IPMNs with co-occurring invasive cancers: neighbours but not always relatives

Molecular heterogeneity of pancreatic intraductal papillary mucinous neoplasms and implications for novel endoscopic tissue sampling strategies

AIMS

Intraductal papillary mucinous neoplasms (IPMNs) may be precursor lesions of pancreatic cancer. The path towards malignancy is associated with mutations in tumour suppressor-and oncogenes that may serve as biomarkers during diagnostic investigation. A novel micro forceps has made it possible to obtain biopsies from the cyst wall for analysis by next generation sequencing (NGS), providing an opportunity for early detection and intervention. However, the impact of spatial tumour heterogeneity on the representability of the biopsies has not been determined. The primary aim is to characterise the impact of molecular heterogeneity of the luminal cyst wall on tissue sampling strategies with small biopsies.

METHODS

We performed NGS and immunohistochemical phenotyping on 18 resected IPMNs with varying degrees of dysplasia and for a subset, concomitant carcinoma, using a commercially available NGS-panel of 51 oncogenes. We simulated endoscopic biopsies by performing punch biopsies (PBs) of the cyst wall from resected specimens.

RESULTS

In total, 127 NGS analyses were performed. Concomitant KRAS and GNAS was a common feature of the IPMNs. Mutations in KRAS and GNAS were associated with low-grade dysplasia whereas alterations in TP53, SMAD4, CDKN2A and PIK3CA were associated with high-grade dysplasia and/or carcinoma. The mutational analysis of the PBs from the cyst wall was compared with the whole lesion. No difference was detected between PBs and whole lesions when the cumulated mutational profile in increasing order of randomly performed PBs was compared.

CONCLUSIONS

Small IPMN biopsies from the cyst wall are adequate to yield a molecular diagnosis.

Multiregion whole-exome sequencing of intraductal papillary mucinous neoplasms reveals frequent somatic KLF4 mutations predominantly in low-grade regions

OBJECTIVE

Intraductal papillary mucinous neoplasms (IPMNs) are non-invasive precursor lesions that can progress to invasive pancreatic cancer and are classified as low-grade or high-grade based on the morphology of the neoplastic epithelium. We aimed to compare genetic alterations in low-grade and high-grade regions of the same IPMN in order to identify molecular alterations underlying neoplastic progression.

DESIGN

We performed multiregion whole exome sequencing on tissue samples from 17 IPMNs with both low-grade and high-grade dysplasia (76 IPMN regions, including 49 from low-grade dysplasia and 27 from high-grade dysplasia). We reconstructed the phylogeny for each case, and we assessed mutations in a novel driver gene in an independent cohort of 63 IPMN cyst fluid samples.

RESULTS

Our multiregion whole exome sequencing identified KLF4, a previously unreported genetic driver of IPMN tumorigenesis, with hotspot mutations in one of two codons identified in >50% of the analyzed IPMNs. Mutations in KLF4 were significantly more prevalent in low-grade regions in our sequenced cases. Phylogenetic analyses of whole exome sequencing data demonstrated diverse patterns of IPMN initiation and progression. Hotspot mutations in KLF4 were also identified in an independent cohort of IPMN cyst fluid samples, again with a significantly higher prevalence in low-grade IPMNs.

CONCLUSION

Hotspot mutations in KLF4 occur at high prevalence in IPMNs. Unique among pancreatic driver genes, KLF4 mutations are enriched in low-grade IPMNs. These data highlight distinct molecular features of low-grade and high-grade dysplasia and suggest diverse pathways to high-grade dysplasia via the IPMN pathway.

ABO Blood Group and Risk of Pancreatic Carcinogenesis in Intraductal Papillary Mucinous Neoplasms

BACKGROUND

ABO blood group has been associated with risks of various malignancies, including pancreatic cancer. No study has evaluated the association of ABO blood group with incidence of pancreatic carcinogenesis during follow-up of patients with intraductal papillary mucinous neoplasms (IPMN).

METHODS

Among 3,164 patients diagnosed with pancreatic cysts at the University of Tokyo (Tokyo, Japan) from 1994 through 2019, we identified 1,815 patients with IPMN with available data on ABO blood group. We studied the association of ABO blood group with incidence of pancreatic carcinoma, overall and by carcinoma types [IPMN-derived carcinoma or concomitant pancreatic ductal adenocarcinoma (PDAC)]. Utilizing competing-risks proportional hazards models, we estimated subdistribution hazard ratios (SHR) for incidence of pancreatic carcinoma with adjustment for potential confounders, including cyst characteristics.

