IgG4-related autoimmune pancreatitis mimicking pancreatic carcinoma: a case report

A 59-year-old woman presented with a 5-month history of an incidentally discovered pancreatic mass and episodic epigastric pain. Imaging studies revealed a mass in the pancreatic head, neck and tail with suspected vascular encasement and markedly elevated tumor marker CA19-9. Based on these findings, pancreatic malignancy was initially suspected. However, serum IgG4 was extremely elevated at 10,022 μg/mL and ultrasound-guided pancreatic biopsy showed benign ductal epithelium without adenocarcinoma. A diagnosis of IgG4-related autoimmune pancreatitis was established. The patient was treated with oral methylprednisolone at 32 mg daily and pancreatic enzyme supplements. During one year of follow-up, serum IgG4 normalized to 489 μg/mL, CA19-9 returned to 16 U/mL, and serial MRI examinations demonstrated marked improvement of the pancreatic head and neck mass and biliary stricture.