Predictors of malignancy and natural history of main-duct intraductal papillary mucinous neoplasms of the pancreas.

Objectives: Because the prevalence of carcinoma is high in main-duct intraductal papillary mucinous neoplasms (IPMNs) of the pancreas, surgical resection is recommended for all main-duct type IPMNs. This study aimed to investigate the clinical predictors of malignancy and natural history of main-duct IPMNs. Methods: Preoperative clinical characteristics reliably correlated with malignancy in 26 surgically resected patients with main-duct IPMN, and long-term outcome in 20 conservatively followed patients with main-duct IPMN was examined. Results: Age at diagnosis was significantly older in conservatively followed IPMN patients than in surgically resected IPMN patients. Main pancreatic duct (MPD) dilatation 10 mm or greater and mural nodules were significantly more frequent in malignant IPMNs. Obvious progression of dilatation of the MPD was detected in all 4 conservatively followed patients who developed invasive pancreatic carcinoma. The histology of IPMN at autopsy of 4 conservatively followed patients who died of other causes 21 to 120 months later was adenoma. Seven conservatively followed without malignant findings did not show obvious progression of MPD dilatation. Conclusions: Although surgical resection is indicated for many main-duct IPMNs, conservative follow-up may be an option for elderly asymptomatic patients with main-duct IPMNs with the MPD less than 10 mm, no obvious mural nodule, and negative cytology.