Paraduodenal pancreatitis: a clinico-pathologically distinct entity unifying "cystic dystrophy of heterotopic pancreas", "para-duodenal wall cyst", and "groove pancreatitis"

Pancreatic Cystic Lesions of Nonmucinous Type

Cystic lesions of nonmucinous type can arise within the pancreas or can develop from adjacent structures and appear to involve the pancreas. In addition, some typically solid masses can become cystic or can present as cystic lesions. Nonmucinous cysts can be neoplastic, inflammatory, reactive, or congenital. The vast majority of neoplastic nonmucinous cysts are benign. Because of the difficulty in determining the neoplastic potential of a pancreatic cyst preoperatively, many non-neoplastic cysts are resected. This article reviews the surgical pathology of nonmucinous cysts.

Pancreatitis, Other Inflammatory Lesions, and Pancreatic Pseudotumors

The pancreas is versatile in the diversity of disorders that it can exhibit. In this article, characteristics of disorders such as chronic, autoimmune, eosinophilic, hereditary, and infectious pancreatitis are described. With regard to autoimmune pancreatitis, the role of clinical evaluation, histologic examination, and IgG4 immunohistochemistry is discussed. The role of pancreatitis in the pathogenesis of diabetes is also mentioned. Some implications of pancreatitis are highlighted, including the neoplastic predisposition caused by inflammatory lesions of the pancreas. The goal of this article is to convey an appreciation of these disorders because their recognition can benefit patients tremendously, as inflammatory lesions of the pancreas can be mass-forming, giving rise to pseudotumors, and leading to surgical resection that may otherwise be unnecessary.

Ductal Adenocarcinoma of the Pancreas

Pancreatic ductal adenocarcinoma (PDAC) and its variants comprise between 80% and 90% of all tumors of the exocrine pancreas. Because of its silent course, late clinical manifestation, and rapid growth, it is considered a silent killer. Only 10% to 15% of cases are resectable and the 5-year survival rate remains lower than 5%. The differential diagnosis between PDAC and chronic pancreatitis is a challenge for pathologists. This article provides a guide for pathologic evaluation of PDAC specimens with the macroscopic and microscopic features of common PDAC and its variants and discusses the differential diagnosis and morphologic and immunophenotypical prognostic parameters.

Characteristic clinical and pathologic features for preoperative diagnosed groove pancreatitis

Purpose

Groove pancreatitis is a rare specific form of chronic pancreatitis that extends into the anatomical area between the pancreatic head, the duodenum, and the common bile duct, which are referred to as the groove areas. We present the diagnostic modalities, pathological features and clinical outcomes of a series of symptomatic patients with groove pancreatitis who underwent pancreaticoduodenectomy.

Methods

Six patients undergoing pancreaticoduodenectomy between May 2006 and May 2009 due to a clinical diagnosis of symptomatic groove pancreatitis were retrospectively included in the study.

Results

Five cases were male and one case was female, with a median age at diagnosis of 50 years. Their chief complaints were abdominal pain and vomiting. Abdominal computed tomography, endoscopic ultrasound and endoscopic retrograde cholangiopancreatography were performed. Preoperative diagnosis of all patients was groove pancreatitis. Histological finding was compatible with clinically diagnosed groove pancreatitis in five patients and the pathologic diagnosis of the remaining patient was adenocarcinoma of distal common bile duct. Following pancreaticoduodenectomy, four living patients experienced significant pain alleviation.

Conclusion

The diagnostic imaging modalities of choice for groove pancreatitis are computed tomography and endoscopic ultrasonography. If symptomatic groove pancreatitis is suspected, careful follow-up of patients is necessary and pancreaticoduodenectomy seems to be a reasonable treatment option.

