Classification of types of intraductal papillary-mucinous neoplasm of the pancreas: a consensus study

Tumor immune microenvironment alterations associated with progression in human intraductal papillary mucinous neoplasms

Pancreatic ductal adenocarcinoma (PDAC) poses a significant challenge due to late-stage diagnoses. To improve patient outcomes, early intervention in precursor lesions such as intraductal papillary mucinous neoplasm (IPMN) is crucial. However, early intervention must be balanced against overtreatment of low-risk lesions that are unlikely to progress, underscoring the need to better understand molecular alterations in neoplastic cells and changes in the tumor microenvironment (TME) that drive the progression of IPMNs. In this study, we characterized alterations in the TME of IPMNs as they progressed to high-grade dysplasia, using immunohistochemistry to quantify immune cell density and activation status in more than 100 well-characterized human IPMN samples. Analyses revealed progression to a more immunosuppressive TME in high-grade IPMN compared with low-grade IPMN, characterized by elevated expression of immune checkpoint molecules (PD-L1, TIM3, VISTA), increased density of macrophages, and decreased density of cytotoxic T cells. Intriguingly, the alterations in macrophages were limited to focal regions of high-grade dysplasia, while T-cell alterations affected the entire IPMN. Additionally, elevated VISTA expression was associated with poorer clinical outcome after IPMN resection in an independent cohort. These findings provide important insights into the interplay between the immune microenvironment and IPMN progression, highlighting potential targets to modify the TME for cancer interception. © 2025 The Pathological Society of Great Britain and Ireland.

Clinical impact of epithelial types on postoperative outcomes for intraductal papillary mucinous neoplasms: a multicenter retrospective study

BACKGROUND

Intraductal papillary mucinous neoplasms (IPMNs) are classified into three epithelial types with distinct biological behaviors. However, their effects on the postoperative outcomes remain unclear.

METHODS

This multicenter retrospective study included 556 patients with IPMNs who underwent surgical resection. The epithelial types were categorized into the gastric (n = 323), intestinal (n = 160), and pancreatobiliary (n = 73) types. Their associations with the development of extrapancreatic lesions; remnant high-risk lesions (HRLs), including metachronous pancreatic ductal adenocarcinoma (PDAC); and disease-specific survival (DSS) were analyzed.

RESULTS

Fifty-one patients (9.2%) developed extrapancreatic lesions. The 10-year cumulative incidence rates for the gastric, intestinal, and pancreatobiliary types were 9.3%, 9.1%, and 32.0%, respectively (P < 0.001). Multivariate analysis identified invasive carcinoma, the gastric, and pancreatobiliary types as independent predictors. Among 516 patients who did not undergo total pancreatectomy, 40 (7.8%) and 13 (2.5%) developed HRLs and metachronous PDAC, respectively. The 10-year cumulative incidence rates of HRLs and metachronous PDAC for the gastric, intestinal, and pancreatobiliary types were 7.0%, 16.2%, and 37.2% and 1.8%, 3.7%, and 22.7%, respectively (P = 0.001 and P = 0.012). In multivariate analysis, the pancreatobiliary type was an independent predictor of metachronous PDAC. Five-year DSS rates for the gastric, intestinal, and pancreatobiliary types were 92.5%, 96.0%, and 76.1% (P < 0.001), respectively. Multivariate analysis identified invasive carcinoma, the gastric, and pancreatobiliary types as independent prognostic factors for DSS.

CONCLUSIONS

IPMN epithelial type can independently affect postoperative outcomes. In particular, the pancreatobiliary type has significant impact on the development of metachronous PDAC. Therefore, postoperative surveillance should be tailored according to the epithelial type.

[Precancerous lesions of the pancreas, prophylactic surgery]

Pancreatic cancer is a serious pathology whose incidence is increasing. Advances in imaging have made it possible to fortuitously highlight more and more cystic pancreatic lesions, some of which have a malignant potential, leading to the consideration of prophylactic excision. The various known precancerous lesions of the pancreas as well as current management recommendations are here reviewed.

Distinct prognostic impacts of age-adjusted Charlson comorbidity index and geriatric nutritional risk index in patients with intraductal papillary mucinous neoplasm

The optimal surgical indication for intraductal papillary mucinous neoplasms (IPMN) remains highly contentious. We aimed to determine the preoperative predictive factors of malignancy and independent prognostic factors in patients with IPMN who underwent curative-intent resection. In this study, 104 patients with a pathological diagnosis of IPMN who underwent curative-intent resection were included. Multivariate regression and Cox proportional-hazards analyses were performed to identify the predictive factors for invasive intraductal papillary mucinous carcinoma (IPMC) and prognostic factors for overall survival (OS) after surgery. Among the 104 patients, 24 (23.1%) were pathologically diagnosed with invasive IPMC, and the remaining 80 had low-grade dysplasia or high-grade dysplasia. The presence of high-risk stigmata was an independent predictive risk factor for invasive IPMC. The age-adjusted Charlson comorbidity index (ACCI) (≥4/<4) and geriatric nutritional risk index (GNRI) (<99/≥99) were independent poor prognostic factors for OS (hazard ratio [HR]: 9.39; 95% confidence interval [CI]: 1.90-46.54; P = .006 and HR: 4.37; 95% CI: 1.07-17.86, P = .040, respectively). Forty patients with ACCI ≥ 4 (38.5%) had a significantly lower 5-year OS rate than those with ACCI < 4 (74.3 vs 98.2%, P < .001). Similarly, 29 patients with GNRI < 99 (27.9%) had a significantly lower 5-year OS rate than those with GNRI ≥ 99 (76.0 vs 95.1%, P < .001). These 2 factors were associated with significantly worse disease-specific survival after surgery. The ACCI and GNRI emerged as independent prognostic factors after surgery in patients with IPMN. These findings highlight the importance of patient-conditional factors as valuable indicators for predicting favorable long-term survival outcomes after surgery and for facilitating a more precise assessment of surgical eligibility in patients with IPMN.

Histological Subtypes Might Help Risk Stratification in Different Morphological Types of IPMNs: Back to the Future?

Background: Intraductal papillary mucinous neoplasms (IPMNs) display four histological subtypes: gastric foveolar, pancreaticobiliary, intestinal, and oncocytic. All of these subtypes harbor a different risk of cancer development. The clinical impact of these subtypes concerning the occurrence of high-grade dysplasia (HGD)/cancer (C) in specific morphological types, such as branch-duct (BD), main-duct (MD), and mixed-type (MT) IPMNs, has been less investigated. Hence, our aim was to investigate the prevalence of histological subtypes and their possible association with HGD/C concerning morphologically different IPMNs. Methods: This was a retrospective review of demographics, risk factors, and histological features in a surgical cohort of patients having undergone resection for suspect malignant IPMNs at a high-volume tertiary center from 2007 to 2017. Results: A total of 273 patients were resected for IPMNs from during the study period, of which 188 were included in the final analysis. With sex- and age-adjusted multivariable logistic regression analysis across the entire cohort, gastric foveolar subtypes were associated with a reduced prevalence of HGD/C (OR = 0.30; 0.11-0.81, 95% CI, 95%CI; p = 0.01). With univariable logistic regression analysis, in the BD-IPMN subgroup, the pancreaticobiliary subtype was associated with an increased prevalence of HGD/C (OR = 18.50, 1.03-329.65, 95% CI; p = 0.04). In MD- and MT-IPMNs, the gastric foveolar subtype was associated with a decreased prevalence of HGD/cancer (OR = 0.30, 0.13-0.69, 95% CI; p = 0.004). Conclusions: In MD and MT-IPMNs, the gastric-foveolar subtype is associated with a lower prevalence of HGD/C, possibly identifying in such a high-risk group, a subgroup with more indolent behavior. In BD-IPMNs, the pancreaticobiliary subtype is associated with a higher prevalence of HGD/C, conversely identifying among those patients, a subgroup deserving special attention.

Neoplastic Progression in Macroscopic Precursor Lesions of the Pancreas

CONTEXT.—

Macroscopic precursor lesions of the pancreas represent a complex clinical management problem. Molecular characterization of pancreatic cysts has helped to confirm and refine clinical and pathologic classifications of these lesions, inform our understanding of tumorigenesis in the pancreas, and provide opportunities for preoperative diagnosis.

OBJECTIVE.—

To review the pathologic classification of macroscopic cystic lesions of the pancreas: intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCNs), intraductal oncocytic papillary neoplasms (IOPNs), and intraductal tubulopapillary neoplasms (ITPNs), and to describe our current state of understanding of their molecular underpinnings, relationship to invasive carcinomas, and implications for diagnosis and prognostication.

DATA SOURCES.—

We assessed the current primary literature and current World Health Organization Classification of Digestive System Tumours.

CONCLUSIONS.—

Macroscopic cystic lesions of the pancreas are morphologically and molecularly diverse. IPMNs and MCNs share mucinous cytoplasm with papillae. MCNs are defined by ovarian-type stroma. IOPNs have granular eosinophilic cytoplasm, prominent nucleoli, and complex, arborizing papillae. ITPNs demonstrate complex, back-to-back tubules and anastomosing papillae and lack prominent intracellular mucin. IPMNs and MCNs are characterized by driver mutations in KRAS/GNAS (IPMNs) and KRAS (MCNs), with later driver events in RNF43, CDKN2A, SMAD4, and TP53. In contrast, IOPNs and ITPNs have recurrent rearrangements in PRKACA/PRKACB and MAPK-associated genes, respectively. The recurrent alterations described in cysts provide an opportunity for diagnosis using aspirated cyst fluid. Molecular characterization of IPMNs shows a striking spatial and mutational heterogeneity, challenging traditional models of neoplastic development and creating challenges to interpretation of cyst fluid sequencing results.