RESULTS

During 11,518 person-years of follow-up, we identified 97 patients diagnosed with pancreatic carcinoma (53 with IPMN-derived carcinoma and 44 with concomitant PDAC). Compared with patients with blood group O, patients with blood groups A, B, and AB had multivariable SHRs (95% confidence intervals) for pancreatic carcinoma of 2.25 (1.25-4.07; P = 0.007), 2.09 (1.08-4.05; P = 0.028), and 1.17 (0.43-3.19; P = 0.76), respectively. We observed no differential association of ABO blood group with pancreatic carcinoma incidence by carcinoma types.

CONCLUSIONS

In this large long-term study, patients with IPMN with blood group A or B appeared to be at higher risk of pancreatic carcinoma compared with those with blood group O.

IMPACT

ABO blood group can be a biomarker for pancreatic cancer risk among patients with IPMNs.

Histopathological evaluation of resected intraductal papillary mucinous neoplasms reveals distinct patterns of invasion in associated carcinomas

Invasive intraductal papillary mucinous neoplasms (inv-IPMNs) have a better prognosis than regular pancreatic ductal adenocarcinoma (PDAC), but no association with status of surgical margins and microscopic infiltration patterns has previously been described. The aim of this study is to review patterns of invasion and the predictive value of clinical guidelines in terms of rates of resection of high-grade dysplasia (HGD) and cancer among intraductal papillary mucinous neoplasms (IPMNs). Consecutively, resected IPMNs between 2011 and 2017 were analyzed. Data were obtained from a prospectively maintained database. A total of 132 patients were identified. Out of these, 38 patients with inv-IPMNs, initially identified as solid lesions suspicious of cancer, were compared with a control group of 101 patients with ordinary PDAC. Lower rates of vascular invasion, perineural invasion, lymph node metastasis, advanced T stage, and R1 status were characteristic of the inv-IPMNs in addition to better overall survival (OS) for a low tumor stage. Furthermore, as novel findings, the PDACs presented with resection margin involvement of 3 or more positive margins (31.3% vs. 9.5%, p = 0.044), associated with poor OS. Of the patients presenting as pT3, the inv-IPMN less often invaded more than one extrapancreatic anatomical structure (40.1% vs. 63.9%, p = 0.03). Regarding the predictive value of clinical guidelines, the frequency of resected HGD in IPMNs with high-risk stigmata (n = 54) and IPMNs with worrisome features was 30.7%, and the frequency of invasive carcinoma was 5.7%. In conclusion, we report a low resection rate of high-risk IPMNs and present novel findings describing inv-IPMNs as a less infiltrative phenotype compared with regular PDAC.

Guidelines on management of pancreatic cysts detected in high-risk individuals: An evaluation of the 2017 Fukuoka guidelines and the 2020 International Cancer of the Pancreas Screening (CAPS) consortium statements

BACKGROUND

Objectives: Pancreatic cysts are frequently detected in high-risk individuals (HRI) undergoing surveillance for pancreatic cancer. The International Cancer of the Pancreas Screening (CAPS) Consortium developed consensus recommendations for surgical resection of pancreatic cysts in HRI that are similar to the Fukuoka guidelines used for the management of sporadic cysts. We compared the performance characteristics of CAPS criteria for pancreatic cyst management in HRI with the Fukuoka guidelines originally designed for the management of cysts in non-HRI.

METHODS

Using prospectively collected data from CAPS studies, we determined for each patient with resected screen-detected cyst(s) whether Fukuoka guidelines or CAPS consensus statements would have recommended surgery. We compared sensitivity, specificity, PPV, NPV, and Receiver Operator Characteristics (ROC) curves of these guidelines at predicting the presence of high-grade dysplasia or invasive cancer in pancreatic cysts.

RESULTS

356/732 HRI had ≥ one pancreatic cyst detected; 24 had surgery for concerning cystic lesions. The sensitivity, specificity, PPV, and NPV for the Fukuoka criteria were 40%, 85%, 40%, and 85%, while those of the CAPS criteria were 60%, 85%, 50%, 89%, respectively. ROC curve analyses showed no significant difference between the Fukuoka and CAPS criteria.

