TABLE 5.

Features to consider when attempting to differentiate autoimmune pancreatitis (AIP) from pancreatic cancer

Feature	Clue
Epidemiology	AIP is rare, less common than pancreatic cancer
Diagnostic criteria	Use the Mayo and other diagnostic criteria mentioned earlier to help diagnose AIP and differentiate it from malignant disease
Serology	Serum IgG4 levels are elevated in 5% of healthy individuals, 10% of those with pancreatic cancer, and 6% of those with chronic pancreatitis; an increased IgG4 level is therefore not specific for AIP. Conversely, elevated serum IgG4 levels can decrease in patients with pancreatic cancer inappropriately treated with corticosteroids
Trial of steroid therapy	All focal pancreatic masses should be sampled before initiation of corticosteroids. Before initiating corticosteroids, a clinical parameter (ie, symptomatology, serology, radiology) must be identified to monitor an objective response during treatment. Corticosteroids often cause subjective improvement in symptoms even in patients without AIP. Corticosteroid response in AIP is generally seen within 2–4 weeks. If no objective response is documented within 4 weeks, the diagnosis is unlikely to be AIP

Adapted from reference 33. Ig Immunoglobulin