Comprehensive Characterization of Intraductal Oncocytic Papillary Neoplasm of the Pancreas: A Systematic and Critical Review

Intraductal oncocytic papillary neoplasm (IOPN) of the pancreas is a recently recognized pancreatic tumor. Here, we aimed to determine its most essential features with the systematic review tool. PubMed, Scopus, and Embase were searched for studies reporting data on pancreatic IOPN. The clinicopathologic, immunohistochemical, and molecular data were extracted and summarized. Then, a comparative analysis of the molecular alterations of IOPN with those of pancreatic ductal adenocarcinoma and intraductal papillary mucinous neoplasm from reference cohorts (including The Cancer Genome Atlas) was conducted. The key findings from 414 IOPNs were as follows: 1) The male-to-female ratio was 1.5:1. Pancreatic head was the most common site (131/237; 55.3%), but a diffuse tumor extension involving more than one pancreatic segment was described in about 1 out of 5 cases (49/237; 20.6%). The mean size was 45.5 mm. An associated invasive carcinoma was present in 50% of cases (168/336). In those cases, most tumors were pT1 or pT2 and pN0 (>80%), and vascular invasion was uncommon (20.6%). Regarding survival, more than 90% of patients were alive after surgical resection. 2) Immunohistochemical and molecular features were as follows. The most commonly expressed mucins were MUC5AC (110/112; 98.2%) and MUC6 (78/84; 92.8%). Compared with pancreatic ductal adenocarcinoma and intraductal papillary mucinous neoplasm, the classic pancreatic drivers KRAS, TP53, CDKN2A, SMAD4, and GNAS were less altered in IOPN (P < .01). Moreover, fusions involving PRKACA or PRKACB gene were detected in all of the 68 cases examined, with PRKACB::ATP1B1 being the most common (27/68 cases; 39.7%). These genomic events emerged as an entity-defining molecular alteration of IOPN (P < .01). Thus, such fusions represent a promising biomarker for diagnostic purposes. Recent evidence also suggests their role in influencing the acquisition of oncocytic morphology. IOPN is a distinct pancreatic neoplasm with specific clinicopathologic and molecular features. Considering the clinical or prognostic implications, its recognition is essential for pathologists and, ultimately, patients' management.

Intra-ampullary Papillary Tubular Neoplasm (IAPN): Clinicopathologic Analysis of 72 Cases Highlights the Distinctive Characteristics of a Poorly Recognized Entity

The guidelines recently recognized the intra-ampullary papillary tubular neoplasm (IAPN) as a distinct tumor entity. However, the data on IAPN and its distinction from other ampullary tumors remain limited. A detailed clinicopathologic analysis of 72 previously unpublished IAPNs was performed. The patients were: male/female=1.8; mean age=67 years (range: 42 to 86 y); mean size=2.3 cm. Gross-microscopic correlation was crucial. From the duodenal perspective, the ampulla was typically raised symmetrically, with a patulous orifice, and was otherwise covered by stretched normal duodenal mucosa. However, in 6 cases, the protrusion of the intra-ampullary tumor to the duodenal surface gave the impression of an "ampullary-duodenal tumor," with the accurate diagnosis of IAPN established only by microscopic correlation illustrating the abrupt ending of the lesion at the edge of the ampulla. Microscopically, the preinvasive component often revealed mixed phenotypes (44.4% predominantly nonintestinal). The invasion was common (94%), typically small (mean=1.2 cm), primarily pancreatobiliary-type (75%), and showed aggressive features (lymphovascular invasion in 66%, perineural invasion in 41%, high budding in 30%). In 6 cases, the preinvasive component was pure intestinal, but the invasive component was pancreatobiliary. LN metastasis was identified in 42% (32% in those with ≤1 cm invasion). The prognosis was significantly better than ampullary-ductal carcinomas (median: 69 vs. 41 months; 3-year: 68% vs. 55%; and 5-year: 51% vs. 35%, P =0.047). In conclusion, unlike ampullary-duodenal carcinomas, IAPNs are often (44.4%) predominantly nonintestinal and commonly (94%) invasive, displaying aggressive features and LN metastasis even when minimally invasive, all of which render them less amenable to ampullectomy. However, their prognosis is still better than that of the "ampullary-ductal" carcinomas, with which IAPNs are currently grouped in CAP protocols (while IAPNs are kindreds of intraductal tumors of the pancreatobiliary tract, the latter represents the ampullary counterpart of pancreatic adenocarcinoma/cholangiocarcinoma).

Diagnosis and Management of Pancreatic Cysts

As pancreatic cyst incidence rises, likely due to the ubiquitous increase in cross-sectional imaging, their management presents multiple challenges for both the practitioner and patient. It is critical that all pancreatic cysts are appropriately characterized, as treatment decisions depend on an accurate diagnosis. Diagnostic modalities such as cytology, biopsy, and cyst fluid biomarkers allow for definitive diagnosis of virtually all lesions. Some cysts, such as intraductal papillary mucinous neoplasms, mucinous cystic neoplasms, and cystic pancreatic endocrine neoplasms, have malignant potential and must be surveyed. Other cysts, such as serous cystadenomas and pancreatic fluid collections, do not have malignant potential. Surveillance strategies vary widely depending on cyst type and size and while multiple medical societies advocate surveillance, their published surveillance guidelines are heterogenous. Cysts with high-risk stigmata or worrisome features are usually resected, depending on the patient's surgical fitness. In patients unfit for resection, newer endoscopic ablative techniques are advocated. Controversial aspects regarding cyst management include whether surveillance can be stopped, how surveillance should be performed, and the extensive financial burden cyst management places on the health care system. Further study into the natural history of cystic lesions, including definitive determination of the rate of malignant transformation for each cyst type, is essential.

Multi-omic profiling of intraductal papillary neoplasms of the pancreas reveals distinct expression patterns and potential markers of progression

In order to advance our understanding of precancers in the pancreas, 69 pancreatic intraductal papillary neoplasms (IPNs), including 64 intraductal papillary mucinous neoplasms (IPMNs) and 5 intraductal oncocytic papillary neoplasms (IOPNs), 32 pancreatic cyst fluid samples, 104 invasive pancreatic ductal adenocarcinomas (PDACs), 43 normal adjacent tissues (NATs), and 76 macro-dissected normal pancreatic ducts (NDs) were analyzed by mass spectrometry. A total of 10,246 proteins and 22,284 glycopeptides were identified in all tissue samples, and 756 proteins with more than 1.5-fold increase in abundance in IPMNs relative to NDs were identified, 45% of which were also identified in cyst fluids. The over-expression of selected proteins was validated by immunolabeling. Proteins and glycoproteins overexpressed in IPMNs included those involved in glycan biosynthesis and the immune system. In addition, multiomics clustering identified two subtypes of IPMNs. This study provides a foundation for understanding tumor progression and targets for earlier detection and therapies.

Significance

This multilevel characterization of intraductal papillary neoplasms of the pancreas provides a foundation for understanding the changes in protein and glycoprotein expression during the progression from normal duct to intraductal papillary neoplasm, and to invasive pancreatic carcinoma, providing a foundation for informed approaches to earlier detection and treatment.

PanIN or IPMN? Redefining Lesion Size in 3 Dimensions

Pancreatic ductal adenocarcinoma (PDAC) develops from 2 known precursor lesions: a majority (∼85%) develops from pancreatic intraepithelial neoplasia (PanIN), and a minority develops from intraductal papillary mucinous neoplasms (IPMNs). Clinical classification of PanIN and IPMN relies on a combination of low-resolution, 3-dimensional (D) imaging (computed tomography, CT), and high-resolution, 2D imaging (histology). The definitions of PanIN and IPMN currently rely heavily on size. IPMNs are defined as macroscopic: generally >1.0 cm and visible in CT, and PanINs are defined as microscopic: generally <0.5 cm and not identifiable in CT. As 2D evaluation fails to take into account 3D structures, we hypothesized that this classification would fail in evaluation of high-resolution, 3D images. To characterize the size and prevalence of PanINs in 3D, 47 thick slabs of pancreas were harvested from grossly normal areas of pancreatic resections, excluding samples from individuals with a diagnosis of an IPMN. All patients but one underwent preoperative CT scans. Through construction of cellular resolution 3D maps, we identified >1400 ductal precursor lesions that met the 2D histologic size criteria of PanINs. We show that, when 3D space is considered, 25 of these lesions can be digitally sectioned to meet the 2D histologic size criterion of IPMN. Re-evaluation of the preoperative CT images of individuals found to possess these large precursor lesions showed that nearly half are visible on imaging. These findings demonstrate that the clinical classification of PanIN and IPMN fails in evaluation of high-resolution, 3D images, emphasizing the need for re-evaluation of classification guidelines that place significant weight on 2D assessment of 3D structures.

Utility of Radiological Follow Up of Main-Duct Intraductal Papillary Mucinous Neoplasms and Mixed-Type Intraductal Papillary Mucinous Neoplasms

BACKGROUND

Intraductal papillary mucinous neoplasms (IPMNs) have the potential to evolve into pancreatic adenocarcinoma (PDAC). While main-duct IPMNs (MD-IPMNs), involving the main pancreatic duct (MPD), are less common than side-branch IPMNs (SB-IPMNs) or mixed-type IPMNs (mixed-IPMNs), their malignant transformation potential is far greater. Controversy exists between different guidelines in terms of recommended management strategies. This study was aimed at assessing the utility of the radiological follow up of MD-IPMNs and mixed-type IPMNs, including prevalence of worrisome radiological findings as well as clinical and laboratory parameters, and their correlation with the development of progression or pancreatic adenocarcinoma.

