Autoimmune pancreatocholangitis, non-autoimmune pancreatitis and primary sclerosing cholangitis: a comparative morphological and immunological analysis

A Diagnostic Challenge: Pancreatic Cancer or Autoimmune Pancreatitis?

ABSTRACT: We report a rare case of seronegative autoimmune pancreatitis (AIP) that presented as a pancreatic focal lesion and was considered to be pancreatic cancer based on the clinical presentation and imaging findings. The endoscopic ultrasound-guided biopsies of the pancreatic mass revealed no malignant cells and the pancreatic swelling had become diffuse on repeat imaging. AIP was suspected and a trial of steroids was considered as a diagnostic and therapeutic method. The patient responded dramatically to corticosteroid treatment with resolution of symptoms and normal imagining and laboratory parameters. This case highlights the challenge in the diagnostic approach of a pancreatic mass.

Stromal heterogeneity in pancreatic cancer and chronic pancreatitis

BACKGROUND/OBJECTIVES

An abundant stromal reaction is a hallmark of pancreatic ductal adenocarcinoma (PDAC) and chronic pancreatitis (CP). The cells mainly responsible for the stromal reaction are activated pancreatic stellate cells (PSCs). Despite their crucial role, PSCs are not well characterized. PSCs share characteristics with the better-known hepatic stellate cells (HSCs). The aim of this study was a detailed analysis of PSCs in PDAC and CP.

METHODS

Whole-slide specimens of CP (n = 12) and PDAC (n = 10) were studied by histochemistry and immunohistochemistry. The stroma was evaluated using Movat's pentachrome stain. PSCs were tested by immunohistochemistry for PSC markers (α-SMA, CD34, desmin, NGFR, SPARC and tenascin C) and HSC markers (α-crystallin B, CD56, NGF, NT-3, synaptophysin and TrkC). Alpha-SMA, tenascin C, SPARC and NT-3 staining were verified on tissue micro arrays (TMAs) from a well-characterized cohort of 223 PDAC patients. PSCs isolated from human PDAC and CP tissue samples as well as HSCs were evaluated by immunofluorescence.

RESULTS

While the stroma of CP cases was characterized by a collagen-rich fibrosis, PDAC stroma displayed higher mucin content (p = 0.0002). PSCs showed variable expression of tested markers. In PDAC samples, staining of most markers was found around tumor complexes, while CP samples showed a greater variety of localizations. Alpha-SMA staining correlated with collagen-rich fibrosis (p = 0.012), while NT-3 staining correlated with mucin-rich stroma (p = 0.008). A peritumoral staining was confirmed for α-SMA, tenascin C, SPARC and NT-3 in the PDAC TMA cohort (n = 223). In a subgroup of patients with pancreatic head tumors and UICC 2009 IIB (n = 144), α-SMA staining intensity was a prognostic factor for overall survival at uni- and multivariate analysis (p = 0.036 and p = 0.002).

CONCLUSIONS

The close similarities between PSCs and HSCs were confirmed. Heterogeneous expression patterns of the tested markers might reflect different levels of activation or differentiation, or even multiple subpopulations of PSCs. Survival analysis suggests an impact of stromal composition on survival.

IgG4-related disease: with emphasis on the biopsy diagnosis of autoimmune pancreatitis and sclerosing cholangitis

