Pancreatic Pathology Online
Lymphoplasmacytic Sclerosing Pancreatitis (Autoimmune Pancreatitis)
Dr Sampurna Roy MD July 2016
Microscopic image of Autoimmune Pancreatitis. Inflammation is often associated with sclerosis and expansion of periductal tissue.
Autoimmune pancreatitis is a new clinical entity that is characterized by peculiar histopathologic and laboratory findings and by a dramatic clinical response to corticosteroid therapy.
It has been designated variably as lymphoplasmacytic sclerosing pancreatitis, duct-destructive (duct-centric) pancreatitis or autoimmune pancreatitis.
This clinically and pathologically distinct form of chronic pancreatitis is now widely recognized and is considered an autoimmune process.
In about 15% to 20% of patients, autoimmune conditions are present at the time of diagnosis, and in many others, discovered subsequently. The usual "lymphoplasmacytic sclerotic" type tends to be associated with Sjogren, whereas the "granulocytic" subset, with inflammatory bowel disease.
Most patients present with a pancreatic head mass, often with an accompanying stricture of the distal common bile duct, which thus radiologically resembles "pancreas cancer."
This entity accounts for more than a third of the cases of pseudotumoral pancreatitis (mass-forming inflammatory lesions that resemble carcinoma).
The mean age of the patients with this condition is in the mid-50s.
The subset with granulocytic intraepithelial lesions seem to be younger (mid 40s).
Despite the autoimmune association, males are affected as commonly as females.
Histologically, it is characterized by lymphoplasmacytic inflammation with abundant IgG4-positive plasma cells that exhibit an affinity for ducts as well as venules ("peri-venulitis," with or without frank vasculitis).
Diagram of Autoimmune pancreatitis
Inflammation is often associated with sclerosis and expansion of periductal tissue.
In some cases, fibroblastic activity is prominent and resembles "inflammatory pseudotumor" or is even misdiagnosed as "inflammatory myofibroblastic tumor."
In what appears to be a distinct subset of this entity, intraepithelial granulocytic infiltrates may be seen.
Well-developed examples are readily recognized; however, lesser ones may be difficult to distinguish from other forms of pancreatitis based on morphology alone.
Elevated serum IgG4 levels are characteristic and may be very helpful in the differential diagnosis from tumours and tumor-like lesions of the pancreas which seldom result in levels above 135 mg/dL.
Radiologic findings of autoimmune pancreatitis include:
(a) diffuse pancreas enlargement,
(b) multifocal narrowing of the main pancreatic duct,
(c) narrowing of peripancreatic veins, and
(d) tapered narrowing of the distal common bile duct with frequent contrast enhancement.
These findings were usually reversible with steroid therapy.
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