CONCLUSIONS

In HRI, the CAPS and Fukuoka criteria are moderately specific, but not sufficiently sensitive for detecting advanced neoplasia in cystic lesions. New approaches are needed to guide the surgical management of cystic lesions in HRI.

Prevalence and Risk Factors for Intraductal Papillary Mucinous Neoplasm in Patients With Chronic Kidney Disease: A Single-Center Case-Control Study

OBJECTIVES

The exact prevalence for intraductal papillary mucinous neoplasm (IPMN) in patients with chronic kidney disease (CKD) remains unknown. In this single-center case-control study, we aimed to study the prevalence and risk factors for IPMN in patients with CKD.

METHODS

We performed a retrospective case-control study comparing patients with and without CKD who had magnetic resonance imaging of the abdomen performed between January 2018 and December 2018. Patient demographic, clinical, and imaging metrics were extracted from chart review. The prevalence of IPMN was compared between the 2 groups.

RESULTS

A total of 800 patient charts were reviewed. There were 400 patients with CKD compared with an age-matched control group of 400 patients without CKD. The total prevalence of IPMN in patients with CKD was 13.7% (55/400) compared with 7.8% (29/400; P = 0.002) in non-CKD patients. The prevalence of diabetes mellitus was significantly higher in the CKD group (41% vs 14%, P = 0.0001). The percentage of patients consuming alcohol was significantly higher in the non-CKD group (23% vs 35%, P = 0.002).

CONCLUSIONS

Patients with CKD have a significantly higher prevalence of IPMN compared with non-CKD patients. Larger population-based studies are needed to confirm these findings.

Pancreatic cancer pathology viewed in the light of evolution

One way to understand ductal adenocarcinoma of the pancreas (pancreatic cancer) is to view it as unimaginably large numbers of evolving living organisms interacting with their environment. This “evolutionary view” creates both expected and surprising perspectives in all stages of neoplastic progression. Advances in the field will require greater attention to this critical evolutionary prospective.

The genetics of ductal adenocarcinoma of the pancreas in the year 2020: dramatic progress, but far to go

The publication of the "Pan-Cancer Atlas" by the Pan-Cancer Analysis of Whole Genomes Consortium, a partnership formed by The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC), provides a wonderful opportunity to reflect on where we stand in our understanding of the genetics of pancreatic cancer, as well as on the opportunities to translate this understanding to patient care. From germline variants that predispose to the development of pancreatic cancer, to somatic mutations that are therapeutically targetable, genetics is now providing hope, where there once was no hope, for those diagnosed with pancreatic cancer.

Morphologic and Molecular Landscape of Pancreatic Cancer Variants as the Basis of New Therapeutic Strategies for Precision Oncology

To date, pancreatic cancer is still one of the most lethal cancers in the world, mainly due to the lack of early diagnosis and personalized treatment strategies. In this context, the possibility and the opportunity of identifying genetic and molecular biomarkers are crucial to improve the feasibility of precision medicine. In 2019, the World Health Organization classified pancreatic ductal adenocarcinoma cancer (the most common pancreatic tumor type) into eight variants, according to specific histomorphological features. They are: colloid carcinoma, medullary carcinoma, adenosquamous carcinoma, undifferentiated carcinoma, including also rhabdoid carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, hepatoid carcinoma, and signet-ring/poorly cohesive cells carcinoma. Interestingly, despite the very low incidence of these variants, innovative high throughput genomic/transcriptomic techniques allowed the investigation of both somatic and germline mutations in each specific variant, paving the way for their possible classification according also to specific alterations, along with the canonical mutations of pancreatic cancer (KRAS, TP53, CDKN2A, SMAD4). In this review, we aim to report the current evidence about genetic/molecular profiles of pancreatic cancer variants, highlighting their role in therapeutic and clinical impact.

The Impact of Clinical and Pathological Features on Intraductal Papillary Mucinous Neoplasm Recurrence After Surgical Resection: Long-Term Follow-Up Analysis

OBJECTIVE

This study aimed to identify risk factors for recurrence after pancreatic resection for intraductal papillary mucinous neoplasm (IPMN).

SUMMARY BACKGROUND DATA

Long-term follow-up data on recurrence after surgical resection for IPMN are currently lacking. Previous studies have presented mixed results on the role of margin status in risk of recurrence after surgical resection.

