance lesions at final histology. METHODS: This is retrospective cohort analysis of patients who underwent surgery for histologically confirmed IPMNs at Karolinska University Hospital, from 2008 to 2015. RESULTS: MPD 6-9.9 mm and ≥ 10 mm were associated with an increased risk of HGD/cancer (respectively, OR 2.92, CI 1.38-6.20, p = 0.005 and OR 2.65, CI 1.12-6.25, p = 0.02). Preoperative high CA19.9 and jaundice were both associated with a higher risk of HGD/cancer at final histology (respectively, OR 4.15, CI 1.90-9.05, p = 0.0003 and OR 15.36, CI 1.94-121.22, p = 0.009). At sex- and age-adjusted multivariable logistic regression analysis, MPD between 6 and 9.9 mm (OR 2.64, CI 1.15-6.06, p = 0.02), jaundice (OR 12.43, CI 1.44-106.93, p = 0.02), and elevated CA19.9 (OR 3.71, CI 1.63-8.46, p = 0.001) remained associated with the occurrence of HGD/cancer. DISCUSSION: The presence of MPD dilation ≥ 6 mm, jaundice, and elevated CA19.9 in IPMN patients are consistent with the finding for HGD/cancer at final histology, thus representing possible markers of advanced lesions suitable for earlier or preventive curative surgical treatment.