Predictors of Malignancy in "Pure" Branch-Duct Intraductal Papillary Mucinous Neoplasm of the Pancreas without Enhancing Mural Nodules on CT Imaging: A Nationwide Multicenter Study

Abstract

Background/AimsPresence of enhanced mural nodules, which can be visualized using computed tomography (CT), is one of high-risk stigmata in branch-duct intraductal papillary mucinous neoplasms (BD-IPMNs). Conversely, the absence of enhanced mural nodules on preoperative imaging does not exclude malignant risk. The present study aimed to investigate other morphological features as predictors of malignancy in “pure” BD-IPMNs without enhanced mural nodules on CT.MethodsThis retrospective study included 180 patients with surgically confirmed “pure” BD-IPMNs of the pancreas and no enhanced mural nodules on preoperative CT. The study was conducted at 15 tertiary referral centers throughout South Korea. Univariate and multivariate analyses were used to identify significant predictors of malignancy.ResultsBD-IPMNs with low-grade (n=84) or moderate-grade (n=76) dysplasia were classified as benign; those with high-grade dysplasia (n=8) or invasive carcinoma (n=12) were classified as malignant. The multivariate analysis revealed that cyst size ≥30 mm (odds ratio, 8.6; p=0.001) and main pancreatic duct diameter ≥5 mm (odds ratio, 4.1; p=0.01) were independent risk factors for malignancy in “pure” BD-IPMNs without enhanced mural nodules on CT. Endoscopic ultrasound detected enhanced mural nodules (6/82) that had been missed on CT, and two IPMNs with enhanced mural nodules were malignant.ConclusionsIn patients with “pure” BD-IPMNs who have no enhanced mural nodules on CT, cyst size ≥30 mm and main pancreatic duct diameter ≥5 mm may be associated with malignancy.

Factors Predictive of Malignancy Potency in Pure Branch Duct Intraductal Papillary Mucinous Neoplasm of the Pancreas without Mural Nodules

“…Cyst size and MPD dilatation were associated with malignancy in pure BD-IPMN without MNs. 6 Therefore, a cyst diameter ≥30 mm and MPD diameter ≥5 mm were associated with malignancy in pure BD-IPMNs, that is, those lacking enhanced MNs on CT. In pure type BD-IPMN, these findings may give a good direction for the plan of management.…”

“…Regarding efficacy of EUS in the study of Kim et al ., 6 EUS was able to detect MNs that had been missed by CT in six patients (7.3%), of whom two (33.3%) had malignant IPMNs. The rate of malignant IPMNs was 5.3% among the patients who had cysts without MNs on EUS.…”

“… 4 However, the management and follow-up of pancreatic cystic tumors are still controversial. This study 6 was based on the 2012 ICG for BD-IPMN, in which dilated main pancreatic ducts (MPDs) (5 to 9 mm in diameter) and cyst diameter ≥30 mm were reclassified as worrisome features. In the 2017 revised ICG, the high-risk stigmata of malignancy were revised as follows: obstructive jaundice in a patient with a cystic lesion of the pancreatic head, enhancing mural nodules (MNs) >5 mm, and MPD diameter >10 mm.…”

“…This result will enable prediction of malignancy and assessment of risk factors in patients with pure BD-IPMN without MNs or solid masses on computed tomography (CT) imaging. 6 Definite detection of true MNs or solid masses is usually difficult, particularly smaller lesions, therefore cyst size and the presence of ductal dilatation are still important findings for decision making on the appropriateness of surgery. A cyst diameter >3 cm, the presence of enhancing MNs on CT, and MN >5 mm on endoscopic ultrasonography (EUS) are independent predictors of malignancy in patients with BD-IPMNs in their previous report; 7 these findings are similar to other reports.…”

“…Multivariate logistic regression analyses revealed that the presence of MNs on EUS was a significant predictor of BD-IPMN malignancy (OR, 9.0; p=0.02). 6 Kobayashi et al . 8 reported that BD-IPMN patients with MNs <10 mm in height should undergo observation rather than resection.…”