The Pancreatic Duct and Its Arteriovenous Relationship

Evaluation of fine-needle core biopsy specimens for pancreatic ductal adenocarcinoma: Diagnostic utility and helpful histological features

AIMS

With the advent of new biopsy devices, fine-needle core biopsy specimens can be obtained from pancreas masses. This study aimed to report the histological spectrum of intrapancreatic adenocarcinoma on fine-needle core biopsy and the accuracy of sampling.

METHODS AND RESULTS

We identified 423 SharkCore™ fine-needle core biopsies taken from patients with a high clinical concern for pancreatic adenocarcinoma. For each, we recorded patient age and sex, percentage of diagnostic tissue in each sample and tumour site, size and histological findings. The cases came from 392 patients (193 men, 199 women; mean age 69 years). Median diagnostic tissue amount in the samples was 30%. Common histological findings included desmoplasia (36%), single atypical cells (44%), haphazard glandular growth pattern (68%), nuclear pleomorphism > 4:1 (39%), incomplete gland lumens (18%) and detached atypical epithelial strips (37%). Additional levels were ordered on 143 cases. Final clinical diagnoses associated with the 423 cases were adenocarcinoma (n = 343), pancreatitis (n = 22), intraductal neoplasm or other benign/low-grade process (n = 16) and unknown (n = 42, patients lost to follow-up). Of the adenocarcinoma cases, the diagnosis was established by the evaluated fine-needle core biopsy sample alone in 178, by fine-needle aspiration biopsy alone in 30, by both concurrently in 89 and by subsequent biopsy or resection in 37 cases. Among 68 cases called suspicious on fine-needle core biopsy, 78% ultimately represented adenocarcinoma.

CONCLUSIONS

Fine-needle core biopsy allows for histological diagnosis of pancreatic adenocarcinoma, using known histological parameters. Common findings include single atypical cells, desmoplasia, haphazard gland growth and nuclear pleomorphism. Cases interpreted as suspicious often represent malignancy.

Tissue clearing and 3D reconstruction of digitized, serially sectioned slides provide novel insights into pancreatic cancer

Pancreatic cancer is currently the third leading cause of cancer death in the United States. The clinical hallmarks of this disease include abdominal pain that radiates to the back, the presence of a hypoenhancing intrapancreatic lesion on imaging, and widespread liver metastases. Technologies such as tissue clearing and three-dimensional (3D) reconstruction of digitized serially sectioned hematoxylin and eosin-stained slides can be used to visualize large (up to 2- to 3-centimeter cube) tissues at cellular resolution. When applied to human pancreatic cancers, these 3D visualization techniques have provided novel insights into the basis of a number of the clinical characteristics of this disease. Here, we describe the clinical features of pancreatic cancer, review techniques for clearing and the 3D reconstruction of digitized microscope slides, and provide examples that illustrate how 3D visualization of human pancreatic cancer at the microscopic level has revealed features not apparent in 2D microscopy and, in so doing, has closed the gap between bench and bedside. Compared with animal models and 2D microscopy, studies of human tissues in 3D can reveal the difference between what can happen and what does happen in human cancers.

Pancreatic duct ligation reduces premalignant pancreatic lesions in a Kras model of pancreatic adenocarcinoma in mice