Complications of congenital and developmental abnormalities of the gastrointestinal tract in adolescents and adults: evaluation with multimodality imaging

There is a wide variety of congenital anomalies that may affect the gastrointestinal tract. Most symptomatic congenital anomalies are found in newborns and infants. Such anomalies are relatively rare in adolescents and adults, and they may be difficult to identify because clinical symptoms often are nonspecific and insidious, causing them to be mistaken for other common abdominal conditions. Multimodality imaging is useful in evaluating congenital anomalies of the gastrointestinal tract in adults. The imaging features at radiography, fluoroscopy, ultrasonography, computed tomography, and magnetic resonance imaging may help identify congenital gastrointestinal anomalies such as congenital esophageal stenosis, gastric volvulus, duodenal web, annular pancreas, heterotopic pancreas, cecal volvulus, anomalies of the omphalomesenteric duct, Hirschsprung disease, and gastrointestinal duplication cyst. Familiarity with the imaging features of the various congenital anomalies of the gastrointestinal tract and their complications is important to establish the correct diagnosis and determine appropriate treatment, which is critical to avoid life-threatening complications.

Gastrointestinal Hemorrhage Secondary to Duodenal Cystic Dystrophy in Heterotopic Pancreas

Cystic dystrophy of the duodenal wall (CDDW) is a complication of heterotopic pancreatic tissue located in the wall of the gastrointestinal tract, characterized by the presence of multiple small cysts, usually found in the wall of the second part of the duodenum. Gastrointestinal hemorrhage due to CDDW is a rare complication. We report the case of a 50-year-old man who was admitted to our hospital for persistent vomiting. The imaging tests confirmed the diagnosis of CDDW. During his stay in hospital, the patient had a gastrointestinal hemorrhage secondary to this disorder, which made it necessary to perform a Roux-en-Y gastrojejunostomy (Billroth III).

Sonographic findings in groove pancreatitis

Groove pancreatitis is a rare form of chronic pancreatitis involving the anatomic plane between the pancreatic head and duodenum. The radiographic diagnosis remains challenging, and most patients undergo exploratory laparotomy on suspicion of a periampullary malignancy. The appearance of groove pancreatitis on transabdominal and intraoperative sonography has rarely been reported in the literature. The sonographic findings in our 2 patients included a hypoechoic thin area between the pancreatic head and duodenum, a hyperechoic and thickened wall of the adjacent duodenum, and a heterogeneous or hyperechoic dorsocranial part of the pancreatic head.

Pancreatitis of the gastroduodenal groove: a case report

Groove pancreatitis, a form of chronic pancreatitis affecting the head of the pancreas, is localized within the groove between the pancreas head, duodenum, and common bile duct. We report a case of a male patient with groove pancreatitis who initially underwent a duodenal preserving gastrenteranastomosis. Unfortunately, the patient's symptoms were only partially controlled, necessitating a pancreaticoduodenectomy in due course as the definite surgical restoration procedure. The surgical approach selected proved inadequate since the patient's symptoms did not resolve over time. This reflects that by-pass operations like these are not indicated for the management of patients with groove pancreatitis.

"Paraduodenal" pancreatitis: results of surgery on 58 consecutives patients from a single institution

BACKGROUND

Cystic dystrophy of heterotopic pancreas, groove pancreatitis, pancreatic hamartoma of the duodenum, paraduodenal wall cyst, and myoadenomatosis are all terms grouped together, from a pathological viewpoint, as definitions of paraduodenal pancreatitis (PP). The objective of the present study was to investigate the clinical characteristics, therapeutic strategies, and results in 58 patients undergoing pancreatic resection for PP.

METHODS

From January 1990 to December 2006 data were prospectively collected on 58 patients who were diagnosed with PP who then underwent pancreaticoduodenectomy.

RESULTS

In this patient cohort the median age was 44.7 years; only 4 patients were women, and only 3 had non-drinker and/or non smoker habits. The overall morbidity was 18.9%, and the median hospitalization was 11 days. There were no postoperative deaths. In a median follow-up of 96.3 months, all patients noted a decrease in the pain associated with PP; 35 patients (76%) had complete disappearance of pain, whereas occasional relapsing pain occurred in the remaining 11 (24%).

