A 66-year-old man who was on oral medication for type 2 diabetes experienced a rapid decline in glycemic control (increase in glycosylated hemoglobin level from 7.7 to 10.2% over 3 months). Abdominal ultrasonography revealed a 20-mm hypoechoic mass in the pancreatic tail. Serum tumor marker carbohydrate antigen 19–9 and DUPAN2 levels were within the respective normal ranges; serum IgG4 level was also normal at 21.8 mg/dL. Abdominal contrast computed tomography revealed a 26-mm tumor in the pancreatic tail. Magnetic resonance cholangiopancreatography revealed disruption of the main pancreatic duct and dilation of the caudal pancreatic duct. Endoscopic ultrasonography revealed a near-round-shaped hypoechoic mass with interspersed hyperechoic areas. Endoscopic ultrasonography-guided fine needle aspiration was performed using a 22-G needle, but no malignant findings were observed. There were no signs of sialadenitis, retroperitoneal fibrosis, nephropathy, or other conditions associated with IgG4-related diseases. Distal pancreatectomy was performed; a 23-mm white mass was resected from the pancreatic tail. A histopathological examination showed advanced inflammatory cell infiltration mainly involving lymphocytes/plasma cells along with storiform fibrosis and obliterative phlebitis. No more than five IgG4-positive cells were observed per high-power field. These were level 1 pathological findings, and a definitive diagnosis of type 1 autoimmune pancreatitis (AIP) was made according to the International Consensus Diagnostic Criteria. Type 1 AIP associated with normal serum IgG4 levels and absence of IgG4-positive cells on histological examination is a rare clinical entity, which is very difficult to distinguish from pancreatic cancer. Here we report such a case and present a review of the relevant literature.
Autoimmune pancreatitis Pancreatic cancer IgG4
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Compliance with ethical standards
Conflict of interest
Yuichi Takano, Takahiro Kobayashi, Fumitaka Niiya, Eiichi Yamamura, Naotaka Maruoka, Kazuaki Yokomizo, Hiroki Mizukami, Jun-ichi Tanaka2 Tomoko Norose, Nobuyuki Ohike, and Masatsugu Nagahama declare that they have no conflict of interest.
All procedures followed have been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
Informed consent was obtained from all patients for being included in the study.
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