Type 1 Autoimmune Pancreatitis Suspected with Marked Changes and Difficulty in Diagnosis

Abstract

A 71-year-old woman visited a general practitioner on account of low back pain. Abdominal ultrasound showed a tumor in the head of the pancreas. She was referred to our department for examination. CT on admission revealed a 50-mm-diameter tumor, which was slightly enhanced at the margin of the head of the pancreas. However, CT performed 5 days after admission showed that the tumor had decreased to 25 mm in diameter, and endoscopic ultrasound (EUS) showed the tumor as a low-echoic cystic lesion. ERCP showed a stricture of the lower bile duct. No malignant cells were observed in the pancreatic juice and bile or on biopsy of the duodenal ulcer close to the papilla. Finally, needle biopsies of the pancreas using laparotomy were performed. According to the histological findings, the patient was diagnosed with type 1 autoimmune pancreatitis.