O2–023 - The Clinical Features of Branch Duct Type Ipmns of the Pancreas with Classification of Histological Subtypes

Abstract

Background: Intraductal papillary mucinous neoplasms (IPMNs) of the pancreas are divided into two types, the main duct type and the branch duct type. Generally, the branch duct type grows slowly and has a good prognosis compared to the main branch type. According to International consensus guidelines for the management of IPMN, if lesion is < 10mm in size, the interval between follow-up examination would appear reasonable to be every 2-3 years. However, there were reportedly some cases of the branch duct type IPMNs were known to show rapidly growing and progression to malignancy. Recently, IPMNs of the pancreas are classified into 4 types-gastric (G type), intestinal (I type), pancreatobiliary (PB type), and oncocytic (O type) on the basis of their morphology and immunohistochemistry. The G types and I types are known to have less malignant potential than that of the PB type, and invasive carcinomas derived from two types is known to be less invasive and slower growing than those derived from the PB type. But we have had no minute examination of the clinical features of each type. So, we investigated the resected cases of 22 patients with branch duct type IPMNs, which were classified into 4 types and compared with the speed of cystic lesion with IPMNs and the frequency of invasive carcinoma of each type. Methods: We classified the 22 patients with branch duct type IPMNs resected between January 2005 and February 2012 in our institutes, into 4 types on the basis of their morphology and immunohistochemistry, and revealed the speed of cystic lesion with IPMNs and the frequency of invasive carcinoma of each type. Results: Fifteen patients (68%) were G type, 4 patients (18%) were I type, 3 patients (14%) were PB type. There is no patient of O type. Their median age was 73.2 years (range 57-84), 77 years (range 64-84), and 71.3 years (range 59-79), respectively. The frequency of invasive adenocarcinoma derived from IPMN was 2/15 (13%), 1/4 (25%), and 3/3 (100%) respectively. The growing speed of cystic lesion of patients who could be observed over 1 year (mean ± SD mm/year) was 3.0 ± 0.9, 3.54 ± 1.6, and 15.2 ± 9.2 respectively (p < 0.05). Conclusion: PB type showed rapid growing and high frequent progression to malignancy compared to G and I type. Our findings suggest that PB type should be followed for shorter period.