Focal autoimmune pancreatitis mimicking pancreatic head carcinoma
Obstructive jaundice. Ultrasonography revealed a bulky pancreatic head.
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Axial arterial, coronal and sagittal portal venous CT pancreas reveal focal enlargement of the head of pancreas with loss of the normal peripheral lobulation. No significant differential enhancement compared with the rest of the pancreatic parenchyma . Uncinate process is rounded. Body and tail of the pancreas are of normal appearance.
Borderline dilatation of the main pancreatic duct in the body and tail. Dilated CBD with mildly enhancing wall, with abrupt cut-off at the superior margin of the head of pancreas; mild intrahepatic duct dilatation also present. Peripancreatic fat plane is preserved. Borderline-enlarged/prominent peripancreatic and mesenteric lymph nodes. Mild oedema of the mesenteric fat.
- No significant differential enhancement of the head cf. body and tail
- Mild CBD dilatation with lack of upstream main pancreatic duct dilatation
- No distal pancreatic atrophy
- No infiltration, or encasement, of peripancreatic fat, vessels, etc.
- No convincing metastases
Abrupt narrowing of the CBD with wall thickening and enlarged peripancreatic lymph nodes raised suspicion of malignancy, although here, lymph node enhancement was much more intense than that seen in carcinoma.
Ampullary biopsy performed.
Immunohistochemistry highlighted a mixture of CD3- and CD20-positive T and B lymphocytes and numerous CD138- and IgG-positive plasma cells (150/hpf).
IgG4 was positive in scattered plasma cells (8/hpf).
IgG4/IgG ratio was 0.05.
The patient was started on steroids and the bilirubin level returned to normal.
The follow-up CT 6 months later showed near-total resolution of the apparent mass and resolution of the biliary dilatation.