Histopathological study on mechanism and background of tumor-forming pancreatitis

Limited efficacy of (18)F-FDG PET/CT for differentiation between metastasis-free pancreatic cancer and mass-forming pancreatitis

OBJECTIVE

Differentiation between metastasis-free pancreatic cancer and mass-forming pancreatitis is important to avoid unnecessary operative procedures. This study was aimed at evaluating the efficacy of PET/CT with F-FDG (FDG PET/CT) for the differential diagnosis between them.

PATIENTS AND METHODS

FDG-PET/CT was performed in 47 study patients with pancreatic masses and without any detectable metastases, 33 of which cases were finally diagnosed as pancreatic cancer and the other 14 as pancreatitis, and the corresponding imaging data were evaluated retrospectively. The maximal SUV (SUVmax) within the masses were determined at 1 hour and mostly at 2 hours after intravenous injection of FDG.

RESULTS

SUVmax at 1 hour in pancreatic cancer was significantly higher than that in mass-forming pancreatitis, and the change in SUVmax from 1- to 2-hour time points was more consistent with pancreatic cancer than with mass-forming pancreatitis. However, there remained considerable overlapping between the SUVmax values of both diseases except either at the higher range for pancreatic cancer (> 7.7 at 1 hour or > 9.98 at 2 hours) or at the lower range for mass-forming pancreatitis (<3.37 at 1 hour or <3.53 at 2 hours). No obvious difference was found in the FDG uptake patterns of the mass areas between both diseases.

CONCLUSIONS

Differentiation between metastasis-free pancreatic cancer and mass-forming pancreatitis is difficult by FDG-PET/CT due to considerable overlapping between the SUVmax values of the two diseases, although the differential diagnosis may be possible either at the higher range of SUVmax (> 7.7 at 1 hour or > 9.98 at 2 hours) for pancreatic cancer or at the lower range of SUVmax (<3.37 at 1 hour or <3.53 at 2 hours) for mass-forming pancreatitis.

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.

Quantitative analysis of diffusion-weighted magnetic resonance imaging of the pancreas: usefulness in characterizing solid pancreatic masses

PURPOSE

To evaluate whether measurement of apparent diffusion coefficient (ADC) and pure diffusion coefficient (D) can help to characterize solid pancreatic masses.

MATERIALS AND METHODS

Diffusion-weighted MR imaging was performed in both a patient group (n = 71; pancreatic cancer [n = 47], mass-forming pancreatitis [n = 13], solid pseudopapillary neoplasm [n = 6], and neuroendocrine tumor [n = 5]) and a normal control group (n = 11) by applying three b-factors of 0, 500, and 1000 sec/mm(2). ADC(500), ADC(1000), D (ADC using b = 500 and 1000 sec/mm(2)), and perfusion fraction (f, 1- exp [-500 sec/mm(2) x (ADC(500) - D)]) of normal pancreas, pancreatic cancer, and mass-forming pancreatitis were compared using the Kruskal-Wallis test. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance and optimal cutoff value of these parameters in differentiating pancreatic cancer from mass-forming pancreatitis.

RESULTS

Normal pancreas had significantly higher mean ADC(500), ADC(1000), and f than either pancreatic cancer (P < 0.001, < 0.001, and 0.004, respectively) or mass-forming pancreatitis (P < 0.001, < 0.001, and 0.002, respectively). ADC(500), ADC(1000), and D of mass-forming pancreatitis were significantly lower than those of pancreatic cancer (P = 0.002, 0.004, and 0.014, respectively). Sensitivities and specificities in the diagnosis of pancreatic cancer were 72.3% and 76.9% for ADC(500), 87.2% and 69.2% for ADC(1000), 87.2% and 61.5% for D, and 42.6% and 92.3% for f, respectively.

CONCLUSION

Measurement of ADC and D may be helpful in differentiating pancreatic cancers from mass-forming pancreatitis.