METHODS

Eighty-four patients with MD-IPMNs or mixed-type IPMNs who underwent at least one magnetic resonance cholangiopancreatography (MRCP) were included. Clinical and laboratory data were obtained retrospectively. A cross-sectional analysis was carried out to establish clinical and laboratory parameters associated with development of PDAC. A retrospective cohort analysis was performed on 44 patients who had at least six months of follow up, trying to identify factors correlating with worrisome radiological features.

RESULTS

Nine cases (10.7%) of PDAC were recorded in this cohort. The laboratory and imaging factors associated with cyst size progression greater than 5 mm during follow up were elevated alanine transaminase (ALT) levels, the maximal cyst size, and the MPD diameter. Cross-sectional analysis indicated that PDAC was associated with nausea (p = 0.01), as well as increased levels of aspartate aminotransferase (AST) (p = 0.05), gamma glutamyl transpeptidase (GGT) (p = 0.01), and alkaline phosphatase (ALP) (p = 0.01).

CONCLUSIONS

Elevated levels of liver enzymes were associated with IPMN progression and, subsequently, the development of PDAC. ALT levels, maximal cyst size, and MPD diameter are associated with the progression of cyst size. These data may aid in risk-stratifying patients when determining the follow up approach for IPMNs.

Comparative Assessment of Endoscopic Ultrasound-Guided Biopsies vs. Percutaneous Biopsies of Pancreatic Lesions: A Systematic Review and Meta-Analysis of Diagnostic Performance

Introduction: Pancreatic cancer ranks as the fourth deadliest form of cancer. However, it is essential to note that not all pancreatic masses signal primary malignancy. Therefore, it is imperative to establish the correct differential diagnosis, a process further supported by pre-operative biopsy procedures. This meta-analysis aims to compare the diagnostic performance of two minimally invasive biopsy approaches for pancreatic tissue sampling: percutaneous biopsies guided by computed tomography or ultrasound, and transduodenal biopsies guided by endoscopic ultrasound (EUS). Methods: A systematic literature search was conducted in the MEDLINE and Scopus databases. The included studies analyzed the diagnostic performance of the two biopsy methods, and they were assessed for risk of bias using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Statistical analysis was carried out using the RevMan and MetaDisc software packages. Results: The statistical analysis of the results demonstrated the superiority of the percutaneous approach. Specifically, the pooled sensitivity, specificity, LR+, LR-and DOR for the percutaneous approach were 0.896 [95% CI: 0.878-0.913], 0.949 [95% CI: 0.892-0.981], 9.70 [95% CI: 5.20-18.09], 0.20 [95% CI: 0.12-0.32] and 68.55 [95% CI: 32.63-143.98], respectively. The corresponding values for EUS-guided biopsies were 0.806 [95% CI: 0.775-0.834], 0.955 [95% CI: 0.926-0.974], 12.04 [95% CI: 2.67-54.17], 0.24 [95% CI: 0.15-0.39] and 52.56 [95% CI: 13.81-200.09], respectively. Nevertheless, it appears that this statistical superiority is also linked to the selection bias favoring larger and hence more readily accessible tumors during percutaneous biopsy procedures. Conclusions: Concisely, our meta-analysis indicates the statistical superiority of the percutaneous approach. However, selecting the optimal biopsy method is complex, influenced by factors like patient and tumor characteristics, clinical resources, and other relevant considerations.

Molecular Pathology of Pancreatic Cystic Lesions with a Focus on Malignant Progression

The malignant progression of pancreatic cystic lesions (PCLs) remains understudied with a knowledge gap, yet its exploration is pivotal for effectively stratifying patient risk and detecting cancer at its earliest stages. Within this review, we delve into the latest discoveries on the molecular level, revealing insights into the IPMN molecular landscape and revised progression model, associated histologic subtypes, and the role of inflammation in the pathogenesis and malignant progression of IPMN. Low-grade PCLs, particularly IPMNs, can develop into high-grade lesions or invasive carcinoma, underscoring the need for long-term surveillance of these lesions if they are not resected. Although KRAS and GNAS remain the primary oncogenic drivers of neoplastic development in IPMNs, additional genes that are important in tumorigenesis have been recently identified by whole exome sequencing. A more complete understanding of the genes involved in the molecular progression of IPMN is critical for effective monitoring to minimize the risk of malignant progression. Complicating these strategies, IPMNs are also frequently multifocal and multiclonal, as demonstrated by comparative molecular analysis. Algorithms for preoperative cyst sampling and improved radiomic techniques are emerging to model this spatial and temporal genetic heterogeneity better. Here, we review the molecular pathology of PCLs, focusing on changes associated with malignant progression. Developing models of molecular risk stratification in PCLs which can complement radiologic and clinical features, facilitate the early detection of pancreatic cancer, and enable the development of more personalized surveillance and management strategies are summarized.

Cell of Origin of Pancreatic cancer: Novel Findings and Current Understanding

ABSTRACT

Pancreatic ductal adenocarcinoma (PDAC) stands as one of the most lethal diseases globally, boasting a grim 5-year survival prognosis. The origin cell and the molecular signaling pathways that drive PDAC progression are not entirely understood. This review comprehensively outlines the categorization of PDAC and its precursor lesions, expounds on the creation and utility of genetically engineered mouse models used in PDAC research, compiles a roster of commonly used markers for pancreatic progenitors, duct cells, and acinar cells, and briefly addresses the mechanisms involved in the progression of PDAC. We acknowledge the value of precise markers and suitable tracing tools to discern the cell of origin, as it can facilitate the creation of more effective models for PDAC exploration. These conclusions shed light on our existing understanding of foundational genetically engineered mouse models and focus on the origin and development of PDAC.

International evidence-based Kyoto guidelines for the management of intraductal papillary mucinous neoplasm of the pancreas

This study group aimed to revise the 2017 international consensus guidelines for the management of intraductal papillary mucinous neoplasm (IPMN) of the pancreas, and mainly focused on five topics; the revision of high-risk stigmata (HRS) and worrisome features (WF), surveillance of non-resected IPMN, surveillance after resection of IPMN, revision of pathological aspects, and investigation of molecular markers in cyst fluid. A new development from the prior guidelines is that systematic reviews were performed for each one of these topics, and published separately to provide evidence-based recommendations. One of the highlights of these new "evidence-based guidelines" is to propose a new management algorithm, and one major revision is to include into the assessment of HRS and WF the imaging findings from endoscopic ultrasound (EUS) and the results of cytological analysis from EUS-guided fine needle aspiration technique, when this is performed. Another key element of the current guidelines is to clarify whether lifetime surveillance for small IPMNs is required, and recommends two options, "stop surveillance" or "continue surveillance for possible development of concomitant pancreatic ductal adenocarcinoma", for small unchanged BD-IPMN after 5 years surveillance. Several other points are also discussed, including identifying high-risk features for recurrence in patients who underwent resection of non-invasive IPMN with negative surgical margin, summaries of the recent observations in the pathology of IPMN. In addition, the emerging role of cyst fluid markers that can aid in distinguishing IPMN from other pancreatic cysts and identify those IPMNs that harbor high-grade dysplasia or invasive carcinoma is discussed.

Early Cancerous Lesions of the Pancreas and Ampulla: Current Concepts and Challenges

Owing to the increased use of advanced imaging techniques, mass-forming (cystic/intraductal) preinvasive neoplasms are being detected much more frequently and they have rapidly become one of the main focuses of interests in medical field. These neoplasms have very distinctive clinical and radiographic findings, exhibit a spectrum of dysplastic transformation, from low-grade dysplasia to high-grade dysplasia, and may be associated with an invasive carcinoma. Accounting for about 5% to 10% of pancreatic ductal adenocarcinomas, they provide a curable target subset in an otherwise biologically dismal pancreas cancer category.

A case report of carcinoma of the papilla of Vater associated with a hyperplasia-dysplasia-carcinoma sequence by pancreaticobiliary maljunction

BACKGROUND

Pancreaticobiliary maljunction (PBM) is a known risk factor for biliary tract cancer. However, its association with carcinoma of the papilla of Vater (PVca) remains unknown. We report a case with PVca that was thought to be caused by the hyperplasia-dysplasia-carcinoma sequence, which is considered a mechanism underlying PBM-induced biliary tract cancer.

CASE PRESENTATION

A 70-year-old woman presented with white stool and had a history of cholecystectomy for the diagnosis of a non-dilated biliary tract with PBM. Esophagogastroduodenoscopy revealed a tumor in the papilla of Vater, and PVca was histologically proven by biopsy. We finally diagnosed her with PVca concurrent with non-biliary dilated PBM (cT1aN0M0, cStage IA, according to the Union for International Cancer Control, 8th edition), and subsequently performed subtotal stomach-preserving pancreaticoduodenectomy. Pathological findings of the resected specimen revealed no adenomas and dysplastic and hyperplastic mucosae in the common channel slightly upstream of the main tumor, suggesting a PBM related carcinogenic pathway with hyperplasia-dysplasia-carcinoma sequence. Immunostaining revealed positivity for CEA. CK7 positivity, CK20 negativity, and MUC2 negativity indicated that this PVca was of the pancreatobiliary type. Genetic mutations were exclusively detected in tumors and not in normal tissues, and bile ducts from formalin-fixed paraffin-embedded samples included mutated-ERBB2 (Mutant allele frequency, 81.95%). Moreover, of the cell-free deoxyribonucleic acid (cfDNA) extracted from liquid biopsy mutated-ERBB2 was considered the circulating-tumor deoxyribonucleic acid (ctDNA) of this tumor.

