P1145 - Autoimmune Pancreatitis Masquerading as Pancreatic Mass

Pranav Patel, MD¹, Ammara Khalid, MD¹, Yakub I. Khan, MD^2
1Geisinger Medical Center, Danville, PA; ²Geisinger Medical Center, Wilkes-Barre, PA

Introduction: Autoimmune pancreatitis (AIP) occurs in approximately 5-10% of patients diagnosed with chronic pancreatitis. It is twice as common in men as in women and the mean age of diagnosis is 55 years. A combination of criteria including histology, imaging, serology, other organ involvement, and response to steroid therapy (HISORt criteria) can aid in diagnosis of AIP. AIP can present with painless jaundice, diffusely swollen pancreas, abdominal pain or focal mass. We are presenting an interesting case of AIP masquerading as pancreatic tail mass.

Case Description/Methods: 73-year-old male with medical history of diabetes mellites, status post cholecystectomy, former smoker was referred for evaluation of pancreatic tail mass found incidentally on CT chest. Subsequent PET scan revealed increased metabolic activity at pancreatic tail measuring 3cm x 1.9cm concerning for a mass. MRI with gadolinium contrast was consistent with indeterminate pancreatic mass like thickening at the distal pancreatic tail, with delayed phase enhancement suggestive of possible neoplastic process. Endoscopic ultrasound guided fine needle aspiration and biopsy were performed to confirm diagnosis. EUS revealed a mass in the pancreatic tail staged T2N0Mx by endosonographic criteria (Image 1). EUS guided biopsy (EUS-FNB) of pancreatic mass was significant for marked chronic inflammation consisting of lymphoplasmacytic cells predominantly, along with atrophy and fibrosis. Frequent plasma cells noted in which about 40-45% of IgG positive. Cells were positive for IgG4. The overall histological findings were consistent with AIP. There was no pathologic evidence of malignancy. Patient was reassured and started on steroids.

Discussion: AIP can cause chronic inflammation of pancreas with diffuse swelling of pancreas along with abdominal symptoms. It can also present as painless jaundice however in this patient liver chemistry were unremarkable likely due to pancreatic tail area involvement. Rarely, it can also present as focal pancreatic mass that mimics pancreatic malignancy such as this case. EUS-FNB can provide histological diagnosis of AIP described as lymphoplasmacytic sclerosing pancreatitis or >10 IgG4-positive cells with lymphoplasmacytic infiltration and fibrosis. Serum IgG 4 elevation more than 2 times can be suggestive but not specific of AIP. Glucocorticoid treatment gives dramatic response in patients with AIP. Overall a combination of the HISORt criteria can be used to confirm a variety of manifestations of AIP.


Figure: Image 1: Endoscopic ultrasound showing pancreatic mass.


Disclosures:
Pranav Patel indicated no relevant financial relationships.
Ammara Khalid indicated no relevant financial relationships.
Yakub Khan indicated no relevant financial relationships.


Pranav Patel, MD¹, Ammara Khalid, MD¹, Yakub I. Khan, MD². P1145 - Autoimmune Pancreatitis Masquerading as Pancreatic Mass, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.