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Pancreas

Pancreatitis

Autoimmune pancreatitis


Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 23 November 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Chronic inflammatory disease of pancreas
● Also called primary sclerosing cholangitis-like pancreatitis, non-alcoholic duct destructive chronic pancreatitis (Arch Pathol Lab Med 2000;124:1535)
● Forms mass that may constrict bile duct with dense periductal inflammatory infiltrate, and clinically is thought to be malignant
● Has 2 subtypes (Am J Surg Pathol 2011;35:26, Semin Diagn Pathol 2012;29:197)

Type 1 / lymphoplasmacytic sclerosing pancreatitis

● Pancreatic manifestation of IgG4 related systemic disease (BMC Med 2006;4:23)
● Pancreas shows hypercellular lymphoplasmacytic infiltrate of interlobular stroma (91%), storiform type fibrosis, >10 IgG4 plasma cells / high-power field (typically >50/HPF), infiltrate may extent to peripancreatic tissue
● 75% male, older patients, often presents with jaundice; may recur within and outside pancreas
● Associated with sclerosing cholangitis, Sjögren-like syndrome, obliterative phlebitis, arterial involvement

Type 2 / idiopathic duct centric pancreatitis

● Confined to pancreas (i.e. not systemic)
● Pancreas shows microabscesses and ductal ulceration (78%), granulocyte epithelial lesions, only occasional IgG4 plasma cells (<10/HPF)
● Often pancreatic tail cut-off sign by imaging (40%), disease recurrence uncommon
● No gender preference, younger patients, associated with inflammatory bowel disease, not with obliterative phlebitis
● By definition, no known cause for chronic pancreatitis (i.e. no alcohol abuse), and features of classic chronic pancreatitis (fat necrosis, pseudocysts, calcifications, dilated ducts with inspissated secretions) are absent
● Compared to chronic pancreatitis NOS, more foci of periductal inflammation and neutrophilic microabscesses

Treatment
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● Steroids (Front Physiol 2012;3:374)
● Overall prognosis is excellent

Gross description
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● Pancreatic mass with regional nodal swelling
● Narrowing of main pancreatic duct

Micro description
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Type 1:
● Prominent periductal and acinar lymphoplasmacytic infiltration and fibrosis around the pancreatic ducts
● Marked acinar atrophy, phlebitis of pancreatic and portal veins
● >10 IgG4 plasma cells / high-power field, infiltrate may extent to peripancreatic tissue

Type 2:
● Microabscesses and ductal ulceration (78%), no IgG4 plasma cells
● No calcifications, no fat necrosis, no cyst formation

Micro images
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Type 1 cases


Type 2: small caliber ducts with granulocytic epithelial lesions


Type 1 and type 2 cases

Cytology images
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Left: type 1; right: type 2 cases

Differential diagnosis
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Chronic pancreatitis: often history of alcohol abuse; pancreas exhibits fat necrosis, pseudocysts, calcifications, dilated ducts with inspissated secretions; usually less periductal inflammation and neutrophilic microabscesses
Pancreatic adenocarcinoma: marked atypia and invasion is present, may have IgG4+ plasma cells (J Gastroenterol 2012 Oct 5 [Epub ahead of print])

End of Pancreas > Pancreatitis > Autoimmune pancreatitis


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