In 2011, chronic fibroinflammatory processes occurring simultaneously or metachronously in various organs and associated with elevated IgG4 serum levels and/or tissue infiltration with IgG4-positive plasma cells have been recognized as manifestations of a systemic disorder called IgG4-related disease (IgG4-RD). The histologic key findings are lymphoplasmacytic infiltration rich in IgG4-positive plasma cells combined with storiform fibrosis and obliterative phlebitis. Among the organs mainly affected by IgG4-RD are the pancreas and the extrahepatic bile ducts. The pancreatic and biliary alterations have been described under the terms autoimmune pancreatitis (AIP) and sclerosing cholangitis, respectively. These diseases are currently more precisely called IgG4-related pancreatitis (or type 1 AIP to distinguish it from type 2 AIP that is unrelated to IgG4-RD) and IgG4-related sclerosing cholangitis (IgG4-related SC). Clinically and grossly, both diseases commonly imitate pancreatic and biliary adenocarcinoma, tumors that are well known for their dismal prognosis. As IgG4-RD responds to steroid treatment, making a resection of a suspected tumor unnecessary, a biopsy is often required to establish the preoperative diagnosis. This review discusses the morphologic spectrum of IgG4-related pancreatitis and IgG4-related SC and focuses on the biopsy relevant histologic features for the diagnosis and differential diagnosis of these diseases.

Chronic pancreatitis

Chronic pancreatitis is defined as a pathological fibro-inflammatory syndrome of the pancreas in individuals with genetic, environmental and/or other risk factors who develop persistent pathological responses to parenchymal injury or stress. Potential causes can include toxic factors (such as alcohol or smoking), metabolic abnormalities, idiopathic mechanisms, genetics, autoimmune responses and obstructive mechanisms. The pathophysiology of chronic pancreatitis is fairly complex and includes acinar cell injury, acinar stress responses, duct dysfunction, persistent or altered inflammation, and/or neuro-immune crosstalk, but these mechanisms are not completely understood. Chronic pancreatitis is characterized by ongoing inflammation of the pancreas that results in progressive loss of the endocrine and exocrine compartment owing to atrophy and/or replacement with fibrotic tissue. Functional consequences include recurrent or constant abdominal pain, diabetes mellitus (endocrine insufficiency) and maldigestion (exocrine insufficiency). Diagnosing early-stage chronic pancreatitis is challenging as changes are subtle, ill-defined and overlap those of other disorders. Later stages are characterized by variable fibrosis and calcification of the pancreatic parenchyma; dilatation, distortion and stricturing of the pancreatic ducts; pseudocysts; intrapancreatic bile duct stricturing; narrowing of the duodenum; and superior mesenteric, portal and/or splenic vein thrombosis. Treatment options comprise medical, radiological, endoscopic and surgical interventions, but evidence-based approaches are limited. This Primer highlights the major progress that has been made in understanding the pathophysiology, presentation, prevalence and management of chronic pancreatitis and its complications.

Distinct pathophysiological cytokine profiles for discrimination between autoimmune pancreatitis, chronic pancreatitis, and pancreatic ductal adenocarcinoma

BACKGROUND

Discriminating between autoimmune pancreatitis (AIP), chronic pancreatitis (CP), and pancreatic ductal adenocarcinoma (PDAC) can be challenging. In this retrospective study, levels of serum and tissue cytokines were analyzed as part of the clinical strategy for the preoperative differentiation between AIP and PDAC. The identification of differential cytokine profiles may help to prevent unnecessary surgical resection and allow optimal treatment of these pathologies.

METHODS

To compare the cytokine profiles of AIP, CP, and PDAC patients, serum and pancreatic tissue homogenates were subjected to multiplex analysis of 17 inflammatory mediators. In total, serum from 73 patients, composed of 29 AIP (14 AIP-1 and 15 AIP-2), 17 CP, and 27 PDAC, and pancreatic tissue from 36 patients, including 12 AIP (six AIP-1 and six AIP-2), 12 CP, and 12 PDAC, were analyzed.

RESULTS

Comparing AIP and PDAC patients' serum, significantly higher concentrations were found in AIP for interleukins IL-1β, IL-7, IL-13, and granulocyte colony-stimulating factor (G-CSF). G-CSF also allowed discrimination of AIP from CP. Furthermore, once AIP was divided into subtypes, significantly higher serum levels for IL-7 and G-CSF were measured in both subtypes of AIP and in AIP-2 for IL-1β when compared to PDAC. G-CSF and TNF-α were also significantly differentially expressed in tissue homogenates between AIP-2 and PDAC.