CONCLUSIONS

Herein, we report the first case of PVca with PBM potentially caused by a "hyperplasia-dysplasia-carcinoma sequence" detected using immunostaining and next-generation sequencing. Careful follow-up is required if pancreaticobiliary reflux persists, considering the possible development of PVca.

A case of pseudomyxoma peritonei arising from a perforated intraductal papillary mucinous neoplasm that underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

Pseudomyxoma peritonei (PMP) of pancreatic origin arising from an intraductal papillary mucinous neoplasm (IPMN) is rare. Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) has been established as the optimal treatment for PMP. However, the benefits and safety of CRS with HIPEC for treating PMP of pancreatic origin remain unclear. Herein, we describe a case of PMP of pancreatic origin that was treated with CRS and HIPEC without postoperative complications. A 75-year-old woman was referred to our department. Computed tomography (CT) revealed a multilocular cystic tumor in the pancreatic tail, notable mucinous ascites in the abdominal cavity, and scalloping of the liver and spleen. CT did not reveal the appendix, and the ovaries were normal in size. The patient was diagnosed with PMP of pancreatic origin, and CRS and HIPEC were performed. Intraoperatively, the pancreatic tumor was perforated, and there was a large amount of mucinous ascites. We performed distal pancreatectomy in addition to CRS and HIPEC, with no intraoperative complications. The postoperative course was uneventful, and the patient survived after 6 months without recurrence. CRS with HIPEC may be a feasible treatment option for PMP of pancreatic origin.

Gene Rearrangement and Expression of PRKACA and PRKACB Govern Morphobiology of Pancreatobiliary Oncocytic Neoplasms

Intraductal oncocytic papillary neoplasms (IOPNs) are distinct from intraductal papillary mucinous neoplasms based on characteristic morphologic and genetic features represented by fusion genes involving PRKACA or PRKACB (PRKACA/B). However, pancreatic and biliary tumors with partial oncocytic features are often encountered clinically, and their molecular features are yet to be clarified. This study included 80 intraductal papillary neoplasms: 32 tumors with mature IOPN morphology (typical), 28 with partial or subclonal oncocytic features (atypical), and 20 without oncocytic features (control). We analyzed PRKACA/B fusion genes, including ATP1B1::PRKACA, DNAJB1::PRKACA, and ATP1B1::PRKACB, by reverse-transcription PCR; mRNA expression of fusion genes and nonrearranged PRKACA/B genes by quantitative reverse-transcription PCR; mutations in KRAS, BRAF, and GNAS by targeted sequencing or droplet digital PCR; and the expression of cyclic adenosine monophosphate (cAMP)-dependent protein kinase catalytic subunits α (PRKACA) and β (PRKACB), phosphorylated cAMP response element-binding protein, and aberrations of p16, p53, SMAD4, STK11, and β-catenin by immunohistochemistry. PRKACA/B fusion genes were detected in 100% (32/32) of typical, 46% (13/28) of atypical, and 0% (0/20) of control (P < .05). Expression of PRKACA, PRKACB, and phosphorylated cAMP response element-binding protein was upregulated in neoplasms with PRKACA/B fusion genes (P < .05). mRNA expression of the PRKACA/B fusion genes and protein expression of PRKACA or PRKACB tended to be higher in typical than in atypical cases (mRNA, P = .002; protein expression, P = .054). In some atypical neoplasms with mixed subtypes, PRKACA/B fusion genes were superimposed exclusively on oncocytic components. Typical IOPNs harbored fewer KRAS and GNAS mutations than control samples and fewer alterations in p53 and STK11 than atypical samples (P < .05). In conclusion, PRKACA/B fusion genes not only are the characteristic drivers of IOPNs but also play a crucial role in the development of subclonal oncocytic neoplasms. Moreover, oncocytic morphology is strongly associated with upregulation of PRKACA/B, which may provide clues for potential therapeutic options.

Acute pancreatitis in intraductal papillary mucinous neoplasm: a single-center retrospective cohort study with systematic review and meta-analysis

BACKGROUND

Intraductal papillary mucinous neoplasm (IPMN) is a cystic tumor of the pancreas arising from abnormal papillary proliferation of ductal epithelial cells, and is a precancerous lesion of pancreatic malignancy. This study aimed to evaluate associations between acute pancreatitis (AP) and histologic subtypes of IPMN.

METHODS

In the clinical study, patients with IPMN confirmed by surgical resection specimens at our institute between 2009 and 2021 were eligible for inclusion. Associations and predictive accuracy of AP on the presence of HGD were determined by logistic regressions. In addition, a systematic review and meta-analysis was conducted through literatures upon search in PubMed, Embase, CENTRAL, China National Knowledge Infrastructure (CKNI), and Wanfang database, up to June, 2023. Pooled effects of the associations between AP and HGD and intestinal epithelial subtype subtype, shown as odds ratios (ORs) with 95% confidence intervals (CIs), were calculated using random effects model.

RESULTS

The retrospective cohort study included 47 patients (32 males, 15 females) diagnosed with IPMN at our center between 2009 and 2021, including 11 cases with AP (median 62 years) and 36 cases (median 64.5 years) without. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of AP in predicting HGD were 78.7%, 57.1%, 82.5%, 36.4%, and 91.7%, respectively. Univariate logistic regression analysis showed that AP group had greater odds of presence of HGD (OR: 6.29,95% CI: 1.14-34.57) than non-AP group. Meta-analysis of five case-control studies in the literature included 930 patients and showed that AP-IPMN patients had higher odds for HGD (OR: 2.13, 95% CI 1.38-3.29) and intestinal epithelial subtype (OR: 5.38, 95% CI: 3.50-8.27) compared to non-AP IPMN.

CONCLUSIONS

AP is predictive of malignancy in patients with IPMN.

Co-occurring IPMN and pancreatic cancer: the same or different? An overview from histology to molecular pathology

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas is one of the most well-established precursors of pancreatic cancer. Its progression to acquire invasiveness is a complex process, based on the accumulation of morphological and genetic alterations. Recent advances in DNA sequencing also showed that co-occurring IPMNs and pancreatic cancers could be totally independent, further complicating our understanding of this complex scenario. The distinction between IPMN and related pancreatic cancer vs IPMN and co-occurring-but not related-pancreatic cancer is a challenging task in routine diagnostic activity, but may have important implications for precision oncology. Of note, recent multiregional sequencing-based studies focused not only on IPMN multi-step tumourigenesis, but also on the divergent intratumoural heterogeneity of this neoplasm. Globally considered, there are three different situations in which co-occurring IPMNs and invasive carcinomas can be found in the same pancreata, indicated with different terminologies: (1) IPMN-associated carcinoma: this definition indicates a carcinoma arising from an IPMN and can be also defined as IPMN-derived carcinoma, sequential or likely related; (2) independent IPMN and invasive carcinoma: the two lesions are not related, and this situation is defined as concomitant, de novo or likely independent; (3) branch-off pathway, where an invasive carcinoma and an adjacent IPMN develop divergently in a forked fashion from a common ancestral clone. In this review, we aim at clarifying the most important nomenclature/definitions of these different situations, also providing an overview of the molecular state-of-the-art and of the clinical implications of this complex landscape.

Intraductal neoplasms of the pancreatobiliary tract: navigating the alphabet

Cancers of the pancreatobiliary tract are diseases with unfavourable prognoses. In the last couple of decades, two types of lesions have been described as precursors that precede pancreatobiliary cancers. These include incidental microscopic (flat) lesions known as pancreatic intra-epithelial neoplasia and biliary intra-epithelial neoplasia, and grossly visible, mass-forming lesions (tumoral intra-epithelial neoplasia) including intraductal papillary mucinous neoplasms, intraductal oncocytic papillary neoplasms, intraductal tubulopapillary neoplasms, intraductal papillary neoplasms of the bile duct and intracholecystic papillary neoplasms. Early detection and adequate treatment of these precursor lesions, especially the second group, have the potential to prevent pancreatobiliary cancer or at least improve its prognosis. In this review, we discuss their histopathology and recent updates on molecular profiling of these intraductal neoplasms of the pancreatobiliary tract.

Preoperatively diagnosed intraductal oncocytic papillary neoplasm of the pancreas with prominent invasion: a case report

Previously considered as one of the less-invasive subtypes of intraductal papillary mucinous neoplasm, intraductal oncocytic papillary neoplasm (IOPN) has recently been acknowledged as a new entity of pancreatic tumor. We herein present a case of preoperatively diagnosable IOPN invasion in the stomach and colon. A 78-year-old woman was referred to our hospital for evaluation of anorexia and gastroesophageal reflux. Upper gastrointestinal endoscopy revealed a gastric subepithelial lesion with ulcerated mucosa that required hemostasis. Computed tomography revealed a 96-mm-diameter solid tumor with a well-defined border and centrally positioned necrotic area, extending from the stomach to the transverse colon and pancreatic tail. Because it was suspected to be a pancreatic solid tumor with direct stomach invasion, endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) was performed, which led to a preoperative diagnosis of IOPN. Moreover, laparoscopic pancreatosplenectomy, proximal gastrectomy, and transverse colectomy were performed. Analysis of the surgical specimen revealed that the tumor was IOPN and had invaded the stomach and transverse colon. Lymph node metastasis was also confirmed. These findings indicate that IOPN can manifest as an invasive tumor, and EUS-FNB may be equally helpful for assessing the invaded area of a cystic lesion as it is for a solid lesion.