Strategy for differentiating autoimmune pancreatitis from pancreatic cancer

OBJECTIVES

It is of utmost importance that autoimmune pancreatitis (AIP) be differentiated from pancreatic cancer (PC) because some AIP cases undergo unnecessary laparotomy or pancreatic resection on suspicion of PC. This study aimed to develop an appropriate strategy for differentiating between AIP and PC.

METHODS

Clinical, serological, and radiological features of 17 AIP patients forming a masslike lesion on pancreas head and 70 patients with pancreatic head cancer were compared.

RESULTS

Numerous findings can be used to distinguish between AIP and PC, and the following are more likely in AIP: fluctuating jaundice; elevated serum IgG4 levels; delayed enhancement of the enlarged pancreas and a capsule-like low-density rim on computed tomography; long or skipped narrowed portion with side branches of the main pancreatic duct without upstream dilatation on endoscopic retrograde pancreatography, extrapancreatic lesions, such as stenosis of the intrahepatic bile duct, salivary gland swelling, and retroperitoneal mass; and responsiveness to steroid therapy.

CONCLUSIONS

In elderly male patients presenting with obstructive jaundice and a pancreatic mass, AIP should be considered in the differential diagnosis. Based on a combination of clinical, serological, and radiological findings, AIP can be differentiated from PC. An algorithm for management of patients with a masslike lesion on pancreas head is presented.

Autoimmune pancreatitis: with special reference to a localized variant

In 2006, the Japan Pancreas Society revised the diagnostic criteria for autoimmune pancreatitis (AIP) so as to more clearly define its morphological, pathological, and immunological features, as follows: (1) diffuse or segmental narrowing of the main pancreatic duct with an irregular wall and diffuse or localized enlargement of the pancreas recognized by imaging studies; (2) high serum gamma globulin, IgG, or IgG4 levels, or the presence of autoantibodies; and (3) marked interlobular fibrosis and prominent infiltration of lymphocytes and plasma cells in the periductal area, occasionally with lymphoid follicles in the pancreas. Establishing a diagnosis of AIP has become easier with knowledge of its immunological abnormalities, including serum IgG4 levels. However, the localized form of AIP sometimes mimics pancreatic cancer. The rate of focal mass formation in patients with AIP is reportedly 24%-43%; however, there have been few reports on the histological findings of localized AIP, in contrast to mass-forming pancreatitis (MFP). Our review of patients who had undergone resection due to a preoperative diagnosis of MFP with possible cancer revealed 72% to be patients with localized AIP. For the discrimination of these conditions, it is important to recognize the characteristic ultrasonographic findings of AIP, i.e., (1) diffuse or localized enlargement and hypoechogenicity of the pancreas; (2) rarity of calcification, cystic lesions, and peripancreatic fluid collection; (3) thickened layer structure of the bile duct wall; (4) iso/hypervascularity in the swollen portion of the pancreas; (5) attenuation of pancreatic swelling and bile duct wall thickening after steroid therapy; and (6) multiple hypoechoic masses in various organs, including the pancreas. Contrast-enhanced endoscopic ultrasonography is potentially a useful tool in the differential diagnosis and for assessment of the efficacy of steroid therapy by enabling evaluation of the vascularity of the lesions. Along with the presence of IgG4-positive plasma cells, verification of obliterative phlebitis is highly specific for the histological diagnosis of AIP.

Acute recurrent pancreatitis: An autoimmune disease?

In this review article, we will briefly describe the main characteristics of autoimmune pancreatitis and then we will concentrate on our aim, namely, evaluating the clinical characteristics of patients having recurrence of pain from the disease. In fact, the open question is to evaluate the possible presence of autoimmune pancreatitis in patients with an undefined etiology of acute pancreatitis and for this reason we carried out a search in the literature in order to explore this issue. In cases of recurrent attacks of pain in patients with “diopathic”pancreatitis, we need to keep in mind the possibility that our patients may have autoimmune pancreatitis. Even though the frequency of this disease seems to be quite low, we believe that in the future, by increasing our knowledge on the subject, we will be able to diagnose an ever-increasing number of patients having acute recurrence of pain from autoimmune pancreatitis.

