Retrospective comparison between preoperative diagnosis by International Consensus Diagnostic Criteria and histological diagnosis in patients with focal autoimmune pancreatitis who underwent surgery with suspicion of cancer.

OBJECTIVE: The objective of this study was to compare the preoperative diagnosis by International Consensus Diagnostic Criteria (ICDC) with histological diagnosis in patients with focal autoimmune pancreatitis (AIP) who underwent surgery.
METHODS: Thirty patients (type 1 AIP in 23 and type 2 AIP in 7) with a diagnosis of AIP based on histology of surgical specimens were classified according to ICDC based on their preoperative data.
RESULTS: Pancreatic core biopsies and diagnostic steroid trial were not preoperatively performed in any of the patients. Based on preoperative data, ICDC diagnosed 6 patients (20%) as having type 1 AIP and 24 (80%) as probable AIP. Assuming all patients had responded to a steroid trial preoperatively, ICDC would have diagnosed 8 patients (27%) as having type 1 AIP, 4 (13%) as type 2 AIP, 10 as AIP-not otherwise specified (33%), and 8 (27%) as probable AIP. In the hypothetical situation, 7 of 8 type 1 AIP patients and 3 of 3 type 2 AIP patients would have been classified into the correct subtype of AIP.
CONCLUSIONS: A steroid trial enhances the possibility of correctly diagnosing AIP by ICDC despite the lack of histology. However, some patients cannot be diagnosed as having AIP or be classified into the correct subtype without histology.