METHODS

A total of 126 patients that underwent resection for noninvasive IPMN were followed for a median of 9.5 years. Dedicated pathological and radiological reviews were performed to correlate clinical and pathological features (including detailed pathological features of the parenchymal margin) with recurrence after surgical resection. In addition, in a subset of 32 patients with positive margins, we determined the relationship between the margin and original IPMN using driver gene mutations identified by next-generation sequencing.

RESULTS

Family history of pancreatic cancer and high-grade IPMN was identified as risk factors for recurrence in both uni- and multivariate analysis (adjusted hazard ratio 3.05 and 1.88, respectively). Although positive margin was not significantly associated with recurrence in our cohort, the size and grade of the dysplastic focus at the margin were significantly correlated with recurrence in margin-positive patients. Genetic analyses showed that the neoplastic epithelium at the margin was independent from the original IPMN in at least 9 of 32 cases (28%). The majority of recurrences (74%) occurred after 3 years, and a significant minority (32%) occurred after 5 years.

CONCLUSION

Sustained postoperative surveillance for all patients is indicated, particularly those with risk factors such has family history and high-grade dysplasia.

Molecular characterization of organoids derived from pancreatic intraductal papillary mucinous neoplasms

Intraductal papillary mucinous neoplasms (IPMNs) are commonly identified non-invasive cyst-forming pancreatic neoplasms with the potential to progress into invasive pancreatic adenocarcinoma. There are few in vitro models with which to study the biology of IPMNs and their progression to invasive carcinoma. Therefore, we generated a living biobank of organoids from seven normal pancreatic ducts and ten IPMNs. We characterized eight IPMN organoid samples using whole genome sequencing and characterized five IPMN organoids and seven normal pancreatic duct organoids using transcriptome sequencing. We identified an average of 11,344 somatic mutations in the genomes of organoids derived from IPMNs, with one sample harboring 61,537 somatic mutations enriched for T→C transitions and T→A transversions. Recurrent coding somatic mutations were identified in 15 genes, including KRAS, GNAS, RNF43, PHF3, and RBM10. The most frequently mutated genes were KRAS, GNAS, and RNF43, with somatic mutations identified in six (75%), four (50%), and three (37.5%) IPMN organoid samples, respectively. On average, we identified 36 structural variants in IPMN derived organoids, and none had an unstable phenotype (> 200 structural variants). Transcriptome sequencing identified 28 genes differentially expressed between normal pancreatic duct organoid and IPMN organoid samples. The most significantly upregulated and downregulated genes were CLDN18 and FOXA1. Immunohistochemical analysis of FOXA1 expression in 112 IPMNs, 113 mucinous cystic neoplasms, and 145 pancreatic ductal adenocarcinomas demonstrated statistically significant loss of expression in low-grade IPMNs (p < 0.0016), mucinous cystic neoplasms (p < 0.0001), and pancreatic ductal adenocarcinoma of any histologic grade (p < 0.0001) compared to normal pancreatic ducts. These data indicate that FOXA1 loss of expression occurs early in pancreatic tumorigenesis. Our study highlights the utility of organoid culture to study the genetics and biology of normal pancreatic duct and IPMNs. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Malignant epithelial/exocrine tumors of the pancreas

Pancreatic malignant exocrine tumors represent the most important cause of cancer-related death for pancreatic neoplasms. The most common tumor type in this category is represented by pancreatic ductal adenocarcinoma (PDAC), an ill defined, stroma-rich, scirrhous neoplasm with glandular differentiation. Here we present the relevant characteristics of the most important PDAC variants, namely adenosquamous carcinoma, colloid carcinoma, undifferentiated carcinoma, undifferentiated carcinoma with osteoclast-like giant cells, signet ring carcinoma, medullary carcinoma and hepatoid carcinoma. The other categories of malignant exocrine tumors, characterized by fleshy, stroma-poor, circumscribed neoplasms, include acinar cell carcinoma (pure and mixed), pancreatoblastoma, and solid pseudopapillary neoplasms. The most important macroscopic, histologic, immunohistochemical and molecular hallmarks of all these tumors, highlighting their key diagnostic/pathological features are presented. Lastly, standardized indications regarding gross sampling and how to compile a formal pathology report for pancreatic malignant exocrine tumors will be provided.