Pancreatic duct ligation (PDL) in the murine model has been described as an exocrine pancreatic atrophy-inducing procedure. However, its influence has scarcely been described on premalignant lesions. This study describes the histological changes of premalignant lesions and the gene expression in a well-defined model of pancreatic ductal adenocarcinoma by PDL. Selective ligation of the splenic lobe of the pancreas was performed in Ptf1a-Cre^(+/ki); K-ras LSLG12Vgeo^(+/ki) mice (PDL-Kras mice). Three experimental groups were evaluated: PDL group, controls and shams. The presence and number of premalignant lesions (PanIN 1–3 and Atypical Flat Lesions—AFL) in proximal (PP) and distal (DP) pancreas were studied for each group over time. Microarray analysis was performed to find differentially expressed genes (DEG) between PP and PD. Clinical human specimens after pancreaticoduodenectomy with ductal occlusion were also evaluated. PDL-Kras mice showed an intense pattern of atrophy in DP which was shrunk to a minimal portion of tissue. Mice in control and sham groups had a 7 and 10-time increase respectively of risk of high-grade PanIN 2 and 3 and AFL in their DP than PDL-Kras mice. Furthermore, PDL-Kras mice had significantly less PanIN 1 and 2 and AFL lesions in DP compared to PP. We identified 38 DEGs comparing PP and PD. Among them, several mapped to protein secretion and digestion while others such as Nupr1 have been previously associated with PanIN and PDAC. PDL in Ptf1a-Cre^(+/ki); K-ras LSLG12Vgeo^(+/ki) mice induces a decrease in the presence of premalignant lesions in the ligated DP. This could be a potential line of research of interest in some cancerous risk patients.

Three-dimensional visualization of cleared human pancreas cancer reveals that sustained epithelial-to-mesenchymal transition is not required for venous invasion

Venous invasion is three times more common in pancreatic cancer than it is in other major cancers of the gastrointestinal tract, and venous invasion may explain why pancreatic cancer is so deadly. To characterize the patterns of venous invasion in pancreatic cancer, 52 thick slabs (up to 5 mm) of tissue were harvested from 52 surgically resected human ductal adenocarcinomas, cleared with a modified iDISCO method, and labeled with fluorescent-conjugated antibodies to cytokeratin 19, desmin, CD31, p53 and/or e-cadherin. Labeled three-dimensional (3D) pancreas cancer tissues were visualized with confocal laser scanning or light sheet microscopy. Multiple foci of venous and even arterial invasion were visualized. Venous invasion was detected more often in 3D (88%, 30/34 cases) than in conventional 2D slide evaluation (75%, 25/34 cases, P < 0.001). 3D visualization revealed pancreatic cancer cells crossing the walls of veins at multiple points, often at points where preexisting capillary structures bridge the blood vessels. The neoplastic cells often retained a ductal morphology (cohesive cells forming tubes) as they progressed from a stromal to intravenous location. Although immunolabeling with antibodies to e-cadherin revealed focal loss of expression at the leading edges of the cancers, the neoplastic cells within veins expressed e-cadherin and formed well-oriented glands. We conclude that venous invasion is almost universal in pancreatic cancer, suggesting that even surgically resectable PDAC has access to the venous spaces and thus the ability to disseminate widely. Furthermore, we observe that sustained epithelial-mesenchymal transition is not required for venous invasion in pancreatic cancer.

Pancreatic Ductal Adenocarcinoma and Its Precursor Lesions: Histopathology, Cytopathology, and Molecular Pathology

Pancreatic ductal adenocarcinoma is one of the most aggressive malignant neoplasms with poor outcomes. At the time of diagnosis, the disease is usually at an advanced stage and only a minority is eligible for surgical resection. To improve the prognosis, it is essential to diagnose and treat the disease in an early stage before its progression into an invasive disease. This article reviews clinical features, histopathology, cytopathology, and molecular alterations of pancreatic ductal adenocarcinoma and its precursors. Moreover, we review a recently updated two-tier classification system for precursor lesions, new findings in premalignant cystic neoplasms, and recently updated staging criteria for invasive carcinoma based on the Cancer Staging Manual, eighth edition, from the American Joint Committee on Cancer. Finally, we discuss the potential clinical applications of the rapidly growing molecular and genetic information of pancreatic cancer and its precursors.

