Title-autoimmune pancreatitis in pancreatic resections done for presumed pancreatic malignancies-An experience of tertiary centre from North India

Background: Autoimmune pancreatitis (AIP) can present as pancreatic mass mimicking malignancy. However, it has specific histomorphology and immunohistology which in clinical context can be diagnostic. Aim: To retrospectively analyze pancreatic resections done for pancreatic head masses to identify cases of autoimmune pancreatitis. Methods: Hematoxylin and eosin stained slides of pancreatic resections (n-142) done for pancreatic masses (2004-2012) were reviewed. Immunohistochemistry for IgG4 was done in cases suggestive of AIP. As controls, 30 pancreatic carcinomas (n-30) and plasma cells rich chronic pancreatitis (n25) were stained with IgG4. Clinical records were retrieved. Results: There were 5/142 cases (3.5%) of autoimmune pancreatitis among pancreatic resections done for presumed pancreatic tumors. There were 3 females and 2 males and age range was 35-65 (mean 51). Presenting symptoms were painless jaundice (n-4), with adult onset diabetes (n-1) and feature of gastric outlet obstruction (n-1). Histomorphology of all the five masses was of Type I autoimmune pancreatitis showing lobulocentric plasma cell rich inflammation and storiform fibrosis. IgG4 positive plasma cells (>10 per high power field) in all the cases diagnosed as autoimmune pancreatitis; though few IgG4 positive plasma cells were positive in controls. Venulitis and veno-oblitrative changes, neural hyperplasia, neuritis were present in all. Serum IgG4 levels done immediately after surgeries in three patients were elevated. Conclusion: Incidence of autoimmune pancreatitis in pancreatic resections done for pancreatic masses is 3.5%. All the five cases were of Type 1 autoimmune pancreatitis with significant number of IgG4 positive plasma cells using >10 positive cells per high power field as cut off.