Genomic characterization of malignant progression in neoplastic pancreatic cysts

Intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs) are non-invasive neoplasms that are often observed in association with invasive pancreatic cancers, but their origins and evolutionary relationships are poorly understood. In this study, we analyze 148 samples from IPMNs, MCNs, and small associated invasive carcinomas from 18 patients using whole exome or targeted sequencing. Using evolutionary analyses, we establish that both IPMNs and MCNs are direct precursors to pancreatic cancer. Mutations in SMAD4 and TGFBR2 are frequently restricted to invasive carcinoma, while RNF43 alterations are largely in non-invasive lesions. Genomic analyses suggest an average window of over three years between the development of high-grade dysplasia and pancreatic cancer. Taken together, these data establish non-invasive IPMNs and MCNs as origins of invasive pancreatic cancer, identifying potential drivers of invasion, highlighting the complex clonal dynamics prior to malignant transformation, and providing opportunities for early detection and intervention.

Impact of adjuvant therapy in patients with invasive intraductal papillary mucinous neoplasms of the pancreas

BACKGROUND

There is limited data on the efficacy of adjuvant therapy (AT) in patients with invasive intraductal papillary mucinous neoplasms of the pancreas (IPMN). This single center retrospective cohort study aims to assess the impact of AT on survival in these patients.

METHODS

Patients undergoing surgery for invasive IPMN between 1993 and 2018 were included in the study. We compared the clinicopathologic features and evaluated overall survival (OS) using multivariate Cox regression adjusting for adjuvant therapy, age, T and N stage, perineural and lymphovascular invasion. We also assessed survival differences between surgery alone and AT in node negative (N0) and node positive (N+) subgroups.

RESULTS

103 patients were included in the study; 69 underwent surgery alone while 34 also received AT. Patients in the AT group were significantly younger, presented at higher T and N stages and had more perineural and lymphovascular invasion. Median OS in the surgery alone group was 134 months and 65 months in the AT group, p = 0.052. On multivariate analysis, AT was not associated with improved OS; hazard ratio (HR) = 1.03 (0.52-2.05). In N0 patients, compared to surgery alone, AT was associated with a worse median OS (65 vs 167 months, p = 0.03), whereas in N+ patients there was a non-significant improvement (50.5 vs 20.4 months, p = 0.315).

CONCLUSION

AT did not improve survival in the overall cohort even after multivariate analysis. N0 patients have excellent survival, and AT should probably be avoided in them, whereas it may be considered in patients with N+ disease.

Proteomic Profiling of Small Extracellular Vesicles Secreted by Human Pancreatic Cancer Cells Implicated in Cellular Transformation

Extracellular vesicles secreted from tumor cells are functional vehicles capable of contributing to intercellular communication and metastasis. A growing number of studies have focused on elucidating the role that tumor-derived extracellular vesicles play in spreading pancreatic cancer to other organs, due to the highly metastatic nature of the disease. We recently showed that small extracellular vesicles secreted from pancreatic cancer cells could initiate malignant transformation of healthy cells. Here, we analyzed the protein cargo contained within these vesicles using mass spectrometry-based proteomics to better understand their makeup and biological characteristics. Three different human pancreatic cancer cell lines were compared to normal pancreatic epithelial cells revealing distinct differences in protein cargo between cancer and normal vesicles. Vesicles from cancer cells contain an enrichment of proteins that function in the endosomal compartment of cells responsible for vesicle formation and secretion in addition to proteins that have been shown to contribute to oncogenic cell transformation. Conversely, vesicles from normal pancreatic cells were shown to be enriched for immune response proteins. Collectively, results contribute to what we know about the cargo contained within or excluded from cancer cell-derived extracellular vesicles, supporting their role in biological processes including metastasis and cancer progression.

Exosomal miRNA signatures of pancreatic lesions

BACKGROUND

Pancreatic and peri-pancreatic neoplasms encompass a variety of histotypes characterized by a heterogeneous prognostic impact. miRNAs are considered efficient candidate biomarkers due to their high stability in tissues and body fluids. We applied Nanostring profiling of circulating exosomal miRNAs to distinct pancreatic lesions in order to establish a source for biomarker development.

