Background: The co-occurrence of type 1 autoimmune pancreatitis (AIP) and pancreatic tumor (PaT) has been\npreviously reported. Pure AIP cases have favorable prognosis and are primarily treated with steroids, while AIP cases\nwith PaT are associated with poor prognosis where the primary management is pancreatic resection. However, itâ??s a\nchallenge to timely identify the concurrent PaT in AIP because of their similar clinical and radiological manifestations.\nMethods: We retrospectively reviewed the data in two medical centers from January 2010 to April 2019. The inclusion\ncriteria were as follows: 1) completion of abdominal CT imaging before invasive procedures to the pancreas, 2) a final\ndiagnosis of type 1 AIP using the 2011 international consensus diagnostic criteria, 3) follow-up duration of at least one\nmonth unless AIP and PaT were identified simultaneously. The presence of PaT in AIP was made based on histopathological\nconfirmation, and the absence of PaT in AIP was defined as no pathological or radiological evidence of concurrent PaT.\nClinical and radiological characteristics including gender, age, surveillance period, serum IgG4 and Ca-199 levels, biopsy,\nextrapancreatic involvement, CT and MR (if performed) imaging characteristics were compared between AIP with and\nwithout PaT. The Fisherâ??s exact test was used for qualitative variables, and nonparametric Mann-Whitney test for quantitative\nvariables. A p value Less than equal to 0.05 was considered statistically significant.\nResults: A total of 74 patients with type 1 AIP were included, of which 5 (6.7%) had the concurrent PaT. The subtypes were\npancreatic ductal adenocarcinoma (3/5), solitary extramedullary plasmacytoma in the pancreas (1/5) and\ncholangiocarcinoma in the pancreatic segment (1/5), respectively. Gender (p = 0.044), the pattern of pancreatic enlargement\n(p = 0.003), heterogeneity (p = 0.015), low-density (p = 0.004) on CT and rim enhancement on MRI (p = 0.050) differed\nsignificantly between AIP with and without PaT. None of the low-density characteristics on CT or other assessed MRI\ncharacteristics could significantly differentiate the two groups (p>0.05).\nConclusions: Female, focal pancreatic enlargement, pancreatic heterogeneity, low-density on CT and rim enhancement on\nMRI are suggestive of the concurrent PaT in type 1 AIP. The characteristics of low-density on CT or other MRI characteristics\ndid not provide further diagnostic values.
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