Lymphoplasmacytic Sclerosing Pancreatitis (Autoimmune Type 1)

Definition

Autoimmune pancreatitis has recently been split into two types
- Lymphoplasmacytic sclerosing pancreatitis (covered here)
- Idiopathic duct centric pancreatitis (autoimmune type 2)
  - 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
  - Ductal epithelium preserved
- Predominantly lymphoplasmacytic
  - Predominantly T cells
  - Plasma cells polyclonal
  - May include eosinophils and germinal centers
  - Neutrophils are rare
- Lobules frequently involved
  - Results in lobular atrophy
- Infiltrate can extend into peripancreatic fat
Storiform, swirling fibrosis centered on ducts
- May have onion-skin pattern
- Frequently causes duct stenosis
Frequent obliterative venulitis
- Lymphoplasmacytic infiltrate in vein walls
- Frequent lumenal obliteration
- Infrequent arteritis
Increased IgG4 expression
- Immunoperoxidase staining with >30 IgG4 positive plasma cells / HPF is strongly suggestive of the diagnosis
  - Some use a cutoff of >10
- Serum elevation of IgG4 is suggestive of the diagnosis
  - Occasional elevations with other disorders
- Increased IgG4 positive plasma cells in ampullary biopsies has been reported (Sepehr)
  - Proposed as a diagnostic aid
May form a mass (80%), usually in the head, or diffuse enlargement
- Frequently patchy in distribution
Extra-pancreatic involvement frequently present (see Clinical at left sidebar)
- Histologically similar lesions
Not associated with:
- Duct dilation
- Lithiasis
- Pseudocyst formation

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