Pancreas

• No specific radiologic features to distinguish type 2 from type 1
• Contrast enhanced ultrasound (Endosc Ultrasound 2018;7:196):
  • Noninvasive imaging study; dynamic contrast enhancement improved discrimination between autoimmune pancreatitis and pancreatic ductal adenocarcinoma
  • Shows iso or hyperenhancement during the arterial and phases
• CT (AJR Am J Roentgenol 2015;205:2):
  • Important imaging modality for differentiation from pancreatic cancer
  • Diffuse parenchymal involvement, sausage shaped
  • Delayed enhancement studies
  • Rim-like enhancement
• Magnetic resonance (Pancreas 2018;47:1115, Radiology 2011;260:428)
  • T1 weighted: hypointense
  • T2: predominantly hyperintense
  • Dynamic study shows the effect of fibrosis widening the extracellular and extravascular spaces, resulting in hypointensity during pancreatic phase and contrast retention / hyperintensity during the delayed phase
• Magnetic resonance cholangiopancreatography (Pancreas 2018;47:1115)
  • Stenosis of the main pancreatic duct, however with less upstream dilatation than seen in type 1 autoimmune pancreatitis
  • Rare / absent common bile duct stenosis and rare / absent stenosis of intrahepatic bile ducts, consistent with no extra pancreatic organ involvement in type 2 autoimmune pancreatitis compared to type 1 autoimmune pancreatitis

Images hosted on other servers:

• 9 year old girl with intrahepatic and extrahepatic biliary ductal dilatation (Clin J Gastroenterol 2015;8:421)
• 20 year old man with Crohn's disease (Intern Med. 2018 Oct 15;57(20):2957)
• 64 year old man with inflammatory bowel disease and dilated common bile duct (J Investig Med High Impact Case Rep 2017;5:2324709617734245)

• Confined to pancreas
• Key histologic features:
  • Lymphoplasmacytic inflammation, predominantly periductal, although acini are also involved
  • Epithelium of medium and small sized duct walls infiltrated by neutrophils [(granulocytic epithelial lesion(s)] with or without granulocytic acinar inflammation
    • Often causes destruction of the pancreatic duct epithelium
• Lobular fibrosis (but not storiform) and obliterative phlebitis, however less prominent than in type 1 autoimmune pancreatitis
• Absent or scant IgG4 positive cells (plasma cells) (0 - 10 cells / high powered fields) (Gastroenterology 2015;149:39)

Contributed by David J. Escobar, M.D., Ph.D.

A 40 year old man presented with jaundice and abdominal imaging showed a pancreatic mass. Serum IgG4 levels were not elevated. Endoscopic ultrasound guided fine needle biopsy was performed and a representative photomicrograph is shown. Which of the following statements is true?

1. Although serum IgG4 levels are not elevated, will have IgG4 positive cells
2. Despite steroid therapy, the patient's symptoms will persist and this will support the most likely diagnosis
3. Histopathologic findings in the photomicrograph are required for definitive diagnosis
4. Most likely diagnosis is associated with systemic inflammation, with frequent involvement of extra pancreatic organs

C. According to the International Consensus Diagnostic Criteria established in 2011, the definitive diagnosis autoimmune pancreatitis type 2 requires tissue biopsy of the pancreas demonstrating granulocytic infiltration of the pancreatic duct wall [(granulocytic epithelial lesion(s)].
Answer choice A: IgG4 positive cells are absent in autoimmune pancreatitis type 2. This finding is more characteristic of autoimmune pancreatitis type 1.
Answer choice B: Both autoimmune pancreatitis types 1 and 2 respond to the steroid therapy.
Answer choice D: Autoimmune pancreatitis type 2 is not associated with extra pancreatic organ manifestations. This finding is more characteristic of autoimmune pancreatitis type 1.


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Reference: Autoimmune pancreatitis type 2

A 45 year old woman presented with abdominal pain and jaundice. Abdominal imaging showed a diffusely enlarged sausage shaped pancreas and stenosis of the main pancreatic duct. Serum amylase, lipase and IgG4 levels were not elevated. During the workup, endoscopic ultrasound guided fine needle biopsy was performed and histologic sections showed pancreatic duct centric inflammation including ductal epithelium with intra-epithelial neutrophils. Upon further gathering of past medical history, the patient was most likely found to have which of the following?

1. Ankylosing spondylitis
2. Inflammatory bowel disease
3. Salivary gland enlargement and thyroiditis
4. Systemic lupus erythematosus

B. There is a known association between autoimmune pancreatitis type 2 and inflammatory bowel disease, especially ulcerative colitis, occurring in 15 - 20% of biopsy proven autoimmune pancreatitis type 2. The basis of this association is unclear.
Answer choice A: Ankylosing spondylitis is an inflammatory disease that is associated with HLA-B27 and is not known to be associated with autoimmune pancreatitis type 2.
Answer choice C: Autoimmune pancreatitis type 1 is an IgG4 related disease. Patients often present with extra pancreatic manifestations of systemic IgG4 related inflammation including enlarged salivary glands and Riedel thyroiditis or the sclerosing variant of Hashimoto thyroiditis.
Answer choice D: Systemic lupus erythematosus is not known to be associated with autoimmune pancreatitis type 2.


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Reference: Autoimmune pancreatitis type 2