Metachronous intraductal papillary mucinous neoplasms disseminate via the pancreatic duct following resection.

Metachronous development of intraductal papillary mucinous neoplasms in the remnant pancreas following resection is a significant clinical burden. Our aim was to characterize the clinicopathological and molecular features of the patients with metachronous tumor development to identify predictive factors and the possible route(s) of dissemination. Seventy-four patients who underwent resection of intraductal papillary mucinous neoplasms with no invasive compartment or associated carcinoma were retrospectively analyzed. In patients with metachronous tumor development, targeted sequencing of 18 genes associated with pancreatic tumorigenesis and immunohistochemical detection of four proteins (p53, SMAD4, p16, and β-catenin) were performed on both primary and metachronous tumors. The distributions of microscopic neoplastic lesions were examined at surgical margins and in apparently normal tissue apart from the primary tumor. During the median follow-up period of 52 months, 9 patients (12%) developed metachronous tumors in the remnant pancreas. Primary tumors located in the body/tail of the pancreas (odds ratio, 15; 95% confidence interval, 1.6-131) and of the pancreatobiliary type (odds ratio, 6.1; 95% confidence interval, 1.1-35.7) were identified as significant risk factors for subsequent metachronous tumor development. Eight of the nine patients shared molecular aberrations between their primary and metachronous tumors, suggesting migrations from the primary tumor to the pancreatic duct as the cause of metachronous tumor development. Our data suggest that these post-resection metachronous tumors develop by skip dissemination of the primary tumor, potentially via the pancreatic duct. The development of strategies to better predict and prevent this form of tumor progression is necessary.