CONCLUSIONS

Patients with PP have clinical characteristics similar to those of chronic pancreatitis. The diagnostic imaging modalities of choice are ultrasonographic endoscopy and magnetic resonance cholangiopancreaticography. Based on our surgical experience, pancreaticoduodenectomy seems to be a reasonable choice of treatment in patients with PP.

Nonalcoholic, nonbiliary pancreatitis: cross-sectional imaging spectrum

OBJECTIVE

The purpose of this review is to describe the epidemiologic, etiopathogenetic, clinical, and imaging characteristics of various nonalcoholic, nonbiliary pancreatitis syndromes.

CONCLUSION

The spectrum of nonalcoholic, nonbiliary pancreatitis includes autoimmune pancreatitis, groove pancreatitis, hereditary pancreatitis, tropical pancreatitis, tuberculous pancreatitis, and metabolic pancreatitis. Advances in genetics and molecular pathology have shed new light on the etiopathogenesis and course of these syndromes. Accurate diagnosis aided by imaging findings allows optimal management.

A clinical and radiologic review of uncommon types and causes of pancreatitis

Acute pancreatitis is one of the most common conditions for which emergent imaging is indicated. Alcohol consumption and cholelithiasis are the most common causes of acute pancreatitis in adults, whereas the majority of cases in children are idiopathic or secondary to trauma. A wide variety of structural and biochemical abnormalities may also cause pancreatitis. Although in some cases it is difficult to identify the specific cause of the disease radiologically, certain uncommon types of acute or chronic pancreatitis may have unique imaging features that can help the radiologist make an accurate diagnosis. These unusual types include autoimmune pancreatitis, groove pancreatitis, tropical pancreatitis, hereditary pancreatitis, and pancreatitis in ectopic or heterotopic pancreatic tissue. Pancreatitis may occasionally be seen in association with cystic fibrosis or pancreas divisum, or secondary to worm infestation of the pancreaticobiliary tree (eg, by Ascaris lumbricoides). In addition, primary pancreatic and duodenal masses may occasionally manifest as acute or recurrent acute pancreatitis. Knowledge of the classic imaging findings of these entities allows prompt recognition of the relevant pathologic condition, thereby preventing misdiagnosis and subsequent inappropriate or delayed management.

A comprehensive, case-based review of groove pancreatitis

Groove pancreatitis is an uncommon form of focal chronic pancreatitis that involves the duodenal wall or "groove" area (between the pancreas, common bile duct, and duodenum). It remains largely an unfamiliar entity to most physicians and is often misdiagnosed as pancreatic malignancy or autoimmune pancreatitis because of its "pseudotumor" formation. In this case series, we present 4 cases of groove pancreatitis which highlight important clinical aspects of this disease entity. We then provide a review of the pathophysiology, diagnosis, and treatment of this condition. We hope to clarify the salient aspects of this disease process and make groove pancreatitis a more recognized entity to the clinician.

Pancreatic cysts: pathologic classification, differential diagnosis, and clinical implications

CONTEXT

Cystic lesions of the pancreas are being recognized with increasing frequency and have become a more common finding in clinical practice because of the widespread use of advanced imaging modalities and the sharp drop in the mortality rate of pancreatic surgery. Consequently, in the past 2 decades, the nature of many cystic tumors in this organ has been better characterized, and significant developments have taken place in the classification and in our understanding of pancreatic cystic lesions.

OBJECTIVE

To provide an overview of the current concepts in classification, differential diagnosis, and clinical/biologic behavior of pancreatic cystic tumors.

DATA SOURCES

The authors' personal experience, based on institutional and consultation materials, combined with an analysis of the literature.

