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Protein Plug in the Pancreatic Duct Mimicking Pancreatic Adenocarcinoma

Yamaguchi, Takeru MD1; Kadowaki, Yoshihiko MD, PhD2; Okino, Takeshi MD, PhD3; Uehara, Eriko MD1; Ohmori, Mika MD1; Mori, Takeki MD, PhD1

doi: 10.14309/crj.0000000000000147

1Department of Radiology, Japanese Red Cross Kobe Hospital, Hyogo, Japan

2Department of Surgery, Japanese Red Cross Kobe Hospital, Hyogo, Japan

3Department of Pathology, Japanese Red Cross Kobe Hospital, Hyogo, Japan

Correspondence: Takeru Yamaguchi, MD, Department of Radiology, Japanese Red Cross Kobe Hospital, 1-3-1 Wakinohamakaigan-dori, Kobe-shi Chuo-ku, Hyogo, Japan, 651-0073 (

Received February 05, 2019

Accepted April 04, 2019

Online date: August 2, 2019

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

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A 68-year-old man who had histologically proven lung cancer presented to our hospital for the further examination. He consumed 180 g of ethanol a day. The serum level of amylase was normal. Tumor markers were within the normal range; carcinoembryonic antigen, 1.7 ng/mL; and carbohydrate antigen 19-9, 8.1U/mL. Dynamic contrast-enhanced computed tomography for staging of the lung cancer accidentally revealed an ill-defined hypoattenuating lesion in the pancreatic head. The lesion was slightly enhanced during the arterial phase and the portal phase (Figure 1). There was no evidence of lymphadenopathy or metastasis. Abdominal ultrasonography demonstrated a hypoechoic mass measuring 9 mm in diameter in the pancreatic head. Dynamic contrast-enhanced magnetic resonance imaging also showed a mass with slight enhancement in the pancreatic head. Magnetic resonance cholangiopancreatography revealed no dilatation or narrowing in the main pancreatic duct. Given the high suspicion of pancreatic cancer, subtotal stomach-preserving pancreaticoduodenectomy was performed after lung lobectomy for the lung cancer. The cut surface of the resected specimen demonstrated a hard white mass in the pancreatic head (Figure 2). Histology proved the specimen to be an impacted protein plug in the branch duct without evidence of malignancy (Figure 3). Otherwise, there was no evidence of chronic pancreatitis although minimal lymphocyte infiltration and fibrosis was observed only around the protein plug.

Figure 1

Figure 1

Figure 2

Figure 2

Figure 3

Figure 3

Protein plug obstruction of the pancreatic duct is one of the early events in chronic pancreatitis.1 It is hypothesized that a protein plug is formed because of hypersecretion of protein, which is not compensated for by an increase in ductal bicarbonate secretion.2 The protein plug in our patient showed the findings on imaging examinations to be similar to those of pancreatic adenocarcinoma, which is known to manifest as a hypovascular mass with poorly defined margins on computed tomography.3 A previous report revealed that a protein plug causing the dilation of the main pancreatic duct can be difficult to be differentiated from pancreatic cancer with concomitant intraductal papillary mucinous neoplasm.4 In our case, however, it is considered that the protein plug did not result in ductal dilatation because it was formed in the branch duct. This case provided an important clinical suggestion. Protein plug should be considered as a differential diagnosis of pancreatic carcinoma, especially in the patient with a background of chronic pancreatitis or alcoholic abuse.

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Author contributions: T. Yamaguchi wrote the manuscript. Y. Kadowaki, T. Okino, E. Uehara, and M. Ohmori reviewed the manuscript. T. Mori reviewed the manuscript and is the article guarantor.

Financial disclosure: None to report.

Informed consent was obtained for this case report.

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1. Sarles H, Bernard JP, Johnson C. Pathogenesis and epidemiology of chronic pancreatitis. Annu Rev Med. 1989;40:453–68.
2. Sahel J, Sarles H. Modifications of pure human pancreatic juice induced by chronic alcohol consumption. Dig Dis Sci. 1979;24(12):897–905.
3. Lu DS, Vedantham S, Krasny RM, Kadell B, Berger WL, Reber HA. Two-phase helical CT for pancreatic tumors: Pancreatic versus hepatic phase enhancement of tumor, pancreas, and vascular structures. Radiology. 1996;199(3):697–701.
4. Ichikawa K, Hattori K, Kusafuka T, et al. [Case of protein plug in the pancreatic duct mimicking pancreatic cancer concomitant with branch-type intraductal papillary mucinous neoplasm]. Nihon Shokakibyo Gakkai Zasshi. 2017;114(12):2151–7. Japanese.
© 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The American College of Gastroenterology.