CONCLUSIONS

The cytokines IL-1β, IL-7, and G-CSF can be routinely measured in patients' serum, providing an elegant and non-invasive approach for differential diagnosis. G-CSF is a good candidate to supplement the currently known serum markers in predictive tests for AIP and represents a basis for a combined blood test to differentiate AIP and particularly AIP-2 from PDAC, enhancing the possibility of appropriate treatment.

Identification of Novel Serum Autoantibodies for Differential Diagnosis of Autoimmune Pancreatitis and Pancreatic Ductal Adenocarcinoma

OBJECTIVES

The lack of specific biochemical markers is a major drawback for the diagnosis of autoimmune pancreatitis (AIP). The aims were to characterize the autoantibody profiles in AIP and pancreatic ductal adenocarcinoma (PDAC) and to identify circulating autoantibodies that could be diagnostic markers differentiating PDAC and the AIP subtypes.

METHODS

Tissue lysates obtained from the resected pancreas of patients with AIP and patients with PDAC were separated by 2-dimensional polyacrylamide gel electrophoresis subsequently immunoblotted with autologous sera. The immunoreactive spots were subjected to nanoscale liquid chromatography-electrospray ionization tandem mass spectrometry to identify serum autoantibodies to tissue-derived autoantigens associated with AIP and PDAC. Autoantibody concentrations for selected autoantigens were assessed by enzyme-linked immunosorbent assays.

RESULTS

A total of 115 immunoreactive spots were identified by 2-dimensional polyacrylamide gel electrophoresis/immunobloting. Nanoscale liquid chromatography-electrospray ionization tandem mass spectrometry-based analysis revealed 68 autoantigens in AIP, 26 in PDAC, and 21 present in both diseases. Assessment of 13 selected AIP autoantibody serum levels revealed that 7 of them had significantly higher titers in AIP versus PDAC. IgG-directed against transaldolase could significantly differentiate between the 2 AIP subtypes.

CONCLUSIONS

The novel panel of AIP autoantibodies is promising to supplement the predictive tests for AIP of the currently known autoantigens and represent a basis for a combined blood test to differentiate AIP from PDAC in the future.

IgG4-related hepatobiliary disease: an overview

IgG4-related hepatobiliary diseases are part of a multiorgan fibroinflammatory condition termed IgG4-related disease, and include IgG4-related sclerosing cholangitis (IgG4-SC) and IgG4-related hepatopathy. These diseases can present with biliary strictures and/or mass lesions, making them difficult to differentiate from primary sclerosing cholangitis (PSC) or other hepatobiliary malignancies. Diagnosis is based on a combination of clinical, biochemical, radiological and histological findings. However, a gold standard diagnostic test is lacking, warranting the identification of more specific disease markers. Novel assays - such as the serum IgG4:IgG1 ratio and IgG4:IgG RNA ratio (which distinguish IgG4-SC from PSC with high serum IgG4 levels), and plasmablast expansion to recognize IgG4-SC with normal serum IgG4 levels - require further validation. Steroids and other immunosuppressive therapies can lead to clinical and radiological improvement when given in the inflammatory phase of the disease, but evidence for the efficacy of treatment regimens is limited. Progressive fibrosclerotic disease, liver cirrhosis and an increased risk of malignancy are now recognized outcomes. Insights into the genetic and immunological features of the disease have increased over the past decade, with an emphasis on HLAs, T cells, circulating memory B cells and plasmablasts, chemokine-mediated trafficking, as well as the role of the innate immune system.

