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case_images: Computed tomography and endoscopic retrograde cholangiopancreatographyimages. Enhanced computed tomography showed stenosis in the common bile duct (arrowhead) by a poorly marginated mass around the pancreatic head (approximately 2 cm wide and 3 cm long), which also involved the second part of the duodenum (a, b). Endoscopic retrograde cholangiopancreatography showed a 5-cm distal common bile duct stricture and dilated common and intrahepatic bile ducts (c).
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case_images: Endoscopic retrograde cholangiography revealed a 5-cm distal CBD stricture and dilated common and intrahepatic bile ducts (Figure 1a-c).
case_images: Duodenal images on the initial endoscopy. (a) A stenosed lumen with uneven and heterogeneously hypertrophied mucosa in the superior duodenal flexure. (b, c) A post-bulbar duodenal ulcer with an irregular margin spread to the oral side of the papilla of Vater (arrowhead). (d) The oral protrusion is reddish and swollen.
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case_images: The lesion margin was irregular, suggesting intraluminal invasion by the malignancy (Figure 2a-d).
case_images: Endoscopic and computed tomography images of the duodenum showing a hemorrhagic event. (a) Post-bulbar duodenal ulcer with an exposed vessel. (b) Endoscopic hemostat with three hemoclips (SureClip; Micro-Tech Co., Ltd). (c) Thickened wall in the second part of the duodenum with the biliary stent. The presence of a thickened wall with internal heterogeneity was also misleading.
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case_images: Endoscopic hemostasis was performed using the clipping technique (Figure 3a-c).
case_images: Histopathologic findings. (a, b) Storiform fibrosis and obliterative phlebitis observed in the pancreatic parenchyma ([a] hematoxylin and eosin staining, x200; [b] Verhoeff's elastic staining, x200). The number of immunoglobulin G4 (IgG4)-positive plasma cells/high-power field was 100 (not shown). (c) Lymphoplasmacytic infiltration within the muscularis propria, which resembled a "striated inflammatory lesion" ([c] duodenum; hematoxylin and eosin staining, x100). (d) Lymphoplasmacytic infiltration in the mucosal lamina propria ([d] duodenum, IgG4 staining; x200). The number of IgG4-positive cells per high-power field was over 50 and the IgG4/IgG-positive cell ratio was 50% (not shown).
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case_images: AIP (Figure 4a,b). Abundant IgG4-positive cells were also found in the inflamed lesion of the duodenal wall (Figure 4c,d), suggesting IgG4-RD involvement.