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Investigation | Focal AIP | Pancreatic cancer |
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Dual phase CT | Decreased enhancement in pancreatic phase, normal or delayed enhancement in hepatic phase. Enhanced duct sign | Decreased enhancement in pancreatic phase, decreased or minimal increase in enhancement in hepatic phase. |
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MRI | Speckled appearance within hypointense lesion. | Target-like lesion with upstream dilatation of MPD. |
Low diffusion coefficient on DW-MRI | High diffusion coefficient on DW-MRI. |
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18FDG-PET CT | Diffuse FDG uptake | Focal FDG uptake. |
Uptake in salivary gland and kidney |
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ERP/pancreatography | Long segment narrowing of MPD > 3 cm, skip lesions, upstream dilatation of MPD < 5 mm, side branch dilatation from narrowed MPD. | Complete MPD obstruction, short segment narrowing <3 cm, upstream dilatation of MPD > 5 mm. |
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ERC/cholangiography | Lower bile duct stenosis smooth margins, gradual and symmetric narrowing, and fully visible lumen or hourglass appearance. | Short segment stenosis irregular margins, complete obstruction. |
Intrahepatic biliary stricture. |
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EUS | Hyperechoic spots in a hypoechoic mass and the duct-penetrating sign. | Hypoechoic mass with inhomogeneous pattern. Low contrast uptake index on CHE-EUS. |
Delayed enhancement in CHE-EUS. |
Increased thickness of CBD with “sandwich pattern” |
Peripancreatic lymphadenopathy |
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EUS elastography | Strain ratio <4, hue histogram value <175 | High strain ratio >18, hue histogram value >175. |
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EUS-FNA, EUS-TCB | High stromal cellularity with lymphoplasmacytic infiltrates. | Features of carcinoma. |
High immunochemical staining with IgG4. |
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