Lymphoplasmacytic sclerosing pancreatitis forming a localized mass: a variant form of autoimmune pancreatitis

BACKGROUND

To elucidate the correlation of autoimmune pancreatitis (AIP) and mass-forming pancreatitis, in which a localized mass is formed in the pancreas.

METHODS

Nine cases of mass-forming pancreatitis were divided into two groups, one consisting of cases that met the histological diagnostic criteria for AIP by the Japan Pancreas Society (JPS) and the other consisting of cases which did not. Histological findings, immunohistological findings, and pancreatograms were compared between these groups.

RESULTS

Six cases met the histological criteria of JPS (group A) and the other three did not (group B). In the mass-forming portion in group A, the wall of the pancreatic duct showed marked thickening. However, the epithelium was well preserved, and dilatation of the branch ducts or protein plugs were rarely observed. All cases showed marked obliterative phlebitis. The IgG4 labeling index (LI) was 25% or more in all but one case. In the portion other than the mass, the lobular structure was well preserved and the IgG4 LI was less than 10%. The pancreatogram showed localized stenosis or obstruction at the site of the mass associated with a normal-appearing main pancreatic duct in the remaining portion. In group B, histological findings typical of chronic pancreatitis with dilated branch ducts and protein plugs were observed. Obliterative phlebitis was not confirmed. The IgG4 LI in the mass-forming portion was low (2.3%-11.1%).

CONCLUSIONS

There exists a subgroup of AIP showing localized mass formation and stenosis or obstruction of the main pancreatic duct with prominent obliterative phlebitis associated with a normal ductal segment.

Pathology of autoimmune pancreatitis and tumor-forming pancreatitis

The most frequently recognized presentation of autoimmune pancreatitis (AIP) is that mimicking pancreatic cancer. It is also known that at some stage during the disease process chronic pancreatitis clinically presents as a tumorous swelling, often suspected of being a carcinoma. In Japan, this stage has also been proposed clinically to be tumor-forming pancreatitis. Hence, tumor-forming pancreatitis shows at least two distinct types: a reparative process for centriductal acute inflammation with a background of chronic pancreatitis, which is considered to have given rise to the tumor at some stage of chronic pancreatitis, and a lymphoplasmacytic infiltration with lymphoid and fibrous proliferation in normal pancreatic tissue, which corresponds to autoimmune pancreatitis. These tumorous lesions may be changeable along the disease process.

Activated perilobular, not periacinar, pancreatic stellate cells contribute to fibrogenesis in chronic alcoholic pancreatitis

The authors investigated the role of activated perilobular, not periacinar, pancreatic stellate cells, in fibrogenesis in chronic pancreatitis, based on the distribution of myofibroblasts. Twenty-four patients with clinically diagnosed chronic alcoholic pancreatitis were studied histopathologically, immunohistochemically and quantitatively. In all cases, fibrosis was patchily distributed in the perilobular, or interlobular, areas, accompanied by a cirrhosis-like appearance; it had extended into the intralobular area in advanced cases. Seven patients had a massive or confluent loss of exocrine tissue, resulting in extensive interlobular fibrosis; the more extensive the interlobular fibrosis, the smaller the lobules. Immunoreactivity to alpha-smooth muscle actin, a myofibroblast marker, was found mostly in the same areas of the fibrosis, mainly the interlobular, and less often the periacinar, areas; the average percentage area of perilobular myofibroblasts was significantly higher than that of periacinar myofibroblasts in 20 randomly selected lobules (P > 0.001), in which the average value for the former was 38.03% (range: 13.54-61.32%; SD, 13.8%) and that for the latter was 4.85% (range 0.90-9.57%; SD, 2.22%). Fibrosis also immunostained positive for collagen types I and III. In conclusion, activated perilobular, not periacinar, pancreatic stellate cell contribute to fibrogenesis in chronic pancreatitis.