IgG4-related sclerosing cholangitis: all we need to know

Our knowledge and experience of IgG4-related sclerosing cholangitis (ISC) have expanded in the last decade. ISC is one of the common organ manifestations of IgG4-related disease (IgG4-RD); approximately 60 % of patients with this systemic condition have ISC in the proximal and/or distal bile ducts. ISC needs to be discriminated from primary sclerosing cholangitis, cholangiocarcinoma, and other rare forms of lymphoplasmacytic cholangiopathy (e.g., follicular cholangitis and sclerosing cholangitis with granulocytic epithelial lesions). Its diagnosis requires a multidisciplinary approach, in which serology, histology, and imaging play crucial roles. Treatments with high-dose corticosteroids typically lead to the rapid and consistent induction of disease remission. Another promising therapeutic approach is B-cell depletion with rituximab. Although disease relapse is relatively common, provided that appropriate treatments are administered, ISC is considered a "benign" disease with a low risk of liver failure and biliary malignancy. Its molecular pathology is characterized by Th2-dominant immune reactions, regulatory T-cell activation, and CCL1-CCR8 interactions. Particular subsets of B cells such as plasmablasts and regulatory B cells also expand. A recent global proteomic study demonstrated that three significantly activated immunological cascades in ISC were all B-cell- or immunoglobulin-related (Fc-gamma receptor-mediated phagocytosis, B-cell receptor signaling pathway, and Fc-epsilon receptor I signaling pathway), suggesting the crucial roles of B cells in the underlying immune reactions. Despite the expansion of our knowledge of the pathophysiology of ISC, the exact role of IgG4 remains unclear. A better understanding of its immunopathology will offer some potential drug targets for this emerging biliary disease.

Collagen type V promotes the malignant phenotype of pancreatic ductal adenocarcinoma

Excessive matrix production by pancreatic stellate cells promotes local growth and metastasis of pancreatic ductal adenocarcinoma and provides a barrier for drug delivery. Collagen type V is a fibrillar, regulatory collagen up-regulated in the stroma of different malignant tumors. Here we show that collagen type V is expressed by pancreatic stellate cells in the stroma of pancreatic ductal adenocarcinoma and affects the malignant phenotype of various pancreatic cancer cell lines by promoting adhesion, migration and viability, also after treatment with chemotherapeutic drugs. Pharmacological and antibody-mediated inhibition of β1-integrin signaling abolishes collagen type V-induced effects on pancreatic cancer cells. Ablation of collagen type V secretion of pancreatic stellate cells by siRNA reduces invasion and proliferation of pancreatic cancer cells and tube formation of endothelial cells. Moreover, stable knock-down of collagen type V in pancreatic stellate cells reduces metastasis formation and angiogenesis in an orthotopic mouse model of ductal adenocarcinoma. In conclusion, paracrine loops involving cancer and stromal elements and mediated by collagen type V promote the malignant phenotype of pancreatic ductal adenocarcinoma and underline the relevance of epithelial-stromal interactions in the progression of this aggressive neoplasm.

Diagnosis and treatment of autoimmune pancreatitis types 1 and 2

Background

Autoimmune pancreatitis (AIP) is characterized by diffuse or focal swelling of the pancreas. AIP has been divided into types 1 and 2. The aim of the study was to evaluate and compare the clinicopathological characteristics, therapy and outcome of patients with AIP.

Methods

The medical records of patients diagnosed with AIP between January 2003 and July 2011 were reviewed. Characteristics of patients with AIP types 1 and 2 were compared with those of patients with pancreatic ductal adenocarcinoma (PDAC).

Results

AIP was classified as type 1 in 40 patients and type 2 in 32 according to the HISORt (Histology, Imaging, Serology, Other organ involvement, Response to therapy) criteria. Patients with histologically confirmed AIP type 2 were younger than those with type 1 (P = 0·005). Some 30 of 32 patients with AIP type 2 were found to have a localized tumour-like pancreatic mass and underwent pancreatectomy, compared with only 16 of 40 with type 1 (P < 0·001). Three of 25 patients with AIP type 2 presented with raised serum levels of IgG4 compared with 21 of 38 with type 1 (P < 0·001). There was no difference in symptoms and involvement of other organs between AIP types 1 and 2. Presentation with weight loss was more common among patients with PDAC than those with AIP, but there was no difference in pain or jaundice between the groups. Raised serum carbohydrate antigen 19-9 levels were more prevalent in patients with PDAC.

