Histological Subtypes Might Help Risk Stratification in Different Morphological Types of IPMNs: Back to the Future?

<b>Background:</b> Intraductal papillary mucinous neoplasms (IPMNs) display four histological subtypes: gastric foveolar, pancreaticobiliary, intestinal, and oncocytic. All of these subtypes harbor a different risk of cancer development. The clinical impact of these subtypes concerning the occurrence of high-grade dysplasia (HGD)/cancer (C) in specific morphological types, such as branch-duct (BD), main-duct (MD), and mixed-type (MT) IPMNs, has been less investigated. Hence, our aim was to investigate the prevalence of histological subtypes and their possible association with HGD/C concerning morphologically different IPMNs. <b>Methods:</b> This was a retrospective review of demographics, risk factors, and histological features in a surgical cohort of patients having undergone resection for suspect malignant IPMNs at a high-volume tertiary center from 2007 to 2017. <b>Results:</b> A total of 273 patients were resected for IPMNs from during the study period, of which 188 were included in the final analysis. With sex- and age-adjusted multivariable logistic regression analysis across the entire cohort, gastric foveolar subtypes were associated with a reduced prevalence of HGD/C (OR = 0.30; 0.11-0.81, 95% CI, 95%CI; <i>p</i> = 0.01). With univariable logistic regression analysis, in the BD-IPMN subgroup, the pancreaticobiliary subtype was associated with an increased prevalence of HGD/C (OR = 18.50, 1.03-329.65, 95% CI; <i>p</i> = 0.04). In MD- and MT-IPMNs, the gastric foveolar subtype was associated with a decreased prevalence of HGD/cancer (OR = 0.30, 0.13-0.69, 95% CI; <i>p</i> = 0.004). <b>Conclusions:</b> In MD and MT-IPMNs, the gastric-foveolar subtype is associated with a lower prevalence of HGD/C, possibly identifying in such a high-risk group, a subgroup with more indolent behavior. In BD-IPMNs, the pancreaticobiliary subtype is associated with a higher prevalence of HGD/C, conversely identifying among those patients, a subgroup deserving special attention.