Long-term Follow-up of Intraductal Papillary Mucinous Neoplasm of the Pancreas With Ultrasonography

Background & Aims: Most intraductal papillary mucinous neoplasms of the pancreas (IPMNs) have a favorable prognosis. This study was undertaken to clarify the clinical course of IPMNs and to set the criteria for surgical treatment on the basis of long-term follow-up by periodic transabdominal ultrasonography (US). Methods: Eighty-one patients with IPMN were periodically subjected to US (>3 years); 27 were reviewed retrospectively (12 with benign neoplasms [adenoma, borderline] and 15 with malignant tumors [carcinoma in situ, invasive cancer]) and 54 prospectively. US examination was focused on the main pancreatic duct (MPD) diameter, cyst diameter, and presence or absence and height of the protruding lesion. Differences between the benign and malignant groups were examined to set the criteria for surgical treatment. Follow-up results of prospective patients were investigated. Results: The increase of the MPD or the cyst diameter was significantly greater in the malignant group (P < .01). Maximum increases of the MPD diameter by 2.2 mm/year, the cyst diameter by 11.3 mm/year, and emergence or increase of the height of the protruding lesion by 3.3 mm/year were predominantly observed in the malignant group (accuracy, 90.9%, 81.3%, and 81.5%, respectively). The majority of the prospective patients showed no significant changes of these parameters; however, 2 patients (3.7%) were operated on, with the post-surgery histopathologic diagnosis of cancer. Conclusions: Periodic imaging follow-up is useful to detect a malignant IPMN. Changes in MPD diameter, cyst diameter, and/or size of the protruding lesion are the practical criteria for selecting surgery.