Should we regard all main duct type intraductal papillary mucinous neoplasms of the pancreas (MD-IPMN) as an indication of surgery? -A retrospective study in 29 patients with MD-IPMN showing mural nodules.

PURPOSE: To elucidate predictive factors for malignant main duct type IPMN (MD-IPMN).

METHODS: All 29 subjects had mural nodules (MNs) in the main pancreatic duct (MPD) on preoperative endoscopic ultrasonography and underwent surgery (19, malignant; 10, benign). Possible predictive factors for malignancy such as background, imaging, and histological factors including histological subtype (HS), were evaluated.

RESULTS: Multivariate analysis revealed an MPD diameter of ≥12 mm (p = 0.042) and non-gastric type (p = 0.001) to be the statistically significant predictive factors for malignancy. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy to detect malignancy by using "an MPD diameter of ≥12 mm and/or non-gastric type" were 95%, 70%, 86%, 88%, and 86%, respectively. In 7 subjects in whom HS was preoperatively evaluated using pancreatic specimens obtained before surgery, the agreement rate of the preoperative HS with definitive HS evaluated using resected specimens was 86%.

CONCLUSIONS: For MD-IPMNs with MNs, "an MPD diameter of ≥12 mm and/or non-gastric type" are indicated for surgery. On the other hand, careful surveillance without immediate pancreatic surgery may be an option for MD-IPMNs showing both an MPD diameter of <12 mm and gastric type.