CONCLUSIONS

In contrast to solid tumors, most of which are invasive ductal adenocarcinomas with dismal prognosis, cystic lesions of the pancreas are often either benign or low-grade indolent neoplasia. However, those that are mucinous, namely, intraductal papillary mucinous neoplasms and mucinous cystic neoplasms, constitute an important category because they have well-established malignant potential, representing an adenoma-carcinoma sequence. Those that are nonmucinous such as serous tumors, congenital cysts, lymphoepithelial cysts, and squamoid cyst of pancreatic ducts have no malignant potential. Only rare nonmucinous cystic tumors that occur as a result of degenerative/necrotic changes in otherwise solid neoplasia, such as cystic ductal adenocarcinomas, cystic pancreatic endocrine neoplasia, and solid-pseudopapillary neoplasm, are also malignant and have variable degrees of aggressiveness.

Nonneoplastic mimickers of pancreatic neoplasms

CONTEXT

A variety of nonneoplastic conditions may form pancreatic masses that mimic carcinoma. Approximately 5% to 10% of pancreatectomies performed with the clinical diagnosis of pancreatic cancer prove on microscopic evaluation to be pseudotumors.

OBJECTIVES

To illustrate the clinical and pathologic characteristics of the 2 most frequent pseudotumoral inflammatory conditions, autoimmune pancreatitis and paraduodenal pancreatitis, and describe the criteria that may be useful in the differential diagnosis versus pancreatic carcinoma.

DATA SOURCES

Recent literature and the authors' experience with the clinical and pathologic characteristics of autoimmune pancreatitis and paraduodenal pancreatitis.

CONCLUSIONS

The knowledge of the clinical, radiologic, and pathologic findings in both autoimmune pancreatitis and paraduodenal pancreatitis is crucial in making the correct preoperative diagnosis. Autoimmune pancreatitis, which occurs in isolated or syndromic forms, is characterized by a distinctive fibroinflammatory process that can either be limited to the pancreas or extend to the biliary tree. Its correct preoperative identification on biopsy material with ancillary immunohistochemical detection of dense immunoglobulin G4-positive plasma cell infiltration is possible and crucial to prevent major surgery and to treat these patients with steroid therapy. Paraduodenal pancreatitis is a special form of chronic pancreatitis that affects young males with a history of alcohol abuse and predominantly involves the duodenal wall in the region of the minor papilla. Pathogenetically, the anatomical and/or functional obstruction of the papilla minor, resulting from an incomplete involution of the intraduodenal dorsal pancreas, associated with alcohol abuse represents the key factor. Endoscopic drainage of the papilla minor, with decompression of the intraduodenal and dorsal pancreas, might be considered in these patients.

Groove pancreatitis: a diagnostic challenge

Groove pancreatitis is a distinct form of chronic pancreatitis characterized by inflammation and fibrous tissue formation, affecting the groove area between the head of the pancreas, the duodenum and the common bile duct. It is manifested on imaging by a sheet-like mass in the groove area near the minor papilla. Thickening of the duodenal wall and cystic transformation in the duodenal wall also represent common imaging features. Pathogenesis is still unclear, and clinical presentation is not specific. Endoscopic ultrasonography (EUS), computed tomography (CT) and magnetic resonance imaging (MRI) demonstrate imaging findings consistent with the disease in typical cases, but specific diagnosis is challenging in a number of patients where biopsy is required. The disease may mimic pancreatic, common bile duct or duodenal wall cancer that requires prompt and excessive surgical intervention, as opposed to groove pancreatitis where initial conservative treatment is suggested. The clinical, histopathological and radiological features on cross-sectional imaging of this entity are discussed in this review, and differential diagnostic clues are given.

Clinical and radiological outcome of patients suffering from chronic pancreatitis associated with gene mutations

OBJECTIVES

Cystic fibrosis transmembrane conductance regulator (CFTR), cationic trypsinogen gene (PRSS1), and serine protease inhibitor kazal type 1 (SPINK1) gene mutations have been associated with chronic pancreatitis (CP). The aim of this study was to compare clinical and radiological findings in sporadic CP with (CPgm) and without (CPwt) gene mutations.