Circulating Epithelial Cells in Patients with Intraductal Papillary Mucinous Neoplasm of the Pancreas

Intraductal papillary mucinous neoplasm (IPMN) is the most common pancreatic cyst and a precursor of pancreatic cancer (PDAC). Since PDAC has a devastatingly high mortality rate, the early diagnosis and treatment of any precursor lesion are rational. The safety of the existing guidelines on the clinical management of IPMN has been criticized due to unsatisfactory sensitivity and specificity, showing the need for further markers. Blood obtained from patients with IPMN was therefore subjected to size-based isolation of circulating epithelial cells (CECs). We isolated CECs and evaluated their cytological characteristics. Additionally, we compared Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations in CECs and the primary IPMN tissue, since KRAS mutations are very typical for PDAC. Samples from 27 IPMN patients were analyzed. In 10 (37%) patients, CECs were isolated and showed a hybrid pattern of surface markers involving both epithelial and mesenchymal markers, suggesting a possible EMT process of the cells. Especially, patients with high-grade dysplasia in the main specimen were all CEC-positive. KRAS mutations were also present in CECs but less common than in IPMN tissue. The existence of CEC in IPMN patients offers additional blood-based research possibilities for IMPN biology.

A Unicorn Disease: The Large Duct Variant of Invasive Ductal Adenocarcinoma of the Pancreas

Large duct adenocarcinoma (LDA) is a rare histopathological variant of pancreatic ductal adenocarcinoma (PDAC) that closely mimics intraductal papillary mucinous neoplasm (IPMN). We present a 74-year-old female diagnosed with LDA in 2017. She was initially managed with chemotherapy and laparoscopic distal pancreatectomy. After five years of stable disease on systemic chemotherapy, she was referred to us to explore further definitive treatments. We used a multidisciplinary approach with curative-intent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC), followed by oral maintenance chemotherapy. Subsequent scans showed stable disease; she eventually underwent neoadjuvant radiation and surgery with intraoperative radiation therapy (IORT) and achieved remission.

Comprehensive DNA Methylation Analysis Indicates That Pancreatic Intraepithelial Neoplasia Lesions Are Acinar-Derived and Epigenetically Primed for Carcinogenesis

Pancreatic ductal adenocarcinoma (PDAC) is believed to arise from the accumulation of a series of somatic mutations and is also frequently associated with pancreatic intraepithelial neoplasia (PanIN) lesions. However, there is still debate as to whether the cell type-of-origin of PanINs and PDACs in humans is acinar or ductal. As cell type identity is maintained epigenetically, DNA methylation changes during pancreatic neoplasia can provide a compelling perspective to examine this question. Here, we performed laser-capture microdissection on surgically resected specimens from 18 patients to isolate, with high purity, DNA for whole-genome bisulfite sequencing from four relevant cell types: acini, nonneoplastic ducts, PanIN lesions, and PDAC lesions. Differentially methylated regions (DMR) were identified using two complementary analytical approaches: bsseq, which identifies any DMRs but is particularly useful for large block-like DMRs, and informME, which profiles the potential energy landscape across the genome and is particularly useful for identifying differential methylation entropy. Both global methylation profiles and block DMRs clearly implicated an acinar origin for PanINs. At the gene level, PanIN lesions exhibited an intermediate acinar-ductal phenotype resembling acinar-to-ductal metaplasia. In 97.6% of PanIN-specific DMRs, PanIN lesions had an intermediate methylation level between normal and PDAC, which suggests from an information theory perspective that PanIN lesions are epigenetically primed to progress to PDAC. Thus, epigenomic analysis complements histopathology to define molecular progression toward PDAC. The shared epigenetic lineage between PanIN and PDAC lesions could provide an opportunity for prevention by targeting aberrantly methylated progression-related genes.

SIGNIFICANCE

Analysis of DNA methylation landscapes provides insights into the cell-of-origin of PanIN lesions, clarifies the role of PanIN lesions as metaplastic precursors to human PDAC, and suggests potential targets for chemoprevention.

HNF1B-driven three-dimensional chromatin structure for molecular classification in pancreatic cancers

The molecular subtypes of pancreatic cancer (PC), either classical/progenitor-like or basal/squamous-like, are currently a major topic of research because of their direct association with clinical outcomes. Some transcription factors (TFs) have been reported to be associated with these subtypes. However, the mechanisms by which these molecular signatures of PCs are established remain unknown. Epigenetic regulatory processes, supported by dynamic changes in the chromatin structure, are essential for transcriptional profiles. Previously, we reported the importance of open chromatin profiles in the biological features and transcriptional status of PCs. Here, we aimed to analyze the relationships between three-dimensional (3D) genome structures and the molecular subtypes of human PCs using Hi-C analysis. We observed a correlation of the specific elements of 3D genome modules, including compartments, topologically associating domains, and enhancer-promoter loops, with the expression of related genes. We focused on HNF1B, a TF that is implicated in the progenitor subtype. Forced expression of HNF1B in squamous-type PC organoids induced the upregulation and downregulation of genes associated with progenitor and squamous subtypes, respectively. Long-range genomic interactions induced by HNF1B were accompanied by compartment modulation and H3K27ac redistribution. We also found that these HNF1B-induced changes in subtype-related gene expression required an intrinsically disordered region, suggesting a possible involvement of phase separation in compartment modulation. Thus, mapping of 3D structural changes induced by TFs, such as HNF1B, may become a useful resource for further understanding the molecular features of PCs.

Adenosquamous carcinoma coexisting with intraductal papillary mucinous neoplasm of the pancreas: a case report

BACKGROUND

Adenosquamous carcinoma of the pancreas is a rare variant, with a worse prognosis than pancreatic ductal adenocarcinoma; moreover, it has characteristic clinical and histopathological features. Studies have mentioned the differentiation of intraductal papillary mucinous neoplasms into mucinous/tubular adenocarcinomas; however, their transdifferentiation into adenosquamous carcinoma remains unclear.

CASE PRESENTATION

An 80-year-old Japanese woman was referred to our hospital for further examination of multiple pancreatic cysts. Enhanced computed tomography after close follow-up for 6 years revealed a new nodule with poor enhancement on the pancreatic body. Distal pancreatectomy and splenectomy were performed. Histopathological examination revealed an adenosquamous carcinoma with coexisting intraductal papillary mucinous neoplasms; moreover, the intraductal papillary mucinous neoplasms lacked continuity with the adenosquamous carcinoma. Immunohistochemical analysis revealed squamous cell carcinoma and differentiation from adenocarcinoma to squamous cell carcinoma. Gene mutation analysis revealed KRASG12D and KRASG12R mutations in adenosquamous carcinoma components and intraductal papillary mucinous neoplasm lesions, respectively, with none showing the mutation of GNAS codon 201. The final histopathological diagnosis was adenosquamous carcinoma with coexisting intraductal papillary mucinous neoplasms of the pancreas.

CONCLUSIONS

This is the rare case of adenosquamous carcinoma with coexisting intraductal papillary mucinous neoplasms of the pancreas. To investigate the underlying transdifferentiation pathway of intraductal papillary mucinous neoplasms into this rare subtype of pancreatic cancer, we explored gene mutation differences as a clinicopathological parameter.

Simultaneous and sequential combination of genetic and epigenetic biomarkers for the presence of high-grade dysplasia in patients with pancreatic cyst: Discovery in cyst fluid and test in pancreatic juice

BACKGROUND/OBJECTIVES

Screening patients with intraductal papillary mucinous neoplasms (IPMN) has the primary goal of identifying potentially curable noninvasive precursors. We aimed to evaluate the diagnostic impact of genetic and epigenetic biomarkers in the presence of noninvasive precursors.

METHODS

Mutated KRAS/GNAS and methylated SOX17/TBX15/BMP3/TFPI2 DNA were assessed by droplet digital PCR in a discovery cohort of 70 surgically aspirated cyst fluids, and diagnostic performances for differentiating high-grade dysplasia (HGD) from low-grade dysplasia (LGD) was evaluated. We then tested these markers using an independent test cohort consisting of 156 serially collected pancreatic juice samples from 30 patients with IPMN.

RESULTS

Mutated KRAS and GNAS are specific for IPMNs but are not helpful for the prediction of histological grades. Cyst fluids from IPMN with HGD showed higher methylation levels of SOX17 (median, 0.141 vs. 0.021; P = 0.086) and TBX15 (median, 0.030 vs. 0.003; P = 0.028) than those with LGD. The combination of all tested markers yielded a diagnostic performance with sensitivity of 69.6%, and specificity of 90.0%. Among the 30 pancreatic juice samples exhibiting the highest abundance of KRAS/GNAS mutations in each patient in the test cohort, patients with histologically proven HGD due to pancreatic resection had a significantly higher prevalence (100% vs. 31%, P = 0.018) and abundance (P = 0.037) of methylated TBX15 than those without cytohistological diagnosis undergoing surveillance.

CONCLUSIONS

A simultaneous and sequential combination of mutated and methylated DNA markers in pancreatic cyst fluid and juice sample markers can help detect noninvasive pancreatic precursor neoplasms.

Serine/Threonine Kinase 11 Plays a Canonical Role in Malignant Progression of KRAS -Mutant and GNAS -Wild-Type Intraductal Papillary Mucinous Neoplasms of the Pancreas

OBJECTIVE

We aimed to elucidate the clinicopathobiological significance of Serine/Threonine Kinase 11 (STK11) in pancreatic intraductal papillary mucinous neoplasms (IPMNs).

