Idiopathic Duct Centric Pancreatitis (Autoimmune Type 2)

Definition

Mass forming infiltrate of lymphocytes and plasma cells with neutrophilic destruction of ducts

Autoimmune pancreatitis has recently been split into two types
- Lymphoplasmacytic sclerosing pancreatitis (autoimmune type 1)
- Idiopathic duct centric pancreatitis (covered here)
  - Neutrophilic infiltration and destruction of ducts in addition to lymphoplasmacytic infiltrate

Dense periductal infiltrate
- Centered on medium sized pancreatic ducts and intrapancreatic common bile duct
- Predominantly lymphoplasmacytic
  - Predominantly T cells
  - Plasma cells polyclonal
  - May include eosinophils and germinal centers
- Neutrophils infiltrate ulcerate and destroy ductal epithelium
  - Termed "granulocytic epithelial lesions" (GEL)
- Lobules variably involved
  - Predominantly lymphocytes and plasma cells but may include neutrophils
    - May form neutrophilic abcesses
Moderate fibrosis centered on ducts
- Less prominent than in lymphoplasmacytic sclerosing pancreatitis
No obliterative venulitis or arteritis
- Non-obliterative venulitis may be seen
No increase in IgG4 expression
- Immunoperoxidase staining reveals only rare IgG4 positive plasma cells
- Serum elevation of IgG4 is rare
May form a mass (80%), usually in the head, or diffuse enlargement
- Frequently patchy in distribution
May be associated with inflammatory bowel disease
- Extra-pancreatic involvement by lymphoplasmacytic sclerosing lesions not seen
Not associated with:
- Duct dilation
- Lithiasis
- Pseudocyst formation

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 1/19/08, 12/31/08, 1/20/09, 10/31/10, 2/16/11