Cystic neoplasm of the pancreas: a Japanese multiinstitutional study of intraductal papillary mucinous tumor and mucinous cystic tumor.

The Japan Pancreas Society performed a multiinstitutional, retrospective study of 1379 cases of intraductal papillary mucinous tumor (IPMT) and 179 cases of mucinous cystic tumor (MCT) of the pancreas. Clinicopathologic features and postoperative long-term outcomes were investigated. IPMT were most frequently found in men and in the head of the pancreas. In contrast, all patients with MCT were women. Ovarian-type stroma were found in only 42.2% of the MCT cases. Prognostic indicators of malignant IPMT included advanced age, positive symptoms, abundant mucous secretion, presence of large nodules and/or large cysts, remarkable dilatation of the main pancreatic duct, and main duct- or combined-type IPMT. Advanced age, positive symptoms, and presence of large nodules and/or large cysts were predictive of malignant MCT. The 5-year survival rate of IPMT patients was 98%-100% in adenoma to noninvasive carcinoma cases, 89% in minimally invasive carcinoma cases, and 57.7% in invasive carcinoma cases. The 5-year survival rate of MCT patients was 100% in adenoma to minimally invasive carcinoma cases and 37.5% in invasive carcinoma cases. In conclusion, IPMT and MCT show distinct clinicopathologic and prognostic differences. The results from this study may contribute to the diagnosis and treatment of IPMT and MCT.