A "Clearer" View of Pancreatic Pathology: A Review of Tissue Clearing and Advanced Microscopy Techniques

Although pathologic lesions in the pancreas are 3-dimensional (3D) complex structures, we currently use thin 2D hematoxylin and eosin stained slides to study and diagnose pancreatic pathology. Two technologies, tissue clearing and advanced microscopy, have recently converged, and when used together they open the remarkable world of 3D anatomy and pathology to pathologists. Advances in tissue clearing and antibody penetration now make even dense fibrotic tissues amenable to clearing, and light sheet and confocal microscopies allow labeled cells deep within these cleared tissues to be visualized. Clearing techniques can be categorized as solvent-based or aqueous-based techniques, but both clearing methods consist of 4 fundamental steps, including pretreatment of specimens, permeabilization and/or removal of lipid, immunolabeling with antibody penetration, and clearing by refractive index matching. Specialized microscopes, including the light sheet microscope, the 2-photon microscope, and the confocal microscope, can then be used to visualize and evaluate the 3D histology. Both endocrine and exocrine pancreas pathology can then be visualized. The application of labeling and clearing to surgically resected human pancreatic parenchyma can provide detailed visualization of the complexities of normal pancreatic anatomy. It also can be used to characterize the 3D architecture of disease processes ranging from precursor lesions, such as pancreatic intraepithelial neoplasia lesions and intraductal papillary mucinous neoplasms, to infiltrating pancreatic ductal adenocarcinomas. The evaluation of 3D histopathology, including pathology of the pancreatic lesions, will provide new insights into lesions that previously were seen, and thought of, only in 2 dimensions.

Immunolabeling of Cleared Human Pancreata Provides Insights into Three-Dimensional Pancreatic Anatomy and Pathology

Visualizing pathologies in three dimensions can provide unique insights into the biology of human diseases. A rapid and easy-to-implement dibenzyl ether-based technique was used to clear thick sections of surgically resected human pancreatic parenchyma. Protocols were applicable to both fresh and formalin-fixed, paraffin-embedded tissue. The penetration of antibodies into dense pancreatic parenchyma was optimized using both gradually increasing antibody concentrations and centrifugal flow. Immunolabeling with antibodies against cytokeratin 19 was visualized using both light sheet and confocal laser scanning microscopy. The technique was applied successfully to 26 sections of pancreas, providing three-dimensional (3D) images of normal pancreatic tissue, pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasms, and infiltrating pancreatic ductal adenocarcinomas. 3D visualization highlighted processes that are hard to conceptualize in two dimensions, such as invasive carcinoma growing into what appeared to be pre-existing pancreatic ducts and within venules, and the tracking of long cords of neoplastic cells parallel to blood vessels. Expanding this technique to formalin-fixed, paraffin-embedded tissue opens pathology archives to 3D visualization of unique biosamples and rare diseases. The application of immunolabeling and clearing to human pancreatic parenchyma provides detailed visualization of normal pancreatic anatomy, and can be used to characterize the 3D architecture of diseases including pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and pancreatic ductal adenocarcinomas.

Novel agents for advanced pancreatic cancer

Pancreatic cancer is relatively insensitive to conventional chemotherapy. Therefore, novel agents targeting dysregulated pathways (MAPK/ERK, EGFR, TGF-β, HEDGEHOG, NOTCH, IGF, PARP, PI3K/AKT, RAS, and Src) are being explored in clinical trials as monotherapy or in combination with cytotoxic chemotherapy. This review summarizes the most recent advances with the targeted therapies in the treatment of patients with advanced pancreatic cancer.

Difficult Diagnostic Problems in Pancreatobiliary Neoplasia

CONTEXT

Many common diagnostic dilemmas are encountered in pancreatobiliary pathology, frequently resulting in uncertainty on behalf of the pathologist and referral for a second opinion.

OBJECTIVES

To review 4 common diagnostic dilemmas encountered in the practice of pancreatobiliary pathology: (1) pancreatic ductal adenocarcinoma versus chronic pancreatitis; (2) pancreatic ductal carcinoma versus adenocarcinomas arising in the ampulla and intrapancreatic common bile duct; (3) the distinction of uncommon intraductal neoplasms--intraductal oncocytic papillary neoplasm, intraductal tubulopapillary neoplasm, and intraductal acinar cell carcinoma; and (4) intrahepatic cholangiocarcinoma versus metastatic carcinoma.

