Intraductal papillary mucinous neoplasm in an annular pancreas: a case report
© Kobayashi et al. 2015
Received: 4 February 2015
Accepted: 7 August 2015
Published: 25 August 2015
Annular pancreas is a rare anomaly in which a ring of pancreatic tissue encircles the second portion of the duodenum. We herein report a case involving a 79-year-old Japanese man with an intraductal papillary mucinous neoplasm (IPMN) of the pancreas. Imaging studies showed that the pancreatic tissue encircled the descending part of the duodenum and that a 30-mm-diameter cystic tumor was present in the annular segment, leading to the diagnosis of pancreatic IPMN. Limited pancreatic resection was successfully performed by careful division of the annular segment from the second portion of the duodenum. The postoperative course was uneventful, and the patient’s pancreatic function was retained without the need for supplementation. To the best of our knowledge, this is the first report of IPMN occurring in the annular segment of the pancreas. Limited resection of the pancreatic annular segment is a feasible surgical treatment for noninvasive IPMN of the annular pancreas.
Annular pancreas is a rare congenital anomaly caused by malrotation of the pancreatic ventral bud during embryonic development. This condition was first reported by Tiedemann in 1818 . Autopsy and intraoperative studies have estimated the incidence of annular pancreas to be approximately 5 to 15 cases per 100,000 patients . The coexistence of an annular pancreas with a pancreatic neoplasm is therefore exceptionally rare.
We herein report a case of an intraductal papillary mucinous neoplasm (IPMN) in an annular pancreas.
The literature of pancreatic neoplasm associated with annular pancreas
Matsusue et al. 
Kamisawa et al. 
Yasui et al. 
Ben-David et al. 
Cholet et al. 
Ijichi et al. 
Milone et al. 
Limited pancreatic resection
IPMNs are characterized by cystic dilation of the main and/or branched pancreatic ducts and intraductal proliferation of neoplastic mucinous cells arranged into papillary structures [17, 18]. These tumors have a wide spectrum of atypical grades ranging from low-grade dysplasia to invasive carcinoma . The diagnosis of IPMN of the pancreas has markedly increased in the last few decades because of the widespread use of high-resolution imaging [20, 21]. IPMNs are classified as main duct type, branch duct type, and combined type, according to the area of involvement of the pancreatic ductal system [22, 23]. The present patient had a branch duct type of IPMNs (adenoma) with low-grade malignancy [22, 23]. However, the patient experienced abdominal pain, and the diameter of the tumor was large (30 mm). Although there is a controversy regarding whether pancreatic resection or close follow-up should be performed to treat IPMNs with low-grade malignant potential, especially in cases similar to the present case, we performed surgical extirpation of the tumor according to the Sendai consensus guidelines [21–26].
Various operative procedures are available to treat IPMNs with a low risk of malignancy [27–30]. Nakagohri et al. reported good surgical outcomes for noninvasive or minimally invasive IPMNs after inferior pancreatic head resection . In this procedure, the uncinate process and pancreatic parenchyma around the duct of Wirsung are resected, preserving the pancreatic head around the duct of Santorini . Takada described ventral pancreatectomy, which involves resection of only the ventral segment of the pancreas, preserving the dorsal segment and the main pancreatic duct . Of course, division of the annular segment is generally not recommended because of the high incidence of postoperative complications such as fistula formation, pancreatitis, pancreatic laceration, and/or recurrent duodenal stenosis secondary to local fibrosis [5, 33, 34]. Thus, in the present case, the resection area was very carefully determined, and an additional procedure was performed to avoid postoperative complications.
In many cases, the pancreatic annulus cannot be separated because of the dense adhesion between the duodenum and annulus . In our case, however, the adhesion between the annular segment and second portion of duodenum was fortunately loose, and we easily ligated the annular pancreatic duct. The annular segment (including the tumor) was removed, and the pancreatic head around the duct of Santorini was preserved. Additionally, the second portion of the duodenum and the pancreatic stump were covered by the jejunum to prevent duodenal leakage and pancreatic fistula formation. The present case suggests that limited annular pancreatic resection is safe when the adhesion between the duodenum and annular segment is loose and the locations of the annular pancreatic duct and the duct of Santorini are definitively identified. However, the precise indications for this procedure remain to be elucidated.
In conclusion, the possibility of coexisting pancreatobiliary disorders such as IPMNs should be kept in mind in adult patients with an annular pancreas. Partial resection of the pancreas, including division of the annular segment, may be safe and effective in selected patients.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images.
The authors thank Amane Kitasato, Tomohiko Adachi, and Shinya Onizuka for their constructive advice.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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