METHODS

Data from patients observed between 2001 and 2006 were collected. All patients were tested for 25 CFTR gene mutations, for R122H and N29I on the PRSS1 gene, and for N34S mutation on the SPINK1 gene.

RESULTS

We found 34 (17.2%) of 198 patients with CPgm, 23 (11.6%) of them on the CFTR gene, 11 (5.6%) on the SPINK1, and none on the PRSS1 gene. The age at clinical onset was younger in CPgm (36.2 +/- 17.2 years) than in CPwt (44 +/- 12.6 years; P = 0.005). There were more heavy drinkers among CPwt (33%) than among CPgm (9%; P = 0.003), and the same applied to smokers (69% vs 33%, respectively; P < 0.0001). In CPgm group, the onset of pancreatic calcifications was observed more frequently in drinkers and/or smokers. Exocrine and endocrine insufficiency occurred less frequently and later in CPgm than in CPwt patients.

CONCLUSIONS

Clinical and radiological outcome differ in CPgm compared with CPwt. Alcohol, even in small quantities, and cigarette smoking influence the onset of pancreatic calcifications.

Multicystic adenomatoid hamartoma of the pancreas: a hitherto undescribed pancreatic tumor occurring in a 3-year-old boy

This report describes an unusual pancreatic tumor in a 3-year-old boy. He presented with abdominal pain secondary to pancreatitis and was found to have a complex, multicystic lesion within the head of the pancreas. He subsequently underwent a pancreatoduodenectomy. Grossly, the mass was 3 cm, multicystic, and well demarcated. Histologically, there were numerous variably sized, dilated ducts lined by tall columnar mucinous cells surrounded by a stroma that exhibited foci of cellular condensations resembling primitive pancreatic mesenchyme. Acinar and endocrine cells were often seen budding into the ducts forming "ductulo-insular bodies." As a result of its superficial resemblance to Stocker type 2 cystic adenomatoid malformation of the lung, we are proposing the name "multicystic adenomatoid hamartoma" for this lesion.

Groove pancreatitis: MRI and pathologic findings

OBJECTIVE

Our purpose is to describe the MRI findings with pathologic correlation, in five patients with groove pancreatitis, a specific form of chronic pancreatitis affecting the groove between the pancreatic head, the common bile duct and duodenum.

MATERIALS AND METHODS

Five patients with pathologically proven (four cases) and clinical and MRI findings (follow-up) consistent with the diagnosis of groove pancreatitis (one case) were reviewed. Three patients underwent cephalic pancreatoduodenectomy (Whipple procedure) due to severe duodenal stenosis; MRI findings were correlated with the histological findings.

RESULTS

In all patients a mass was seen affecting the groove between the pancreatic head and the duodenum. Precontrast images demonstrated hypointense tissue relative to pancreatic parenchyma on T1-weighted images and iso to slightly hyperintense tissue on STIR and T2-weighted images. Postcontrast dynamic Gd-DTPA images, showed peripheral mass enhancement on immediate postgadolinium images and progressive and centripetal mass enhancement on delayed images with good delineation of multiple cysts. Histologically, fibro-inflammatory tissue was demonstrated in the groove and the duodenal wall with obliterative concentric scarring of the distal common bile duct.

CONCLUSIONS

MRI findings are demonstrative of the pathologic features characteristic of this entity: the fibrous tissue in the pancreaticoduodenal groove, the duodenal wall inflammation and the groove and/or duodenal wall cyst formation.

MRI features of groove pancreatitis

OBJECTIVE

The purpose of this article is to discuss and illustrate the most relevant and unique MRI features of groove pancreatitis.

CONCLUSION

Groove pancreatitis in an uncommon type of focal chronic pancreatitis. Its appearance may resemble pancreatic adenocarcinoma. Although distinction between these two entities remains challenging, knowledge of MRI findings is important in suggesting the correct diagnosis and programming therapeutic decisions.