Conclusion

Patients with AIP type 2 frequently present with abdominal pain and a tumour-like mass. Differentiating AIP from PDAC is difficult, so making the clinical decision regarding operative versus conservative management is challenging.

Frequency and significance of IgG4 immunohistochemical staining in liver explants from patients with primary sclerosing cholangitis

Dense tissue infiltrates of IgG4⁺ plasma cells >50/high-powered field (HPF) are purportedly highly specific for IgG4-related disease. However, the frequency and significance of liver-infiltrating IgG4⁺ plasma cells in primary sclerosing cholangitis (PSC) applying these cut-offs has not been determined. We sought to determine the incidence of intrahepatic IgG4-positive staining in PSC patients undergoing transplantation, correlating findings with clinical parameters. Immunohistochemical staining was performed on liver explants obtained between 1991 and 2009. Of 122 explants obtained, hilar IgG4⁺ staining was found to be mild (10–29 IgG4⁺ cells/HPF) in 23.0%, moderate (30–50/HPF) in 9.0% and marked (>50/HPF) in 15.6%. Marked hilar lymphoplasmacytic infiltration was significantly associated with marked hilar IgG4⁺ staining (P < 0.001). No patient had marked peripheral IgG4⁺ staining, although mild and moderate staining was observed in 24.5% and 3.3% respectively. Marked hilar IgG4⁺ staining was significantly associated with the presence of dominant biliary strictures (P = 0.01) and need for biliary stenting (P = 0.001). There did not, however, exist any significant differences in the age at PSC diagnosis, presence of inflammatory bowel disease or extrahepatic autoimmune disease, frequency of cholangiocarcinoma, interval between diagnosis and transplantation, or post-transplant PSC recurrence or survival. Of 51 control liver sections (PBC = 18; HCV = 19; HBV = 8; AIH = 6), none had marked or moderate hilar IgG4⁺ staining, whereas mild staining was seen in only 10% (P < 0.001). Marked (>50/HPF) hilar IgG4⁺ lymphoplasmacytic infiltration is frequently observed in PSC and associated with the presence of dominant biliary strictures. However, unlike serum IgG4⁺_, this does not seemingly associate with clinical disease course.

Possible involvement of CCL1-CCR8 interaction in lymphocytic recruitment in IgG4-related sclerosing cholangitis

BACKGROUND & AIMS

IgG4-related sclerosing cholangitis and type 1 autoimmune pancreatitis (IgG4-SC/AIP) are characterized by massive lymphoplasmacytic infiltration including Th2 and regulatory T cells (Tregs). This study was conducted to address which chemotactic factors are involved in this condition.

METHODS

Chemokine expression profiles in tissue were examined in IgG4-SC/AIP (n=17), classical primary sclerosing cholangitis (IgG4(low) PSC, n=17), PSC with elevated serum/tissue IgG4 levels (IgG4(high) PSC, n=5), and primary biliary cirrhosis (n=7). We focused on five chemotactic factors/receptors (CCL1-CCR8, CCL17/CCL22-CCR4), given that CCR4 and CCR8 are predominantly expressed in both Th2 and Tregs.

RESULTS

In conjunction with higher expression levels of IL-4 and IL-10, expression values of CCL1 and CCR8 transcripts were significantly higher in IgG4-SC/AIP than in IgG4(low) PSC (p=0.002) and IgG4(high) PSC (p=0.023). CCL1 and CCR8 were also overexpressed in IgG4(high) PSC than in IgG4(low) PSC (p=0.023). No difference was seen for CCL17, CCL22, and CCR4. In situ hybridization revealed CCL1 to be predominantly expressed in the pancreatic duct epithelium, peribiliary glands, and vascular endothelial cells including the ones involved in obliterative phlebitis in IgG4-SC/AIP, in contrast to IgG4(high) PSC where this chemotactic factor was positive in several infiltrating lymphocytes. These CCL1-expressing sites were infiltrated by CCR8(+) lymphocytes. On immunohistochemistry, GATA3(+) Th2 lymphocytes and FOXP3(+) Tregs were significantly larger in number in IgG4-SC/AIP, with the GATA3(+)/T-bet(+) cell ratio to be shifted in favour of Th2 in periductal and perivascular areas.