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.

Recurrent attacks of autoimmune pancreatitis result in pancreatic stone formation

OBJECTIVES

Autoimmune pancreatitis has been characterized by irregular narrowing of the main pancreatic duct and sonolucent swelling of the parenchyma, both of which are due to lymphoplasmacytic inflammation at the active stage of the disease, and by the absence of pancreatic stone formation. The aim of the present study was to confirm or deny whether or not this disease is progressive with recurrent attacks, resulting in pancreatic stone formation like ordinary chronic pancreatitis.

METHODS

Forty-two patients, 36 of whom were treated with prednisolone, were followed up for periods longer than 12 months (median follow-up period: 54.5 months, range: 13-111 months) by regular interview and examination of their medical records for laboratory tests and image tests.

RESULTS

Eleven patients (26.2%) who were treated with prednisolone showed recurrent attacks during median follow-up periods of 22 months. Eight patients (19%) showed the formation of pancreatic stones during the follow-up periods. Because 6 of 11 patients (54.5%) who suffered relapse showed pancreatic stone formation, it is significantly associated with relapse in comparison with nonrelapse (p= 0.0019).

CONCLUSIONS

Contrary to previous reports, we observed both relapse and pancreatic stone formation in some patients with autoimmune pancreatitis, which suggests that autoimmune pancreatitis has the potential to be a progressive disease with pancreatic stones.

Chronic pancreatitis. The problems of diagnostic criteria

The diagnostic criteria for chronic pancreatitis proposed by the Japan Pancreas Society (JPS) classified chronic pancreatitis into (i) definite; (ii) probable, and (iii) possible chronic pancreatitis, excluding obstructive, inflammatory (autoimmune) and tumor-forming pancreatitis from the definition of chronic pancreatitis. In the JPS Criteria, imaging studies, pancreatic function tests, and histological findings are independent of each other, and thus the diagnosis of chronic pancreatitis is made if one of the criteria is satisfied, regardless of the etiology of the chronic pancreatitis. The current diagnostic criteria for chronic pancreatitis depend on abnormalities of the duct system, such as low bicarbonate output, dilation of main pancreatic duct and duct branches, and calculi in the ducts by imaging studies. We revealed that the difference between reversible and irreversible pancreatitis in experimental animals is dependent on the degree of damage of the duct epithelium where pancreas progenitor cells exist. Thus, chronic pancreatitis diagnosed by the current criteria based on abnormalities of the duct system is irreversible. In contrast, the epithelium of the ducts is usually preserved in obstructive and autoimmune pancreatitis in that both structural and functional changes recover almost completely when the obstruction is removed or the inflammatory changes disappear following steroid administration. Even in chronic pancreatitis defined as irreversible, there must be a reversible stage during its clinical course. There is a need to develop biological markers and/or imaging procedure to detect chronic pancreatitis at its reversible stage.

Clinical and imaging features of autoimmune pancreatitis with focal pancreatic swelling or mass formation: comparison with so-called tumor-forming pancreatitis and pancreatic carcinoma

OBJECTIVES

Autoimmune pancreatitis (AIP) with a mass formation or swollen pancreas located in one or two segments of the gland (focal type AIP) has been reported. The aims of this study were to elucidate the relationship of the disease entity between this focal variant and so-called tumor-forming pancreatitis (TFP) and to describe the clinical and imaging features discriminating focal AIP from pancreatic carcinoma (Pca).

METHODS

The clinical, radiologic, and pathologic profiles of nine patients with focal AIP were reviewed retrospectively and compared with those of 11 patients with alcohol-induced TFP and 80 patients with Pca.

