Clinicopathologic Study of the MIB-1 Labeling Index (Ki67) and Postoperative Prognosis for Intraductal Papillary Mucinous Neoplasms and Ordinary Ductal Adenocarcinoma

Abstract

Intraductal papillary mucinous neoplasms (IPMNs) are pathologically classified as IPMN with low- or intermediate-grade dysplasia, IPMN with high-grade dysplasia, and IPMN with an associated invasive carcinoma. A stepwise carcinogenic pathway has been considered for IPMN. However, it is not obvious when surgical resection should be performed for IPMN. We studied the MIB-1 labeling index in cases of IPMN and ordinary ductal adenocarcinoma (ODA). Moreover, IPMN with an associated invasive carcinoma was divided into 2, namely, carcinoma in situ and invasive components, and the respective MIB-1 labeling indexes were examined. The MIB-1 labeling index for IPMN with low- or intermediate-grade dysplasia (1.8%) was significantly lower than those for IPMN with high-grade dysplasia (14.2%), both the carcinoma in situ components (23.1%) and invasive components (19.2%) within the IPMN with an associated invasive carcinoma, and ODA (19.5%; P < 0.0001).The 5-year survival rates after resection were 100% for IPMN with low- or intermediate-grade dysplasia, 83.3% for IPMN with high-grade dysplasia, 53.8% for IPMN with an associated invasive carcinoma, and 10.3% for ODA. MIB-1 might be useful for the classification of malignant potential in IPMN. Intraductal papillary mucinous neoplasm should be surgically resected when the tumor is diagnosed as IPMN with high-grade dysplasia.