DATA SOURCES

A review of pertinent literature, along with the authors' personal experience, based on institutional and consultation materials.

CONCLUSIONS

Important diagnostic features for a few challenging problems in pancreatobiliary pathology are reviewed. Careful study of the microscopic features along with awareness of differential diagnoses and diagnostic pitfalls generally allows distinction of these entities. We also highlight established and novel ancillary studies that help to arrive at an accurate diagnosis.

Adenocarcinoma of the pancreas

Infiltrating ductal adenocarcinoma of the pancreas is a real enigma. On one hand, it is one of the most deadly of all of the solid malignancies. On the other hand, the neoplastic glands can be remarkably well-differentiated, and it can be difficult to distinguish between a reactive non-neoplastic gland and a gland of invasive adenocarcinoma. In this review, we will present diagnostic criteria that one can "hang your hat on" when establishing the diagnosis of infiltrating ductal adenocarcinoma of the pancreas. We will also review clinically important features of the disease, and, with the impending incorporation of molecular genetics into everyday practice, we will emphasize clinical applications of cancer genetics.

Pancreatic intraepithelial neoplasia in the background of invasive ductal carcinoma of the pancreas as a prognostic factor

AIMS

Of the recognized precursor lesions of pancreatic adenocarcinoma, pancreatic intraepithelial neoplasia (PanIN) is the most common form. However, little is known about the relationship between the grade of PanIN and prognosis for patients with invasive ductal carcinoma.

METHODS AND RESULTS

In 124 patients with invasive ductal carcinoma, we examined the grade and number of PanIN lesions in all slides of resected pancreas. The prevalence rates of PanIN-1A, PanIN-1B, PanIN-2 and PanIN-3 were 86%, 84%, 57% and 30%, respectively. We allocated PanIN-2 and PanIN-3 cases into a PanIN-high group, and cases showing PanIN-1A, PanIN-1B or absence of PanIN into a PanIN-low group. In clinicopathological analysis, PanIN-high status was significantly correlated with the number of PanIN lesions (P < 0.0001). Disease-free and overall survival were statistically better in the PanIN-high group than in the PanIN-low group (P = 0.0005 and P = 0.0003). Univariate and multivariate analyses revealed that tumour size and PanIN-low status were statistically significant factors for a poorer prognosis (P = 0.042 and P = 0.007).

CONCLUSIONS

In a pathological examination, it is important to evaluate the grade and number of PanINs in assessing the prognosis of pancreatic cancer.

Aberrant signaling pathways in pancreatic cancer: a two compartment view

Pancreatic cancer is a devastating disease with historically limited success in treatment and a poor prognosis. Pancreatic cancer appears to have a progressive pathway of development, initiating from well-described pancreatic intraepithelial neoplasia lesions and concluding with invasive carcinoma. These early lesions have been shown to harbor-specific alterations in signaling pathways that remain throughout this tumorigenesis process. Meanwhile, new alterations occur during this process of disease progression to have a cumulative effect. This series of events not only impacts the epithelial cells comprising the tumor, but they may also affect the surrounding stromal cells. The result is the formation of complex signaling networks of communication between the tumor epithelial cell and the stromal cell compartments to promote a permissive and cooperative environment. This article highlights some of the most common pathway aberrations involved with this disease, and how these may subsequently affect one or both cellular compartments. Consequently, furthering our understanding of these pathways in terms of their function on the tumoral epithelial and stromal compartments may prove to be crucial to the development of targeted and more successful therapies in the future.