Clinical and morphological features of duodenal cystic dystrophy in heterotopic pancreas

BACKGROUND AND AIMS

Cystic dystrophy in heterotopic pancreas (CDHP) is an uncommon complication of pancreatic heterotopia, only described in surgical series, whose natural history is not known. The aim of this study was to determine clinical and morphological features of CDHP in a medical-surgical series of patients and to ascertain the relationship of CDHP with chronic pancreatitis (CP) in the pancreas proper.

METHODS

All patients who had duodenal CDHP diagnosed radiologically both with CT scan and endoscopic ultrasonography between 1995 and 2004 were included. The diagnosis was confirmed by surgical specimens when available.

RESULTS

One hundred five patients were included (91% men, 86% chronic alcoholic) with a median follow-up of 15 months. The median age at first symptoms was 46 yr. CDHP was associated with CP in the pancreas proper in 71% of patients. Presenting symptoms were pancreatic pain (91%), severe weight loss (73%), acute pancreatitis (45%), vomiting (30%), steatorrhea (23%), diabetes mellitus (20%), jaundice (13%), and upper gastrointestinal hemorrhage (5%). Cysts were multiple in 75% (median 3). The median diameter of the largest cyst was 10 mm. Endoscopy was normal in 36% of patients and showed duodenal stenosis in 52% (complete 6%, incomplete 46%). Surgical treatment was necessary in only 27% of patients (Whipple procedure 16%).

CONCLUSIONS

CDHP may arise in patients with or without CP and with or without chronic alcoholism. Symptoms may be severe but warrant surgery in less than one-third of patients.

Chronic pancreatitis, pseudotumors and other tumor-like lesions

Chronic pancreatitis is a fibroinflammatory disease of the pancreas. Etiologically, most cases are related to alcohol abuse and smoking. Recently, gene mutations have been identified as the cause of hereditary pancreatitis. Other chronic pancreatitis types that were defined in recent years are autoimmune pancreatitis (lymphoplasmacytic sclerosing pancreatitis) and paraduodenal pancreatitis ('groove pancreatitis', 'cystic dystrophy of heterotopic pancreas'). This review describes and discusses the main histological findings, the pathogenesis and the clinical features of the various types of chronic pancreatitis. In addition, pseudotumors and other tumor-like lesions are briefly mentioned.

Cystic lesions of the pancreas

Although cystic tumors of the pancreas are relatively rare, they constitute an increasingly important category. Advances in imaging and interventional techniques and the sharp drop in the mortality rate of pancreatic surgery have rendered pancreatic biopsies and resections commonplace specimens. Consequently, in the past two decades, the nature of many cystic tumors in this organ has been better characterized. The names of some existing entities were revised; for example, what was known as papillary-cystic tumor is now regarded as solid-pseudopapillary tumor. New entities, in particular, intraductal papillary mucinous neoplasm and its variants, such as oncocytic and intestinal subtypes were recognized. The importance of clinical and pathologic correlation in the evaluation of these lesions was appreciated, in particular, with regards to the multifocality of these lesions, their association with invasive carcinomas, and thus their 'preinvasive' nature. Consensus criteria for the distinction of these from the ordinary precursors of adenocarcinoma, the pancreatic intraepithelial neoplasia, were established. The definition of mucinous cystic neoplasms was refined; ovarian-like stroma has now become almost a requirement for the diagnosis of mucinous cystic neoplasia, and defined as such, the propensity of these tumors to occur in perimenopausal women became even more striking. The validity and clinical value of classifying the pancreatic cysts of mucinous type as adenoma, borderline, CIS and invasive have been established. Related to this, the importance of thorough sampling in accurate classification of these mucinous lesions was recognized. Greater accessibility of the pancreas afforded by improved invasive as well as noninvasive modalities has also increased the detection of otherwise clinically silent cystic tumors, which has led to the recognition of more innocuous entities such as acinar cell cystadenoma and squamoid cyst of pancreatic ducts. As the significance of the cystic lesions emerged, cystic forms of otherwise typically solid tumors were also better characterized. Thus, significant developments have taken place in the classification and our understanding of pancreatic cystic tumors in the past few years, and experience with these lesions is likely to grow exponentially in the coming years.

