Invasive ductal adenocarcinoma of the remnant pancreatic body 9 years after resection of an intraductal papillary-mucinous carcinoma of the pancreatic head: a case report and comparison of DNA sequence in K-ras gene mutation.

Recently, there have been a few case reports of invasive ductal adenocarcinoma (IDC) developed in the remnant pancreas after partial pancreatectomy for intraductal papillary-mucinous neoplasm (IPMN). It is necessary to clarify their histogenetic relationships among two sporadic tumors and their surrounding duct epithelium and it would be more reliable if genetic analysis is added to the conventional histology. We report a 76-year-old woman who received pancreaticoduodenectomy for IPMN with a focal in situ carcinoma (IPMC), which was transitional to the surrounding duct epithelium with papillary proliferation and a wide variety of dysplasia. Nine years after the operation, she died of IDC in the remnant pancreatic body and its surrounding duct epithelium consisted of hyperplastic mucous cells with slight-mild dysplasia. Analysis of K-ras mutation at codon 12 (wild-GGT) by direct sequencing after polymerase chain reaction indicated that their transitioning patterns differed from each other: CGT in IPMC; no mutation in the mildly dysplastic duct epithelium around IPMC; GAT in IDC of the remnant pancreas; and AGT in mucous cell hyperplasia with mild dysplasia close to the IDC. This is the first report in which the DNA sequence of K-ras mutation was determined for the two sporadic pancreatic cancers and surrounding duct changes. The following two suggestions are made: (1) the cell-origin might have differed between the two types of cancer (IDC and IPMC); and (2) no precursor lesion toward IDC or IPMC was identified in their surrounding duct epithelium.