CONCLUSIONS

CCL1-CCR8 interaction may play a critical role in lymphocytic recruitment in IgG4-SC/AIP, leading to duct-centred inflammation and obliterative phlebitis.

Chronic cholestatic liver diseases: clues from histopathology for pathogenesis

Chronic cholestatic liver diseases include fibrosing cholangiopathies such as primary biliary cirrhosis or primary sclerosing cholangitis. These and related cholangiopathies clearly display pathologies associated with (auto)immunologic processes. As the cholangiocyte's apical membrane is exposed to the toxic actions of the bile fluid, the interaction of bile with cholangiocytes and the biliary tree in general must be considered to completely understand the pathogenesis of cholangiopathies. While the molecular processes involved in the hepatocellular formation of bile are well understood in both normal and pathophysiologic conditions, those in the bile ducts of normal liver and in livers with cholangiopathies lag behind. This survey highlights key mechanisms known to date that are important for the formation of bile by hepatocytes and its modification by the biliary tree. It also delineates the clinical pathophysiologic findings for cholangiopathies and puts them in perspective with current experimental models to reveal the pathogenesis of cholangiopathies and develop novel therapeutic approaches.

A case of Mikulicz's disease complicated by malignant lymphoma: a postmortem histopathological finding

A 66-year-old Japanese man with an 11-year history of Mikulicz's disease (MD) received continuous corticosteroid administration. At age 58, a left renal pelvic mass was identified and diagnosed as an IgG4-related inflammatory pseudotumor. The patient underwent an operation to remove the tumor. Subsequently, he contracted repeated pulmonary infections and eventually died of severe gastrointestinal bleeding. Autopsy revealed systemic lymph node swelling and infiltration in some organs, and diffuse large B-cell lymphoma (DLBCL) was diagnosed. These findings suggest that an IgG4-related disease can be causally related to the development of malignant lymphoma through the occurrence of mucosa-associated lymphoid tissue lymphoma.

Pathogenesis of IgG4-related disease

PURPOSE OF REVIEW

To review studies that have examined underlying genetic and immunological aspects of IgG4-related disease.

RECENT FINDINGS

Genetic studies have suggested that several human leukocyte antigen (HLA) and non-HLA haplotypes/genotypes are associated with susceptibility to IgG4-related disease or to disease relapse after steroid therapy. Among several autoantibodies identified so far, autoantibodies against lactoferrin and carbonic anhydrase II are most frequently detected in serum of IgG4-disease patients. However, it has not been well clarified whether or not those autoantibodies belong to an IgG4 subclass. Studies that have demonstrated molecular mimicry between Helicobacter pylori and constituents of pancreatic epithelial cells suggest that gastric H. pylori infection triggers autoimmune pancreatitis in genetically predisposed individuals through antibody cross-reactivity. Recently, T-helper 2 immune reaction has been suggested to be predominant in IgG4-related disease. Interestingly, regulatory immune reactions are activated in IgG4-related disease, and regulatory cytokines interleukin-10 and transforming growth factor-b have been suggested, respectively, to play important roles in IgG4 class switch and fibroplasia.

SUMMARY

Autoimmunity has been considered the most probable pathogenesis of IgG4-related disease, but has not been completely proved so far. A breakthrough study to detect a specific autoantigen, autoantibody, or pathogen is necessary.

Prevalence of hepatic lesions at post-mortem examination in dogs and association with pancreatitis

OBJECTIVES

To assess the prevalence of canine chronic hepatitis (CH) and other liver diseases in first opinion practice and identify associations with concurrent chronic pancreatitis (CP).