Toward a new classification of chronic pancreatitis

Pancreatitis is divided into acute and chronic types. In recent years several classification schemes have been proposed which focus on the clinical, imaging, or morphological features of the disease. Because etiology has also become an important criterion for the characterization of pancreatitis, a classification proposal is presented that attempts to include all relevant features of the disease: clinical presentation, outcome, pathology, and etiology.

Pancreatic pseudotumors: non-neoplastic solid lesions of the pancreas that clinically mimic pancreas cancer

In the pancreas, a variety of non-neoplastic conditions may form solid masses that may mimic cancer. Up to 5% of pancreatectomies performed with the preoperative clinical diagnosis of carcinoma will prove to be non-neoplastic by pathologic examination, although this figure is decreasing with improved diagnostic modalities. Chronic inflammatory lesions are the leading cause of this phenomenon ("pseudotumoral pancreatitis"), and among these, autoimmune and paraduodenal pancreatitides (discussed separately in this issue) are most important. In this article, we will focus on the noninflammatory lesions that may form tumor-like lesions of the pancreas. Adenomyomatous hyperplasia of ampulla of Vater is a subtle lesion that is difficult to define; larger examples (>5 mm) have been found to be the cause of obstructive jaundice. Accessory (heterotopic) spleen may form a well-defined nodule within the tail of the pancreas and is typically mistaken for endocrine neoplasm. Lipomatous hypertrophy is the replacement of pancreatic tissue with mature adipose tissue that occasionally leads to moderate to marked enlargement of the pancreas. Hamartomas are very rare if the entity is defined strictly. They are characterized by irregularly arranged mature pancreatic elements admixed with stromal tissue. A cellular, spindle-cell variant with c-kit (CD117) expression is recognized. Pseudolymphoma forms well-defined nodules composed of hyperplastic lymphoid tissue. Rarely, foreign-body deposits, granulomatous inflammations (such as sarcoidosis or tuberculosis), and congenital lesions may form tumoral lesions. In conclusion, it is important to recognize the types of conditions that form pseudotumors in the pancreas so that they can be distinguished from ductal adenocarcinomas, especially clinically, but also pathologically. Nonspecific terms such as "inflammatory pseudotumor" ought to be avoided, and every attempt should be made to classify a "pseudotumor" into a more specific diagnostic category discussed above.

Diagnostic features and differential diagnosis of autoimmune pancreatitis

A clinically and pathologically distinct form of chronic pancreatitis is now widely recognized and has been designated variably as lymphoplasmacytic sclerosing pancreatitis, duct-destructive (duct-centric) pancreatitis or autoimmune pancreatitis. This entity is currently defined by a constellation of clinical and pathologic findings, including the lack of both conventional risk factors for pancreatitis, such as alcohol use and gallstones, and their hallmark pattern of injury, including calcifications and pseudocysts. 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). 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. This type of pancreatitis is considered an autoimmune process. In about 15% to 20% of patients, the clinical stigmata of 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." In fact, this entity accounts for more than a third of the cases of pseudotumoral pancreatitis (mass-forming inflammatory lesions that resemble carcinoma). Elevated serum IgG4 levels are characteristic and may be very helpful in the differential diagnosis from tumors and tumor-like lesions of the pancreas which seldom result in levels above 135 mg/dL. 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 afflicted as commonly as (if not more than) females. Following resection, emergence of new fibro-inflammatory lesions in the remaining pancreaticobiliary tree has been noted in some cases; however, the process typically responds to steroids. It is important to recognize the distinctive clinicopathologic features of this entity, so that it can be diagnosed accurately and managed appropriately.