BACKGROUND

STK11 is a tumor suppressor involved in certain IPMNs; however, its significance is not well known.

METHODS

In 184 IPMNs without Peutz-Jeghers syndrome, we analyzed expression of STK11 and phosphorylated-AMPKa in all cases, and p16, p53, SMAD4, and β-catenin in 140 cases by immunohistochemistry; and we analyzed mutations in 37 genes, including whole coding exons of STK11, CDKN2A, TP53, and SMAD4, and hotspots of KRAS, BRAF, and GNAS in 64 cases by targeted sequencing. KRAS and GNAS were additionally analyzed in 86 STK11-normal IPMNs using digital-PCR.

RESULTS

Consistent loss or reduction of STK11 expression was observed in 26 of 184 (14%) IPMNs. These STK11-aberrant IPMNs were 17 of 45 (38%) pancreatobiliary, 8 of 27 (30%) oncocytic, 1 of 54 (2%) gastric, and 0 of 58 (0%) intestinal subtypes ( P = 8.5E-11), and 20 of 66 (30%) invasive, 6 of 74 (8%) high-grade, and 0 of 44 (0%) low-grade ( P = 3.9E-06). Sixteen somatic STK11 mutations (5 frameshift, 6 nonsense, 1 splicing, and 4 missense) were detected in 15/26 STK11-aberrant IPMNs ( P = 4.1E-06). All STK11-aberrantIPMNs were GNAS -wild-type and 96% of them were KRAS or BRAF -mutant.Morphologically, STK11-aberrant IPMNs presented "fern-like" arborizing papillae with thin fibrovascular core. Phosphorylated-AMPKa was down-regulated in STK11-aberrant IPMNs (92%, P = 6.8E-11). Patients with STK11-aberrant IPMNs showed poorer survival than patients with STK11-normal IPMNs ( P = 3.6E-04 overall; P = 6.1E-04 disease-free).

CONCLUSION

STK11 may play a canonical role in malignant progression and poor survival of patients with IPMNs. Aberrant STK11-driven phosphorylated AMPK downregulation may provide therapeutic opportunities with mTOR inhibitors/AMPK activators.

Intraductal tubulopapillary neoplasms of the bile ducts: identity, clinicopathologic characteristics, and differential diagnosis of a distinct entity among intraductal tumors

Among the mass-forming preinvasive (tumoral intraepithelial) neoplasms of the biliary tract, intraductal tubulopapillary neoplasms (ITPN-Bs) are increasingly being recognized as a separate category. By being intramucosal polypoid proliferations of dysplastic/neoplastic cells, they are highly similar to other members of the "intraductal neoplasms (IDNs)" category (namely, intraductal papillary neoplasms [IPNBs], and intraductal oncocytic papillary neoplasms [IOPNs]); however, they are distinguished by MUC6-expressing nonmucinous cells that lack intestinal differentiation and form striking tubular configuration. Their molecular/genetic profile is also proving to be different with frequent alterations in cell cycle and chromatin remodeling genes, which are quite uncommon in other IDNs and cholangiocarcinomas. Despite the conceptual overlaps, they are also very different from intracholecystic nonmucinous tubular neoplasms (ICTN) of the gallbladder with the latter being associated with Wnt/beta-catenin pathway alterations, and almost never invasive. In contrast, ITPN-Bs are invasive in an estimated 80% of the cases, although even invasive examples often exhibit a protracted course. Invasive carcinomas arising from ITPN-Bs are overall similar to cholangiocarcinomas (including small duct and large duct patterns) but also often have peculiar characteristics such as more nodular-compact (blunt invasion) pattern. Like other IDNs, the ITPN-Bs have also been classified in the past as intraductal-spreading type of cholangiocarcinomas (and they are still regarded as such in some publications). In small biopsies, they are prone to be mistaken as ordinary adenocarcinomas because of their tubular pattern and pancreatobiliary cytology although their relatively monotonous cytology and zones of back-to-back tubule formation can help in their correct identification. Clinical presentation of ITPN-Bs is generally similar to other intraductal neoplasms; however, in the intrahepatic component, they tend to be more nodular than cystic, and their snake-like intraductal growth pattern is often more striking. In the management (diagnosis and treatment) of these tumors that are in essence adenoma-carcinoma sequence, the invasive and noninvasive components ought to be evaluated separately. Minimally invasive examples are commonly curable, and even those more extensively invasive may have a surprisingly good prognosis. In summary, biliary ITPNs form a distinct category not only clinicopathologically, immunophenotypically, and molecular-wise but regarding their biological behavior as well.

Endoscopic pancreatic sphincterotomy in patients with IPMN-related recurrent pancreatitis: A single center experience

BACKGROUND

Acute recurrent pancreatitis (ARP) is a rare manifestation of Intraductal Papillary Mucinous Neoplasms (IPMN) of the pancreas; ARP is a relative indication for pancreatic surgery in the setting of IPMN. Endoscopic pancreatic sphincterotomy (EPS) has been described as a minimal invasive treatment to reduce the episodes of ARP secondary to mucus migration in IPMN.

METHODS

patients with IPMN-related ARP treated with ESP from January 2004 to December 2020 were retrospectively selected. Clinical and technical data were recorded. A clinical follow-up (minimum 12 months) was performed to assess the number of episodes of AP occurring after EPS.

RESULTS

25 patients were included. The mean follow-up after ESP was 93.4 months (SD± 56.6). The mean number of AP before and after EPS were respectively 3.29 (SD ± 1.04) and 0.51 (SD ± 0.71). A complete response (no further episodes of AP) and a partial response (>50% reduction of AP episodes) were obtained in 64% and 24% of the cases, respectively, with an overall response rate of 88%. One post-EPS bleeding and one minor-papilla stenosis were reported and were endoscopically managed. Two patients underwent pancreatic resection for the occurrence of high-risk stigmata for cancer progression.

CONCLUSIONS

EPS is a safe and effective treatment to reduce the number of episodes of AP in selected patients with IPMNs-related ARP. Prospective trials are needed to confirm these data.

Pancreatic Cystic Lesions: A Focused Review on Cyst Clinicopathological Features and Advanced Diagnostics

Macroscopic, endomicroscopic, and histologic findings and correlation are an integral part of the diagnostic evaluation of pancreatic cystic lesions (PCLs), as complementing morphologic features seen by different specialties are combined to contribute to a final diagnosis. However, malignancy risk stratification of PCLs with worrisome features can still be challenging even after endoscopic ultrasound guided-fine needle aspiration (EUS-FNA) with cytological evaluation. This review aims to summarize cyst clinicopathological features from the pathologists' perspective, coupled with knowledge from advanced diagnostics-confocal laser endomicroscopy and cyst fluid molecular analysis, to demonstrate the state-of-art risk stratification of PCLs. This review includes illustrative photos of surgical specimens, endomicroscopic and histologic images, and a summary of cyst fluid molecular markers.

Negative correlation between the nuclear size and nuclear Lamina component Lamin A in intraductal papillary mucinous neoplasms of the pancreas

Background: The nuclear laminar protein Lamin A and inner nuclear membrane protein Emerin plays important role in sustaining nuclear structure. However, They have not investigated the significance of these proteins for development of pancreatic intraductal papillary mucinous neoplasm (IPMN). Methods: We examined pancreatic IPMN specimens for nuclear morphology and nuclear protein expression pattern of Lamin A and Emerin. Forty-two IPMN specimens were included, with 30 classified as intraductal papillary mucinous adenoma (IPMA) and 12 as intraductal papillary mucinous carcinoma (IPMC). Results: Classification according to histological subtype revealed that 26 specimens were of the gastric subtype (1 IPMC case), 8 were pancreatobiliary (6 IPMC cases), 6 were intestinal (3 IPMC cases), and 2 were oncocytic (all cases were IPMC). The frequency of IPMN subtypes in this study seemed to agree with those in previous reports. We analyzed Feulgen staining sections for nuclear morphological analysis using computer-assisted image analysis. Nuclear area and perimeter were significantly larger in IPMC than in IPMA. Finally, we examined the positive ratios of Lamin A and Emerin in immunohistochemical staining sections by image analysis. We found a negative correlation between the nuclear size and Lamin A-positive ratio, which was significantly lower in IPMC than that in IPMA. However, no significant correlation was observed between nuclear size and Emerin expression was observed, and no differences were found in the Emerin-positive ratio between IPMA and IPMC. Conclusion: Our results suggest that a decreased Lamin A positive ratio induces nuclear enlargement in adenomas, which thereby induce promotion to carcinomas. Furthermore, Lamin A expression can be a reliable biomarker for distinguishing between IPMC and IPMA.

