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Case Reports
. 2021 Mar 1;60(5):739-744.
doi: 10.2169/internalmedicine.5754-20. Epub 2020 Sep 30.

Type 1 Autoimmune Pancreatitis Extending along the Main Pancreatic Duct: IgG4-related Pancreatic Periductitis

Junya Sato  1 , Hiroyuki Matsubayashi  1   2 , Hirotoshi Ishiwatari  1 , Tatsunori Satoh  1 , Junichi Kaneko  1 , Kazuma Ishikawa  1 , Masao Yoshida  1 , Kohei Takizawa  1 , Yohei Yabuuchi  1 , Yoshihiro Kishida  1 , Kenichiro Imai  1 , Kinichi Hotta  1 , Katsuhiko Uesaka  3 , Keiko Sasaki  4 , Hiroyuki Ono  1
Affiliations
Case Reports

Type 1 Autoimmune Pancreatitis Extending along the Main Pancreatic Duct: IgG4-related Pancreatic Periductitis

Junya Sato et al. Intern Med. .

Abstract

We herein report a unique form of autoimmune pancreatitis (AIP) spreading along the main pancreatic duct (MPD). A 70-year-old man was referred for a small lesion at the pancreatic neck, accompanying an adjacent cyst and dilated upstream MPD. Four years earlier, health checkup images had shown a pancreatic cyst but no mass lesion. Endoscopic ultrasonography showed a contrast-enhanced, tumorous lesion, mainly occupying the MPD. With a preoperative diagnosis of ductal neoplasms mainly spreading in the MPD, Whipple's resection was performed. The resected specimens showed MPD periductitis with IgG4-related pathology, indicating type 1 AIP. Clinicians should practice caution concerning the various AIP forms.

Keywords: IgG4; autoimmune pancreatitis; diagnosis; intraductal neoplasms; periductitis.

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Conflict of interest statement

The authors state that they have no Conflict of Interest (COI).

Figures

Figure 1.
Figure 1.
Health checkup images two years before the referral. Abdominal US (a) and MRCP (b) showing a unilocular cyst at the pancreas body without MPD dilation.
Figure 2.
Figure 2.
CT (70 s after contrast injection) showing an enhanced mass lesion at the pancreatic neck (arrow) adjacent to the cystic lesion (thin arrow) (a). Diffusion-weighted MRI demonstrating a mass lesion with decreased diffusion capacity and an upstream cyst (b). MRCP demonstrating non-visualized MPD at the pancreatic head and the irregularly dilated upstream duct (c). However, CT demonstrated no mass lesion upstream of the atrophic pancreas (d).
Figure 3.
Figure 3.
Ultrasonographic views. Horizontal view of abdominal US showing a low-echoic mass lesion in the MPD (a). EUS showing thickened MPD walls (thin arrows) downstream of the mass (asterisk) extending in the MPD (dot) (b) and a low-echoic mass at the pancreas neck inside the MPD (small arrows) (c) with contrast enhancement (d).
Figure 4.
Figure 4.
Endoscopic retrograde pancreatography showing MPD stenosis (arrows).
Figure 5.
Figure 5.
Pathology of the resected pancreas. Macroscopic view of the main lesion. (A to O are lined up from pancreatic head to body, with arrows indicating the MPD, arrowheads indicating the common bile duct, and an asterisk indicating a pancreatic cyst lesion) (a). A schematic illustration indicating the pathological extent of the IgG4-related lesion marked in pink and the upstream atrophic pancreas with proliferated fibrous tissues marked by crosses (×) (b). Low-powered view of Hematoxylin and Eosin (H&E) staining showing periductitis with abundant inflammatory cells infiltration around the MPD near the cyst (asterisk) (c). Pathological findings of storiform fibrosis (H&E staining, ×100) (d), obliterate phlebitis (Elastica van Gieson, ×40) (e), and rich IgG4-positive cell infiltration (IgG4, ×200) (f), meeting the criteria for type 1 AIP.
See this image and copyright information in PMC

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