Pancreatic Intraepithelial Neoplasia

Pancreatic intraepithelial neoplasias (PanINs) are microscopic lesions of the pancreas. Traditionally viewed as a benign metaplasia of small ducts, evidence suggests that PanINs are neoplastic and that some PanINs progress to invasive ductal adenocarcinoma. The primary diagnostic challenge is distinguishing PanINs from other lesions, including invasive ductal adenocarcinoma, intraductal papillary mucinous neoplasm, and cancerization of benign ducts. PanINs are the most common of the pancreatic cancer precursor lesions, yet they remain poorly understood and are so small that they are almost clinically undetectable. Further study is required to define the role of PanINs in the carcinogenesis and early detection of pancreatic cancer.

Italian consensus guidelines for chronic pancreatitis

This paper gives practical guidelines for diagnosis and treatment of chronic pancreatitis. Statements have been elaborated by working teams of experts, by searching for and analysing the literature, and submitted to a consensus process by using a Delphi modified procedure. The statements report recommendations on clinical and nutritional approach, assessment of pancreatic function, treatment of exocrine pancreatic failure and of secondary diabetes, treatment of pain and prevention of painful relapses. Moreover, the role of endoscopy in approaching pancreatic pain, pancreatic stones, duct narrowing and dilation, and complications was considered. Recommendations for most appropriate use of various imaging techniques and of ultrasound endoscopy are reported. Finally, a group of recommendations are addressed to the surgical treatment, with definition of right indications, timing, most appropriate procedures and techniques in different clinical conditions and targets, and clinical and functional outcomes following surgery.

Isolated solitary ducts (naked ducts) in adipose tissue: a specific but underappreciated finding of pancreatic adenocarcinoma and one of the potential reasons of understaging and high recurrence rate

The distinction of ductal adenocarcinoma from chronic pancreatitis remains one of the most difficult challenges in surgical pathology. The glandular units of invasive carcinoma are often well formed with well-polarized cells, appearing deceptively benign. Conversely, the ducts of chronic pancreatitis may be atypical and pseudoinfiltrative as a result of acinar atrophy and fibrosis. We recently noted isolated solitary ductal units (ISDs) in adipose tissue to be a reliable indicator of adenocarcinoma. In this study, the frequency of ISDs was investigated in 105 pancreatic resections with ductal adenocarcinoma and 32 with chronic pancreatitis only. ISD was defined as a solitary gland lying individually in adipose tissue, either directly abutting adipocytes or separated from them by only a thin rim of fibromuscular tissue. ISD was detected in 50/105 (47.6%) of pancreatic resections for ductal adenocarcinoma, but not in any resections with chronic pancreatitis only (specificity 100%; sensitivity 47.6%). Most of the ISDs were very well differentiated and cytologically bland. A small subset of these units represented vascular invasion, in which the carcinoma cells epithelialized the vessel lining, transforming the vessel into a duct-like structure, virtually indistinguishable from normal ducts or PanINs. The vascular nature of these units was verified by Elastic-Van Gieson stain and muscular markers highlighting the elastic lamina and muscular wall, respectively. ISDs were often located in histologic sections taken for the evaluation of the retroperitoneal margin and pancreatic-free surfaces where adipose tissue is more abundant. In conclusion, ISD lying in adipose tissue unaccompanied by other elements, present in 47.6% of pancreatic resections when peripancreatic soft tissues away from the tumor are sampled, is a very specific finding for carcinoma that may be instrumental in the diagnosis and staging of carcinoma as well as margin evaluation.

Chronic Pancreatitis and the Differential Diagnosis Versus Pancreatic Cancer

Context.—Distinguishing chronic pancreatitis from pancreatic ductal adenocarcinoma (PDAC) is a well-known challenge, at both the clinical and the morphologic level.

Objective.—To focus on the histopathologic findings that are diagnostic or suggestive of PDAC.

Data Sources.—Findings that are specific to PDAC are the presence of duct structures in perineural and vascular spaces and (“naked”) ducts in fatty tissue. However, these findings are only observed in specimens containing extrapancreatic tissue. The features that are suggestive of PDAC in specimens from the pancreas include haphazard distribution of ductlike structures (ie, loss of a lobular pattern), markedly irregular ductal contours, ruptured ducts, nuclear enlargement, pleomorphism and hyperchromatism, and mitotic figures. Immunohistologic markers that are helpful are carcinoembryonic antigen, MUC1, p53, and Ki-67/ MIB1.