METHODS

One large section of left lateral lobe of liver was taken from 200 unselected canine post-mortem examinations from first opinion practices. Histological changes were categorised based on WSAVA criteria. Prevalence of CH and other liver diseases were calculated. Relative risks (RR) for liver histopathology in association with CP and for CH in different breeds were also calculated.

RESULTS

The prevalence of CH was 12%. Some breeds had an increased RR of CH, although sample sizes were small. Dogs with CP had an increased RR of reactive hepatitis but no significant association with the other liver diseases.

CLINICAL SIGNIFICANCE

CH is common in the first opinion dog population but less common than CP. CP was significantly associated with reactive hepatitis but not CH. Possible breed associations mirrored another recent UK study. Some dogs with CP may be erroneously diagnosed clinically as having CH on the basis of increased serum liver enzymes because of concurrent reactive hepatitis if the diagnosis is not confirmed histologically.

Autoantibodies against the exocrine pancreas in autoimmune pancreatitis: gene and protein expression profiling and immunoassays identify pancreatic enzymes as a major target of the inflammatory process

OBJECTIVES

Autoimmune pancreatitis (AIP) is thought to be an immune-mediated inflammatory process, directed against the epithelial components of the pancreas. The objective was to identify novel markers of disease and to unravel the pathogenesis of AIP.

METHODS

To explore key targets of the inflammatory process, we analyzed the expression of proteins at the RNA and protein level using genomics and proteomics, immunohistochemistry, western blot, and immunoassay. An animal model of AIP with LP-BM5 murine leukemia virus-infected mice was studied in parallel. RNA microarrays of pancreatic tissue from 12 patients with AIP were compared with those of 8 patients with non-AIP chronic pancreatitis.

RESULTS

Expression profiling showed 272 upregulated genes, including those encoding for immunoglobulins, chemokines and their receptors, and 86 downregulated genes, including those for pancreatic proteases such as three trypsinogen isoforms. Protein profiling showed that the expression of trypsinogens and other pancreatic enzymes was greatly reduced. Immunohistochemistry showed a near-loss of trypsin-positive acinar cells, which was also confirmed by western blotting. The serum of AIP patients contained high titers of autoantibodies against the trypsinogens PRSS1 and PRSS2 but not against PRSS3. In addition, there were autoantibodies against the trypsin inhibitor PSTI (the product of the SPINK1 gene). In the pancreas of AIP animals, we found similar protein patterns and a reduction in trypsinogen.

CONCLUSIONS

These data indicate that the immune-mediated process characterizing AIP involves pancreatic acinar cells and their secretory enzymes such as trypsin isoforms. Demonstration of trypsinogen autoantibodies may be helpful for the diagnosis of AIP.

Autoimmune pancreatitis

BACKGROUND

Autoimmune pancreatitis (AIP) is a relatively newly recognized type of pancreatitis that is characterized by diffuse or focal swelling of the pancreas due to lymphoplasmacytic infiltration and fibrosis of the pancreatic parenchyma.

MATERIAL AND METHODS

A PubMed literature search was performed using the keywords "autoimmune pancreatitis". Sometimes, bibliographies were cross-referenced and related article searches were performed once an article of interest was identified.

RESULTS

Pathologically, AIP shows narrowing of the pancreatic ducts and the intrapancreatic portion of the common bile duct. Obstructive jaundice is a common symptom at presentation, and pancreatic cancer represents an important clinical differential diagnosis. In late stages of the disease, the normal pancreatic parenchyma is often replaced by large amounts of fibrosis. Histologically, there seem to be two subtypes of the disease-one showing infiltration with IgG4-positive plasma cells but lacking granulocytic epithelial lesions (GELs), the other showing GELs but lacking strong IgG4 positivity. AIP is in at least some instances the pancreatic manifestation of a clinicopathological entity of IgG4-related systemic sclerosing disease. On the basis of pancreatic imaging, together with serological measurement of IgG4 and evaluation of other organ involvement, many AIP patients can be identified. The remaining patients require further diagnostic work-up. In these patients, pancreatic core needle biopsy and, as AIP responds to steroid treatment, also a trial with steroids, can help to differentiate AIP from pancreatic cancer. OUTLOOK AND DISCUSSION: This review presents the pathological, radiologic and laboratory findings of AIP. Moreover, the treatment and pathogenesis are discussed.

