- No history of alcohol use or biliary stone disease
- Immune-mediated
- Gland infiltrated by CD4 positive lymphocytes and plasma cells
- Serum IgG4 sometimes elevated
- Responds to steroids
- Focal form difficult to distinguish from malignancy
- May be associated with other IgG4 issues: cholangitis, renal, salivary gland or lacrimal gland inflammation, lymphadenopathy
Imaging
- 3 types in imaging: diffuse, focal or multi-focal
- Diffuse most common 70%
- Diffuse (sausage shaped) or focal gland enlargement
- Minimal duct dilatation
- Delayed contrast enhancement
- Perpancreatic hypo-attenuating rim