Conclusions.—There are a few features that are diagnostic and a number that are suggestive of PDAC. Therefore, a combination of several features may be required to clearly distinguish chronic pancreatitis from invasive PDAC.

Pancreatic cancer microenvironment

Pancreatic ductal adenocarcinoma remains an extremely aggressive malignancy that is virtually therapy-resistant and has therefore one of the worst prognoses of all human cancers. The focus of research, which had been placed mostly on genetic and epigenetic alterations of the cancer cells themselves, has shifted gradually towards the microenvironment. The cancer microenvironment consists of various components, including fibroblasts, endothelial cells, immune cells, and endocrine cells, that interact with each other and the cancer cells in a complex fashion. This interplay has implications for pancreatic cancer cell growth, migration and invasion, angiogenesis, and immunological recognition of cancer cells. Evidence is accumulating that the cancer microenvironment plays an active role in disease progression, and efforts are being made to target this interplay between cancer cells and host cells to improve the outcome of this deadly disease.

Intraoperative assessment of the Whipple resection specimen

Intraoperative consultation for the Whipple resection procedure has evolved due to the increasing influence of imaging techniques in surgical planning and decision-making. The indications and utilisation of this service vary, at least to some degree, from one institution to the other. The following discussion is a single institutional approach, which is hoped to provide assistance to the practising pathologists in this field. Special emphasis is given to the relevant anatomical considerations and the most common indications for an intraoperative consultation.

Pancreatic adenocarcinoma: update on the surgical pathology of carcinomas of ductal origin and PanINs

Pancreatic cancer is the fourth leading cause of cancer death in the US. Most pancreatic cancers are infiltrating ductal adenocarcinomas. The careful application of well-defined morphologic criteria can be used to differentiate between infiltrating ductal adenocarcinoma and reactive glands. While most pancreatic cancers are ductal adenocarcinomas, a number of histologically defined variants have been described. These are important to recognize because they have distinct clinical pathologic features. Pancreatic intraepithelial neoplasia (PanIN) is the presumed precursor lesion to infiltrating ductal adenocarcinoma, and PanIN lesions can mimic infiltrating cancer.

Cytokeratin 20 expression identifies a subtype of pancreatic adenocarcinoma with decreased overall survival

BACKGROUND

Cytokeratins are markers of epithelial cell differentiation useful in determining histogenesis for malignancies with an unknown primary. Application of this principle to a single malignancy may identify cancer subtypes with altered developmental programs. Herein, we investigate the relevance of two widely used cytokeratins (CKs), 7 and 20, to subtype pancreas cancer and identify associations with clinical features.

METHODS

A tissue microarray was constructed using tumor specimens from 103 patients who underwent resection for pancreatic adenocarcinoma with curative intent. A subset of resection specimens was evaluated for pancreatic intraepithelial neoplasia (PanIN) lesions. Tissues were immunostained by using specific anticytokeratin 7 and 20 monoclonal antibodies.

RESULTS

CK 7 and 20 expression was present in 96% and 63% cases of pancreatic adenocarcinoma, respectively. Ubiquitous CK 7 expression precluded further analysis. Tumoral CK 20 expression was not associated with any histopathologic parameter but correlated with worse prognosis when considered as either a dichotomous (P=0.0098) or continuous (P=0.007) variable. In a multivariate model, tumoral CK 20 expression remained a significant independent prognosticator. CK 20 expression was absent in all PanIN lesions from eight resection specimens in which the tumor component was negative for CK 20. In contrast, presence of tumoral CK 20 was highly concordant with its expression in corresponding PanINs.

CONCLUSIONS

CK 20 expression defines a subtype of pancreas cancer with important biologic properties. When present, CK 20 expression is an early event in pancreatic carcinogenesis identifiable in precursor lesions. Further studies to identify the underlying genetic changes associated with this altered developmental pathway are warranted.