RESULTS

The patients with focal AIP were predominantly older (mean age 64.7 +/- 13.6 yr, range 28-78 yr), male, and presenting with obstructive jaundice or focal pancreatic enlargement accompanied by mild abdominal symptoms. In comparison, the patients with alcohol-induced TFP who were mostly middle-aged (mean age 50.1 +/- 7.95 yr, range 39-62 yr), male, and often had attacks of pancreatitis associated with findings of CT scans showing pseudocysts or peripancreatic effusion. Focal AIP usually demonstrated no abnormalities on pancreatograms downstream from the stricture or obstruction and often presented few contrast-filled side branches in the area of main pancreatic duct (MPD) stenosis. These characteristics were similar to the imaging features of Pca. Significant factors differentiating focal AIP from Pca were lower serum levels of CA19-9, homogeneous delayed enhancement evident in dynamic CT scans, and ERCP findings exhibiting a longer stenosed MPD and a thinner MPD upstream from the stricture.

CONCLUSIONS

Focal AIP is associated with clinical and radiologic features that are different from those of alcohol-induced TFP. In TFP there are two causative factors, namely, AIP and alcohol-induced chronic pancreatitis. Differential diagnosis of focal AIP from Pca seems to be possible in many cases by evaluating imaging findings such as dynamic CT and ERCP, although focal AIP sometimes shows clinical and radiologic features similar to those of Pca.

Clinical study of chronic pancreatitis with focal irregular narrowing of the main pancreatic duct and mass formation: comparison with chronic pancreatitis showing diffuse irregular narrowing of the main pancreatic duct

INTRODUCTION

Main pancreatic duct (MPD)-narrowed chronic pancreatitis (CP) may be an autoimmune abnormality. It also has been called autoimmune pancreatitis and sclerosing pancreatitis. It is unclear whether cases with focal pancreatographic changes are part of the same clinical entity as cases with diffuse MPD changes.

AIM AND METHODOLOGY

We reviewed seven cases of chronic pancreatitis (CP) with focal narrowing of the main pancreatic duct (MPD), evidenced by endoscopic retrograde cholangiopancreatography (ERCP), and swelling of one or two segments of the pancreas, evidenced by ultrasonography (US) /computed tomography (CT), and indicated the clinicopathologic features of focal-type MPD-narrowed CP.

RESULTS

The patient group comprised six men and one woman, and their age range was 28-75 years, with a mean of 63.7 years. Affected sites were in the head in two patients, the body in one patient, the tail in one patient, and the body and tail in three patients; ERP showed narrowing in six patients and obstruction in one. Stricture of the lower portion of the common bile duct (CBD) that caused obstructive jaundice was shown by ERC in two cases in which the pancreas head was affected. In all six patients, a dynamic study by CT or MRI homogeneously showed delayed enhancement of involved segments of the pancreas. Serum levels of pancreatic enzyme were elevated in five patients, but only one subject had pancreatitis-like epigastric pain. Serological evidence suggestive of autoimmune abnormality was detected in only three patients with hypergammaglobulinemia (> or =2.0 g/dL) or positive titers of antinuclear antibody (ANA; > or =80). Histological assessment was available for five patients, who characteristically had dense lymphocytic or plasmocytic infiltration with severe fibrosis that caused luminal narrowing. The clinical, serologic, and histologic findings as described above were comparable to those for 12 CP patients with diffuse narrowing of the MPD, diagnosed during the same period. Surgical resection was performed in 5 patients, in 2 of whom a similar inflammatory process recurred in the remnant head of the pancreas, whereas pancreatitis no longer developed in the other 3 patients. One patient was initially treated with steroids, with clinical remission, although there was neither hypergammaglobulinemia nor positive ANA.

CONCLUSION

These results indicate that CP with focal narrowing of the MPD is part of the same clinical spectrum as CP with diffuse narrowing of the MPD, and whether the distribution is diffuse or focal seems to be related to the stage or the extent of the disease. It is therefore important to recognize the possible existence of this focal variant to avoid unnecessary surgery.