Investigation of -PRKACA/-PRKACB fusion genes in oncocytic tumors of the pancreatobiliary and other systems

Intraductal oncocytic papillary neoplasms (IOPNs) of the pancreatobiliary system are tumors comprising oncocytic cells, in which three types of fusion genes involving -PRKACA/-PRKACB were recently identified. IOPNs infrequently combine with other histological subtypes of pancreatic intraductal papillary mucinous neoplasms (IPMNs) and intraductal papillary neoplasms of the bile duct (IPNBs). This study aimed to confirm the sensitivity/specificity of the fusion genes for IOPNs and to examine their significance in other oncocytic lesions. An RT-PCR, followed by DNA sequencing, was undertaken to examine the fusions in 18 histologically diagnosed IOPNs, including four combined IOPNs. Moreover, in two IOPN cases, invasive carcinomatous lesions were separately examined on their fusion status. Oncocytic thyroidal (n = 10), renal (n = 10), and salivary gland (n = 3) lesions and IPMNs (n = 9)/IPNBs (n = 4) with focal oncocytic changes were examined as controls. Fluorescence in situ hybridization using PRKACA break-apart probes was conducted for the combined IOPN cases. Target sequencing of KRAS exon2/3 and GNAS exon 8/9 was performed for IOPN cases. Fusions were detected in all IOPN cases including invasive lesions/none of the control cases. The fusion event was confirmed also in non-IOPN component in one of the four combined cases. Regarding mutation events, 5.6%/0% of IOPNs were KRAS-mt/GNAS-mt, respectively, and both components of combined IOPNs were all KRAS-wt/GNAS-wt. In conclusion, our study confirmed the sensitivity and specificity of these fusions for IOPNs. Here, we analyzed the roles of these fusion genes in combined IOPNs, proposing the possibility of IOPN development via IPMNs/IPNBs. Further studies with more combined cases are warranted.

Mechanisms of development and progression of pancreatic neoplasms

Pancreatic ductal adenocarcinoma (PDAC) develops via dysplastic changes in the epithelia graded as low- and high-grade with accumulation of molecular alterations. Constitutive activation of mitogen-activated protein kinase (MAPK) contributed by attenuation of DUSP6 plays a key role in sustaining PDAC. Active MAPK induces various molecules that function as effectors to sustain PDAC. AURKA and SON are downstream effectors that contribute substantially to the proliferation and survival of PDAC cells and are potentially useful as therapeutic targets. Active MAPK also promote microRNAs that modulate the proliferation of PDAC cells and are useful as diagnostic markers. Familial pancreatic cancer kindreds in Japan show various germline mutations supposed to increase a pancreatic cancer risk. Intraductal papillary mucinous neoplasms (IPMNs) consist of dilated ducts lined by papillary neoplastic epithelia of various shapes and varying grades of atypia. Various papillae of IPMNs are classified into four subtypes that are associated with clinicopathological features, including patient prognosis. GNAS is a specific driver gene for the development of IPMN through gain-of-function mutations. Tracing of molecular alterations has elucidated the mechanism of progression of IPMN from dysplasia to carcinoma, as well as one type of papillae. Intraductal tubulopapillary neoplasms belong to a distinct class of pancreatic neoplasms.

Carcinoembryonic antigen levels in pancreatic juice are associated with histological subtypes of intraductal papillary mucinous neoplasm of the pancreas

Background

The present study aimed to examine the correlation between preoperative carcinoembryonic antigen levels in pancreatic juice (PJ‐CEA) and the histological subtype of intraductal papillary mucinous neoplasm (IPMN).

Methods

We enrolled IPMN patients who underwent endoscopic retrograde pancreatography between March 2002 and March 2018. Clinical factors associated with IPMN histological subtypes of 67 patients who underwent surgery were analyzed. Furthermore, the relationship between CEA immunohistochemistry findings and histological subtypes was investigated.

Results

Median PJ‐CEA were 15 ng/ml in the gastric type, 150 ng/ml in the intestinal type, and 175 ng/ml in the pancreatobiliary type. Both intestinal and pancreatobiliary types had significantly higher PJ‐CEA than the gastric type (p = 0.001). In the analysis of histological subtype predictors, high PJ‐CEA (≥63 ng/ml) only showed a significant difference in multivariate analyses (95% confidence interval 4.8–70.2; p < 0.001). Immunohistochemistry findings revealed significantly higher CEA expression in the non‐gastric type than in the gastric type (p < 0.001). The non‐gastric type showed a significantly worse prognosis than the gastric type (p = 0.017).

Conclusion

PJ‐CEA was an independent predictor of IPMN histological subtypes in a preoperative setting. High PJ‐CEA predict the non‐gastric type, while low PJ‐CEA predict the gastric type.

Pancreatic Ductal Adenocarcinoma: Molecular Pathology and Predictive Biomarkers

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis due to the lack of methods or biomarkers for early diagnosis and its resistance to conventional treatment modalities, targeted therapies, and immunotherapies. PDACs are a heterogenous group of malignant epithelial neoplasms with various histomorphological patterns and complex, heterogenous genetic/molecular landscapes. The newly proposed molecular classifications of PDAC based on extensive genomic, transcriptomic, proteomic and epigenetic data have provided significant insights into the molecular heterogeneity and aggressive biology of this deadly disease. Recent studies characterizing the tumor microenvironment (TME) have shed light on the dynamic interplays between the tumor cells and the immunosuppressive TME of PDAC, which is essential to disease progression, as well as its resistance to chemotherapy, newly developed targeted therapy and immunotherapy. There is a critical need for the development of predictive markers that can be clinically utilized to select effective personalized therapies for PDAC patients. In this review, we provide an overview of the histological and molecular heterogeneity and subtypes of PDAC, as well as its precursor lesions, immunosuppressive TME, and currently available predictive molecular markers for patients.

Imaging features of intraductal tubulopapillary neoplasm of the pancreas and its differentiation from conventional pancreatic ductal adenocarcinoma

Intraductal tubulopapillary neoplasms (ITPN) are rare pancreatic tumors (< 1% of exocrine neoplasms) and are considered to have better prognosis than classical pancreatic ductal adenocarcinoma (PDAC). The present study aimed to evaluate imaging features of ITPN in computed tomography (CT) and magnetic resonance (MR) imaging. We performed monocentric retrospective analysis of 14 patients with histopathologically verified ITPN, operated in 2003–2018. Images were available for 12 patients and were analysed independently by two radiologists, blinded to reports. Imaging features were compared to a matched control group consisting of 43 patients with PDAC, matched for sex and age. Histopathologic analysis showed invasive carcinoma component in all ITPN patients. CT-attenuation values of ITPN were higher in arterial and venous phases (62.3 ± 14.6 HU and 68 ± 15.6 HU) than in unenhanced phase (39.2 ± 7.9 HU), compatible with solid lesion enhancement. Compared to PDAC, ITPN lesions had significantly higher HU-values in both arterial and venous phases (arterial and venous phases, p < 0.001). ITPN were significantly larger than PDAC (4.1 ± 2.0 cm versus 2.6 ± 0.84 cm, p = 0.021). ITPN lesions were more often well-circumscribed (p < 0.002). Employing a multiple logistic regression analysis with forward stepwise method, higher HU density in the arterial phase (p = 0.012) and well-circumscribed lesion margins (p = 0.047) were found to be significant predictors of ITPN versus PDAC. Our study identified key imaging features for differentiation of ITPN and PDAC. Isodensity or moderate hypodensity and well-circumscribed margins favor the diagnosis of ITPN over PDAC. Being familiar with CT-features of these rare pancreatic tumors is essential for radiologists to accelerate the diagnosis and narrow the differentials.

Integrating Molecular Analysis into the Pathologic Evaluation of Pancreatic Cysts

The development of cross-sectional imaging techniques has enhanced the detection of pancreatic cystic lesions (PCLs). PCLs are found in approximately 2% of the general population, often as incidentally detected lesions on computed tomography or MRI during the evaluation of other medical conditions. Broadly, PCLs are classified as mucinous or nonmucinous. Mucinous PCLs include mucinous cystic neoplasms and intraductal papillary mucinous neoplasms. Nonmucinous PCLs include pseudocysts, serous cystadenomas, solid pseudopapillary neoplasms, and cystic pancreatic neuroendocrine tumors, as well as cystic acinar cell carcinoma, cystic degeneration of pancreatic ductal adenocarcinoma, lymphoepithelial cyst, and others.

Invasive IPMN relapse later and more often in lungs in comparison to pancreatic ductal adenocarcinoma

BACKGROUND

The different oncological outcomes of invasive intraductal papillary mucinous neoplasm (I-IPMN) and pancreatic ductal adenocarcinoma (PDAC) are debated. This study aimed to compare disease recurrence patterns and histopathological characteristics in patients with resected I-IPMN and PDAC.

METHODS

Consecutive patients undergoing surgical resection for stage I-III I-IPMN or PDAC between 2010 and 2016 were retrospectively analyzed. Patients treated with neoadjuvant therapy or resected for Tis neoplasia were excluded. All surgical specimens were re-staged according to AJCC-8th-edition.

RESULTS

A total of 330 patients were included, of whom 43 had I-IPMN and 287 had PDAC. Median follow-up time was 26.7 (1.3-92.3) months and estimated median disease-free survival (DFS) was 60.3 months (47.2-73.4) for I-IPMN and 23.8 (19.3-28.2) months for PDAC (p < 0.001). During follow-up, 32.6% of I-IPMN and 67.9% of PDAC patients experienced recurrence (p < 0.001). The sites of first recurrence were the lungs (38.5% vs 13.1%, p = 0.027), liver (28.6% vs 45.0%, p = 0.180) and local (15.4% vs 36.6%, p = 0.101) for I-IPMN and PDAC, respectively. At multivariate analysis, I-IPMN histology remained an independent predictive factor for longer DFS (OR 0.528, CI 95% 0.278-1.000, p = 0.050), regardless of stage or adjuvant chemotherapy. I-IPMN and PDAC differed in rates of neuroinvasion (51.2% vs 97.2%) and positive lymph node status (N+) (46.5% vs 82.7%), especially in patients with lower T status.

