Lateral spread along the main pancreatic duct in branch-duct intraductal papillary-mucinous neoplasms of the pancreas: usefulness of intraductal ultrasonography for its evaluation.

Background: Intraductal papillary mucinous neoplasms (IPMN) of the pancreas tend to spread intraepithelially along the pancreatic duct wall. We evaluated histopathological intraductal lateral spread (LS) along the main pancreatic duct (MPD) from branch-duct IPMN and investigated the usefulness of intraductal ultrasonography (IDUS) for its preoperative diagnosis.

Patients And Methods: Twenty-four patients with branch-duct IPMN who had undergone preoperative IDUS and surgery were reviewed clinicopathologically. The prevalence and histological length of LS along the MPD from branch-duct IPMN, characteristics of the patients with LS, and efficacy of LS assessment by IDUS were examined.

Results: LS along the MPD was observed in 54% of the subjects. In the group of patients with LS, its mean length was 25.2±16.8mm (5-50mm) and the diameter of the MPD was 6mm or greater. Of the patients with LS, those in whom the length of LS along the MPD was longer than the diameter of the cystically dilated branch accounted for 30%. The diameter of the MPD in the group with LS was significantly greater than that in the group without LS (P=0.03). The sensitivity, specificity, and overall accuracy of IDUS in the detection of LS were 92%, 91%, and 92%, respectively.

Conclusion: LS along the MPD was detected in about half of the resected cases of branch-duct IPMN. Preoperative transpapillary IDUS may be beneficial for the determination of the resection line, especially in those branch-duct IPMN patients in whom the MPD is 6 mm or greater in diameter.