2023 ARRS ANNUAL MEETING - ABSTRACTS

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E1139. Spotlight on Rare Entity: Imaging Features of IgG4-Related Pancreatic Head Pseudotumors
Authors
  1. Faheemullah Khan; Aga Khan University Hospital
  2. Jehanzeb Shahid; Aga Khan University Hospital
  3. Uffan Zafar; Aga Khan University Hospital
  4. Noman Khan; Aga Khan University Hospital
  5. Muhammad Azeemuddin; Aga Khan University Hospital
  6. Tanveer Haq; Aga Khan University Hospital
Background
Pancreatic pseudotumors are pancreatic manifestation of a rare systemic autoimmune disease known as IgG4-related sclerosing disease. Presence of hypergammaglobulinemia reflects why it is also called autoimmune pancreatitis. The mean age of presentation is 40–60 years old. They have been referred to as nonneoplastic space occupying lesion in literature, the reason why they mimic pancreatic carcinoma. Patients commonly present with abdominal pain, anorexia and jaundice. Jaundice results from direct involvement of the bile duct by the fibroinflammatory process and occurs in about 75–80% of the patients. The entity has an association with other autoimmune conditions i.e Sjögren's syndrome, lymphocytic thyroiditis and ulcerative colitis. Pancreatic pseudotumor responds well to glucocorticoid therapy differentiating it from pancreatic carcinoma which requires surgical intervention and adjuvant chemotherapy.

Educational Goals / Teaching Points
To introduce readers with the rare form of pancreatitis/pseudotumor, describe imaging findings of autoimmune pancreatitis/pseudotumor mimicking pancreatic cancer, and present a diagnostic algorithm in equivocal cases.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Pancreatic pseudotumor may involve any part of the pancreas; the head is the most common site of pathology. Histology reveal an intense inflammatory cell infiltration around medium-sized and large interlobular ducts. Imaging has an important role in diagnosing this entity. Pancreas may appear diffusely swollen and hypoechoic, referred to as ‘sausage-like. On cross sectional imaging pancreatic pseudotumors appear as diffusely or segmentally enlarged pancreas with obliteration or stenosis of the main pancreatic duct. When present in head region it also affects the bile duct. On computed tomography (CT) they may appear hypoattenuated to isoattenuated and may show calcification reflecting their chronic nature. Being hypermetabolic in nature they behave as pancreatic carcinoma on functional imaging (FDG PET-CT). Pancreatic pseudotumor responds well to glucocorticoid therapy differentiating it from pancreatic carcinoma which requires surgical intervention and adjuvant chemotherapy.

Conclusion
Pancreatic pseudotumor is a rare entity affecting pancreas that often mimic pancreatic carcinoma. Pancreatic pseudotumor is a benign disease with different therapy and prognosis compared to pancreatic carcinoma. Misdiagnosis between these two diseases do occur especially when the inflammatory process is localized thus pushing the patient at risk to surgical intervention. This warrants educational awareness among radiologists to correctly identify the entity.