CONCLUSION

I-IPMN showed a different recurrence pattern compared to PDAC, with a higher lung tropism, and longer DFS. This different biological behavior is associated with lower rates of neuroinvasion and nodal involvement, especially in early-stage disease.

Pancreatic Cancer: Pathogenesis, Screening, Diagnosis, and Treatment

Pancreatic ductal adenocarcinoma (PDAC) is a clinically challenging cancer, due to both its late stage at diagnosis and its resistance to chemotherapy. However, recent advances in our understanding of the biology of PDAC have revealed new opportunities for early detection and targeted therapy of PDAC. In this review, we discuss the pathogenesis of PDAC, including molecular alterations in tumor cells, cellular alterations in the tumor microenvironment, and population-level risk factors. We review the current status of surveillance and early detection of PDAC, including populations at high risk and screening approaches. We outline the diagnostic approach to PDAC and highlight key treatment considerations, including how therapeutic approaches change with disease stage and targetable subtypes of PDAC. Recent years have seen significant improvements in our approaches to detect and treat PDAC, but large-scale, coordinated efforts will be needed to maximize the clinical impact for patients and improve overall survival.

Current Pathology Model of Pancreatic Cancer

Pancreatic cancer (PC) is one of the most aggressive and lethal malignant neoplasms, ranking in seventh place in the world in terms of the incidence of death, with overall 5-year survival rates still below 10%. The knowledge about PC pathomechanisms is rapidly expanding. Daily reports reveal new aspects of tumor biology, including its molecular and morphological heterogeneity, explain complicated "cross-talk" that happens between the cancer cells and tumor stroma, or the nature of the PC-associated neural remodeling (PANR). Staying up-to-date is hard and crucial at the same time. In this review, we are focusing on a comprehensive summary of PC aspects that are important in pathologic reporting, impact patients' outcomes, and bring meaningful information for clinicians. Finally, we show promising new trends in diagnostic technologies that might bring a difference in PC early diagnosis.

MNX1-HNF1B Axis Is Indispensable for Intraductal Papillary Mucinous Neoplasm Lineages

BACKGROUND & AIMS

Chromatin architecture governs cell lineages by regulating the specific gene expression; however, its role in the diversity of cancer development remains unknown. Among pancreatic cancers, pancreatic ductal adenocarcinoma (PDAC) and intraductal papillary mucinous neoplasms (IPMN) with an associated invasive carcinoma (IPMNinv) arise from 2 distinct precursors, and their fundamental differences remain obscure. Here, we aimed to assess the difference of chromatin architecture regulating the transcriptional signatures or biological features in pancreatic cancers.

METHODS

We established 28 human organoids from distinct subtypes of pancreatic tumors, including IPMN, IPMNinv, and PDAC. We performed exome sequencing (seq), RNA-seq, assay for transposase-accessible chromatin-seq, chromatin immunoprecipitation-seq, high-throughput chromosome conformation capture, and phenotypic analyses with short hairpin RNA or clustered regularly interspaced short palindromic repeats interference.

RESULTS

Established organoids successfully reproduced the histology of primary tumors. IPMN and IPMNinv organoids harbored GNAS, RNF43, or KLF4 mutations and showed the distinct expression profiles compared with PDAC. Chromatin accessibility profiles revealed the gain of stomach-specific open regions in IPMN and the pattern of diverse gastrointestinal tissues in IPMNinv. In contrast, PDAC presented an impressive loss of accessible regions compared with normal pancreatic ducts. Transcription factor footprint analysis and functional assays identified that MNX1 and HNF1B were biologically indispensable for IPMN lineages. The upregulation of MNX1 was specifically marked in the human IPMN lineage tissues. The MNX1-HNF1B axis governed a set of genes, including MYC, SOX9, and OLFM4, which are known to be essential for gastrointestinal stem cells. High-throughput chromosome conformation capture analysis suggested the HNF1B target genes to be 3-dimensionally connected in the genome of IPMNinv.

CONCLUSIONS

Our organoid analyses identified the MNX1-HNF1B axis to be biologically significant in IPMN lineages.

Molecular signaling in pancreatic ductal metaplasia: emerging biomarkers for detection and intervention of early pancreatic cancer

Pancreatic ductal metaplasia (PDM) is the transformation of potentially various types of cells in the pancreas into ductal or ductal-like cells, which eventually replace the existing differentiated somatic cell type(s). PDM is usually triggered by and manifests its ability to adapt to environmental stimuli and genetic insults. The development of PDM to atypical hyperplasia or dysplasia is an important risk factor for pancreatic intraepithelial neoplasia (PanIN) and pancreatic ductal adenocarcinoma (PDA). Recent studies using genetically engineered mouse models, cell lineage tracing, single-cell sequencing and others have unraveled novel cellular and molecular insights in PDM formation and evolution. Those novel findings help better understand the cellular origins and functional significance of PDM and its regulation at cellular and molecular levels. Given that PDM represents the earliest pathological changes in PDA initiation and development, translational studies are beginning to define PDM-associated cell and molecular biomarkers that can be used to screen and detect early PDA and to enable its effective intervention, thereby truly and significantly reducing the dreadful mortality rate of PDA. This review will describe recent advances in the understanding of PDM biology with a focus on its underlying cellular and molecular mechanisms, and in biomarker discovery with clinical implications for the management of pancreatic regeneration and tumorigenesis.

Updates in the Diagnosis of Intraductal Neoplasms of the Pancreas

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest types of cancer worldwide. There are many reasons for this dismal prognosis, including the advanced stage at the time of diagnosis and the lack of effective therapeutic approaches. Intraductal papillary mucinous neoplasms (IPMNs) represent detectable and treatable precursor lesions of PDAC. Our understanding of the pathology of IPMNs has evolved over the past few decades, and new advances in diagnostic tools have emerged. The new World Health Organization (WHO) classification scheme now recognizes the previously considered variants of IPMNs, such as intraductal oncocytic papillary neoplasms (IOPNs) and intraductal tubulopapillary neoplasms (ITPNs), as distinct neoplasms. New imaging and molecular diagnostic tests are being developed to recognize these PDAC precursor lesions better. Here, we review the advances in diagnostic tools for IPMNs, IOPNs, and ITPNs, emphasizing the new (5th edition, 2019) WHO classification for pathological diagnosis, molecular markers, new laboratory tests, and imaging tools.

A Review of Mucinous Cystic and Intraductal Neoplasms of the Pancreatobiliary Tract

CONTEXT.—

Although most pancreatic and bile duct neoplasms are solid, mucinous cystic neoplasms and intraductal neoplasms have been increasingly recognized even when clinically silent, thanks to the increased use of sensitive imaging techniques. Cystic and intraductal neoplasms of the pancreas are often resectable and curable and constitute about 5% of all pancreatic neoplasms. Owing to their preinvasive nature and different biology, recognition of these entities remains a major priority. Mucinous cystic neoplasms are histologically and clinically distinct from other cystic pancreatic neoplasms. Pancreatic intraductal neoplasms encompass 3 major entities: intraductal papillary mucinous neoplasm, intraductal oncocytic papillary neoplasm, and intraductal tubulopapillary neoplasm. Intraductal papillary neoplasms of bile ducts are also preinvasive mass-forming neoplasms with both similarities and differences with their pancreatic counterparts. All of these pancreatobiliary neoplasms have diverse and distinctive clinicopathologic, genetic, and prognostic variations.

OBJECTIVE.—

To review the clinical, pathologic, and molecular features of mucinous cystic and intraductal neoplasms of the pancreatobiliary tract.

DATA SOURCES.—

Literature review, diagnostic manuals, and guidelines.

CONCLUSIONS.—

This review will briefly describe well-known clinical and pathologic features and will focus on selected recently described aspects of morphology, grading, classification, and genomic alterations of cystic and intraductal neoplasms of the pancreatobiliary tract.

Genetic Mutations of Pancreatic Cancer and Genetically Engineered Mouse Models

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy. Recent multi-gene analysis approaches such as next-generation sequencing have provided useful information on the molecular characterization of pancreatic tumors. Different types of pancreatic cancer and precursor lesions are characterized by specific molecular alterations. Genetically engineered mouse models (GEMMs) of PDAC are useful tools to understand the roles of altered genes. Most GEMMs are driven by oncogenic Kras, and can recapitulate the histological and molecular hallmarks of human PDAC and comparable precursor lesions. In this review, we summarize the main molecular alterations found in pancreatic neoplasms and GEMMs developed based on these alterations.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy, and the seventh leading cause of cancer-related deaths worldwide. An improved understanding of tumor biology and novel therapeutic discoveries are needed to improve overall survival. Recent multi-gene analysis approaches such as next-generation sequencing have provided useful information on the molecular characterization of pancreatic tumors. Different types of pancreatic cancer and precursor lesions are characterized by specific molecular alterations. Genetically engineered mouse models (GEMMs) of PDAC are useful to understand the roles of altered genes. Most GEMMs are driven by oncogenic Kras, and can recapitulate the histological and molecular hallmarks of human PDAC and comparable precursor lesions. Advanced GEMMs permit the temporally and spatially controlled manipulation of multiple target genes using a dual-recombinase system or CRISPR/Cas9 gene editing. GEMMs that express fluorescent proteins allow cell lineage tracing to follow tumor growth and metastasis to understand the contribution of different cell types in cancer progression. GEMMs are widely used for therapeutic optimization. In this review, we summarize the main molecular alterations found in pancreatic neoplasms, developed GEMMs, and the contribution of GEMMs to the current understanding of PDAC pathobiology. Furthermore, we attempted to modify the categorization of altered driver genes according to the most updated findings.