Modification of Management Algorithm of Radiologically Suspected Pancreatic and Biliary Malignancy by Incorporation of Local Experience of Autoimmune Pancreatitis

Objectives: To review the clinical and pathological features of autoimmune pancreatitis (AIP) in a tertiary referral centre in Hong Kong, and to determine preoperative factors that facilitate diagnosis of AIP in order to avoid Whipple's procedure. Methods: According to our pathology and radiology databases, 13 patients were diagnosed in our hospital with type 1 AIP from 1 January 2003 to 31 December 2013. Clinical, serological, radiological and histopathological features and treatment outcomes were analysed. Results: The mean age of patients was 63.2 years with a male predominance (85%). Obstructive jaundice was the most common presenting symptom (69%). Serum immunoglobulin G4 (IgG4) was measured in 12 patients and was elevated in all cases. Focal pancreatic mass was the most common radiological manifestation (46%), followed by diffuse (31%) and segmental (23%) swelling of the pancreas. Subgroup analysis of subjects diagnosed only after surgery showed significant elevation of postoperative serum IgG4 level, with extrapancreatic manifestations present in two cases. Conclusions: In this cohort, our AIP patients showed similar features with those in China and Taiwan, but different to those in Japan and Korea. A future large-scale multicentre cohort would help determine whether AIP manifests differently in different geographical locations. AIP can mimic pancreatic and biliary malignancies, thus radiologists should be familiar with its typical radiological features. Serum IgG4 should be measured and extrapancreatic manifestations looked for in patients who manifest with radiologically suspected pancreatic cancer or extrahepatic cholangiocarcinoma at the pancreatic level. Judicious use of endoscopic ultrasound-guided biopsy, endoscopic retrograde pancreatography, and steroid trial in selected cases would be valuable to exclude malignancy and confirm AIP. Some Whipple's procedures can hopefully be avoided by these measures.