Chronic pancreatitis or pancreatic ductal adenocarcinoma?

The histopathologic distinction of ductal adenocarcinoma (DA) of the pancreas from chronic pancreatitis (CP) is a well-known challenge. Several parameters have been determined by the authors and other investigators to be useful in this distinction. The findings that are entirely diagnostic for DA are perineural and vascular invasion; however, they are rarely detectable in biopsy specimens. The most common findings that are highly suggestive of DC and can also be expected in biopsy specimens include random distribution of ductal structures, irregular ductal contours, nuclear enlargement (>3 times the size of a lymphocyte), and pleomorphism, distinct nucleoli, and mitosis. Other, somewhat rarer findings are uninterrupted proliferation of numerous (>50) ducts, intraluminal necrotic cellular debris, hyperchromatic raisinoid nucleoli, the presence of naked ducts in fat without surrounding pancreatic elements or fibrous tissue, and ducts lying adjacent to arterioles. Findings that favor a benign process over an invasive carcinoma are: lobular architecture with clusters of evenly spaced ductal units, uniformly sized ductal elements, smooth ductal contours, ducts surrounded by acini or islets, and intraluminal mucoprotein plugs. Combinations of these criteria should aid in the differential diagnosis of invasive ductal adenocarcinoma from benign/reactive ducts in the pancreas.

Focal Changes of Chronic Pancreatitis and Duct-Arteriovenous Relationships

A prior study of pancreatic duct-arteriovenous relationships suggested that finding ducts near muscularized blood vessels without intervening pancreatic acini indicated adenocarcinoma was present. Because focal changes of chronic pancreatitis are often seen at autopsy, it seemed reasonable to use the autopsy to test the hypothesis that this finding might be nonspecific. An unselected, consecutive series of 81 adult decedent pancreases without known pancreas cancer was evaluated for the presence of ducts near muscularized blood vessels, for fibrosis and/or atrophy, for chronic inflammation, and for duct reduplication and/or proliferation. Autolysis precluded assessment of 26% of the cases. Of evaluable cases, 37% displayed ducts near muscularized blood vessels without intervening pancreatic acini, 23% chronic inflammation, 62% fibrosis and/or atrophy, and 55% duct reduplication and/or proliferation. The finding of ducts near muscularized blood vessels was closely associated with fibrosis and/or atrophy (odds ratio = 28.87, chi = 14.59, P = 0.0001), with duct reduplication and/or proliferation (odds ratio = 19.23, chi = 15.88, P = 0.0001), but not with chronic inflammation (odds ratio = 1.41, chi = 0.05, P > 0.30). Because changes of chronic pancreatitis are associated with ducts near muscularized blood vessels and because chronic pancreatitis can mimic pancreas cancer, care should be exercised when using the finding of ducts near muscularized blood vessels without intervening pancreatic acini as a criterion for the diagnosis of pancreas cancer.

Precursors to invasive pancreatic cancer

Pancreatic cancer, once invasive, is almost uniformly fatal. In order to alleviate the dismal prognosis associated with this disease, it is imperative that pancreatic cancer be recognized and treated prior to invasion. Understanding the morphology and biology of precursor lesions of invasive pancreatic cancer has therefore become an issue of paramount importance. In the last decade, significant progress has been in the recognition and appropriate classification of these precursor lesions, and the current review will focus on our state-of-the-art knowledge on this topic. Mucinous cystic neoplasms (MCNs), intraductal papillary mucinous neoplasms (IPMNs), and pancreatic intraepithelial neoplasia (PanIN) encompass the three known morphologically distinct precursors to invasive pancreatic cancer. In addition to discussion of the "classic" precursor entities, this review will also address some of the recent diagnostic controversies for these lesions, in particular features that distinguish IPMNs from PanIN lesions. Finally, the potential clinical impact of recognizing these precursor lesions in the context of early detection of pancreatic cancer will be discussed.