Pancreatic tumor in type 1 autoimmune pancreatitis: a diagnostic challenge

Abstract

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

European Guideline on IgG4‐related digestive disease – UEG and SGF evidence‐based recommendations

“…Comments: Diagnosis of AIP is not always straightforward and, in some cases, it is not easy to differentiate it from pancreatic cancer. Furthermore, an incidence of concomitant pancreatic tumours (benign and malign) in patients with AIP has been reported in up to 7% of cases 47 . The International Study Group of Pancreatic Surgery consensus statement reported that 5–13% of patients undergoing surgical resections because of suspected malignancy had benign findings on pathology, with AIP accounting for 30–43% of these findings 48 .…”

“…Furthermore, an incidence of concomitant pancreatic tumours (benign and malign) in patients with AIP has been reported in up to 7% of cases. 47 The International Study Group of Pancreatic Surgery consensus statement reported that 5-13% of patients undergoing surgical resections because of suspected malignancy had benign findings on pathology, with AIP accounting for 30-43% of these findings. 48 In a retrospective study, including pathological analysis of 274 patients who underwent pancreaticoduodenectomy because of presumed malignancy, the prevalence of benign disease was 8.4%, and overall prevalence of AIP was 2.6%.…”

Prevalence of histological features resembling autoimmune pancreatitis in neoplastic pancreas resections

“…Different clinical and radiological modalities, including serum IgG4, CA19‐9, tumour‐specific antigens, gene expression, endoscopic ultrasonography, computerised tomography (CT) and magnetic resonance imaging (MRI), have been explored for differentiating AIP from pancreatic cancer. Radiological studies can be suggestive, but not diagnostic 5,21,22 . Serum IgG4 levels above twice the upper limit of normal are often seen in type 1 AIP, but the sensitivity is not perfect 23–26 .…”

Is autoimmune pancreatitis a risk factor for pancreatic adenocarcinoma?

“…It's in no doubt that focal pancreatic enlargement, low density on CT, female gender, and rim enhancement on MRI in patients with AIP type 1 are suggestive of pancreatic cancer in these patients (18).…”

“…Ikeura et al(17), also in his review article, summarizes the incidence risk of pancreatic cancer in AIP patients at between 0 % and 4.8%. Pancreatic cancer occurs in the vast majority of people with type 1 AIP(8,18).AIP is a clinical manifestation of a group of diseases called IgG4-RD. In this context, the question arose whether IgG4-RD were associated with the induction of the process of carcinogenesis.…”