A sausage-shaped pancreas with a low-attenuation capsule-like rim and loss of clefts, a duct narrowed without upstream dilatation, and other IgG4 organs involved — the mimic of pancreatic cancer that must not be resected.
Orient first
- Type 1 AIP is the pancreatic manifestation of IgG4-related disease; type 2 is associated with inflammatory bowel disease.
- Diffuse form: enlarged, featureless pancreas with a peripheral halo; focal form: a mass mimicking adenocarcinoma.
- The HISORt / ICDC criteria combine imaging, serology, other organ involvement, histology and steroid response (verify the version).
Acquire the study
- Pancreatic (late arterial) and portal venous phases, 1 mm with coronal reformats.
The manoeuvre
- Pancreas: diffuse enlargement with loss of lobulation; a low-attenuation peripheral rim (halo).
- Delayed enhancement of the gland on the portal venous and delayed phases.
- Main duct: long or multifocal narrowing without marked upstream dilatation (> 5 mm raises concern for cancer — verify).
- Other organs: bile duct wall thickening, bilateral renal cortical low-attenuation lesions, retroperitoneal fibrosis.
What confirms it
- Typical diffuse imaging with raised IgG4 or other organ involvement, and response to steroids.
What licenses you to exclude it
- A focal mass with an abruptly cut-off, dilated duct and vascular encasement should be treated as adenocarcinoma until proven otherwise.
The classic misread
- Resecting a focal AIP as adenocarcinoma — look for the duct-penetrating sign and other IgG4 organs.