Gupta R, et al. - Researchers examined the diagnostic utility of PD-L1 and indoleamine 2,3-dioxygenase (IDO1) expression in distinguishing type 2 autoimmune pancreatitis (AIP) from other forms of pancreatitis and pancreatic ductal adenocarcinoma (PDAC) via evaluating 35 pancreatectomy specimens diagnosed with type 2 AIP and potential mimics of this disease including type 1 AIP (n=14), chronic pancreatitis-not otherwise specified (n=10), groove pancreatitis (n=14), and PDAC (n=278). Patients with type 2 AIP had the mean age of 50 years with a F:M ratio of 1.2:1. For PD-L1 and IDO1, pancreatic ductal staining was noted in 69% (24/35) and 60% (15/25) of cases with type 2 AIP, respectively. PD-L1 as a marker of type 2 AIP exhibited the sensitivity and specificity of 70% and 99%, respectively. These findings suggest the potential value of ductal PD-L1 reactivity to distinguish type 2 AIP from other forms of pancreatitis and PDAC.