IgG4+ plasma cell infiltrates in liver explants with primary sclerosing cholangitis

Sclerosing cholangitis can be primary (PSC) or secondary. One unusual cause of secondary sclerosing cholangitis is the newly recognized entity of IgG4-associated cholangitis. The prevalence and significance of IgG4 plasma cells in patients, who are clinically and radiologically classified as PSC, however, are unknown. Clinical information and histology of liver explants of 98 consecutive liver transplants performed for PSC were reviewed. IgG4 immunohistochemical stain was performed on sections from hilar areas that contained large bile ducts and corresponding cholecystectomy specimens (available in 74 cases). Serum IgG4 levels were measured in stored serum from 81 cases. Tissue IgG4 positivity (>or=10 IgG4+ plasma cells/high power field) was correlated with clinical features (age, sex, presence of inflammatory bowel disease and cholangiocarcinoma, pancreatogram, PSC duration, PSC recurrence after transplant, and number of acute rejection episodes) and histologic findings (periductal lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis) in the liver explants. Twenty-three (23%) liver explants showed periductal infiltration with IgG4+ plasma cells. Eighteen cases (22%) had elevated serum IgG4 levels, including 8 without tissue IgG4 positivity. All cases showed dense periductal fibrosis; none had storiform fibrosis or obliterative phlebitis. IgG4 positivity in the liver strongly correlated with moderate-to-marked periductal lymphoplasmacytic inflammation (P=0.002). Clinically, IgG4 positivity in tissue, but not in serum, was correlated with shorter PSC duration before transplant and higher risk of recurrence after transplant. Nearly one quarter of explanted livers that carry a clinical diagnosis of PSC contain increased IgG4+ periductal plasma cell infiltrates and positive serum IgG4 levels. However, none of the explants show histologic features diagnostic of IgG4-associated cholangitis. PSC with tissue IgG4 positivity has a more aggressive clinical course manifested by shorter time to transplant and a higher likelihood of recurrence than IgG4 negative PSC.

Incidence, clinical presentation and pathological features of benign sclerosing cholangitis of unknown origin masquerading as biliary carcinoma

BACKGROUND

Benign obstructions of the liver hilum are occasionally encountered in surgically resected cases. Some of these cases are pathologically classified as benign sclerosing cholangitis and are not clearly categorized. This study aims to elucidate the clinicopathological features of benign sclerosing cholangitis of unknown origin.

METHODS

Patients who had undergone surgery of the proximal bile duct from 1993 to 2008 on suspicion of proximal bile carcinoma were evaluated, then their clinical presentation, histopathological and immunohistochemical findings were retrospectively analyzed.

RESULTS

One hundred seventy-six patients underwent surgery during this period. Of these, five patients were diagnosed with benign sclerosing cholangitis of unknown origin. All five patients were middle-aged with no history of autoimmune disease. One patient died of recurrent cholangitis after surgery. Histopathologically, lymphoplasmacytic infiltrations were observed in all five cases. Among them, the clinicopathological findings of one patient were compatible with IgG4-related sclerosing cholangitis, and the other two patients had unusual histopathological findings with prominent lymph follicular formation.

CONCLUSIONS

Although patients with benign sclerosing cholangitis of unknown origin comprise a heterogeneous population, they can be further classified into subgroups. The response to immunosuppressive therapy, long-term prognosis and histological morphology of the disease should be considered in order to classify these cases of sclerosing cholangitis.