Purpose: This study examined the relationship between the MIB-1 labeling index (Ki67) and the four morphological and immunohistological subtypes of intraductal papillary-mucinous neoplasms of the pancreas (IPMN).Methods: Between 2000 and 2007, we retrospectively evaluated 46 patients who had undergone surgery, were histopathologically diagnosed as IPMN, and in whom immunohistochemical staining was possible.Results: Histological grades of the 46 IPMNs were adenoma (n = 27), carcinoma in situ (n = 9), and invasive carcinoma derived from IPMN (n = 10). The morphological and immunohistological subtypes were gastric (n = 20), intestinal (n =15), panacreatobiliary (n = 9), and oncocytic (n = 2). The overall MIB-1 labeling index was 8.63% ± 9.16%. The MIB-1 labeling index of the gastric type was 3.99 ± 6.78%, which was significantly less than that of the intestinal (11.83 ± 8.95%) and pancreatobiliary (11.30 ± 10.35%) types. The MIB-1 labeling index of patients with adenoma and the gastric type was less than that for patients with adenoma and the intestinal type (p = 0.04). There were no diseasespecific fatalities in patients with an MIB-1 labeling index of <10%, whereas in those with an index of ? 10%, the 5-year survival rate was 61.1% and the prognosis was poor.Conclusions: gastric type IPMN have a low MIB-1 labeling index, which demonstrates that malignancy of this subtype is lower than that of other subtypes