METHODS

A series of 140 plasma samples obtained from patients affected by pancreatic ductal adenocarcinoma (PDAC, n = 58), pancreatic neuroendocrine tumors (PanNET, n = 42), intraductal papillary mucinous neoplasms (IPMN, n = 20), and ampulla of Vater carcinomas (AVC, n = 20) were analyzed. Comprehensive miRNA profiling was performed on plasma-derived exosomes. Relevant miRNAs were validated by qRT-PCR and in situ hybridization (ISH).

RESULTS

Lesion specific miRNAs were identified through multiple disease comparisons. Selected miRNAs were validated in the plasma by qRT-PCR and at tissue level by ISH. We leveraged the presence of clinical subtypes with each disease cohort to identify miRNAs that are differentially enriched in aggressive phenotypes.

CONCLUSIONS

This study shows that pancreatic lesions are characterized by specific exosomal-miRNA signatures. We also provide the basis for further explorations in order to better understand the relevance of these signatures in pancreatic neoplasms.

Metachronous intraductal papillary mucinous neoplasms disseminate via the pancreatic duct following resection

Metachronous development of intraductal papillary mucinous neoplasms in the remnant pancreas following resection is a significant clinical burden. Our aim was to characterize the clinicopathological and molecular features of the patients with metachronous tumor development to identify predictive factors and the possible route(s) of dissemination. Seventy-four patients who underwent resection of intraductal papillary mucinous neoplasms with no invasive compartment or associated carcinoma were retrospectively analyzed. In patients with metachronous tumor development, targeted sequencing of 18 genes associated with pancreatic tumorigenesis and immunohistochemical detection of four proteins (p53, SMAD4, p16, and β-catenin) were performed on both primary and metachronous tumors. The distributions of microscopic neoplastic lesions were examined at surgical margins and in apparently normal tissue apart from the primary tumor. During the median follow-up period of 52 months, 9 patients (12%) developed metachronous tumors in the remnant pancreas. Primary tumors located in the body/tail of the pancreas (odds ratio, 15; 95% confidence interval, 1.6-131) and of the pancreatobiliary type (odds ratio, 6.1; 95% confidence interval, 1.1-35.7) were identified as significant risk factors for subsequent metachronous tumor development. Eight of the nine patients shared molecular aberrations between their primary and metachronous tumors, suggesting migrations from the primary tumor to the pancreatic duct as the cause of metachronous tumor development. Our data suggest that these post-resection metachronous tumors develop by skip dissemination of the primary tumor, potentially via the pancreatic duct. The development of strategies to better predict and prevent this form of tumor progression is necessary.

Detection of Circulating Tumor DNA in Patients with Pancreatic Cancer Using Digital Next-Generation Sequencing

Circulating tumor DNA (ctDNA) measurements can be used to estimate tumor burden, but avoiding false-positive results is challenging. Herein, digital next-generation sequencing (NGS) is evaluated as a ctDNA detection method. Plasma KRAS and GNAS hotspot mutation levels were measured in 140 subjects, including 67 with pancreatic ductal adenocarcinoma and 73 healthy and disease controls. To limit chemical modifications of DNA that yield false-positive mutation calls, plasma DNA was enzymatically pretreated, after which DNA was aliquoted for digital detection of mutations (up to 384 aliquots/sample) by PCR and NGS. A digital NGS score of two SDs above the mean in controls was considered positive. Thirty-seven percent of patients with pancreatic cancer, including 31% of patients with stages I/II disease, had positive KRAS codon 12 ctDNA scores; only one patient had a positive GNAS mutation score. Two disease control patients had positive ctDNA scores. Low-normal-range digital NGS scores at mutation hotspots were found at similar levels in healthy and disease controls, usually at sites of cytosine deamination, and were likely the result of chemical modification of plasma DNA and NGS error rather than true mutations. Digital NGS detects mutated ctDNA in patients with pancreatic cancer with similar yield to other methods. Detection of low-level, true-positive ctDNA is limited by frequent low-level detection of false-positive mutation calls in plasma DNA from controls.

Invasive Intraductal Papillary Mucinous Neoplasms: CT Features of Colloid Carcinoma Versus Tubular Adenocarcinoma of the Pancreas

OBJECTIVE. The purpose of this study is to compare the CT features of colloid carcinoma and tubular adenocarcinoma of the pancreas arising in association with intraductal papillary mucinous neoplasms (IPMNs). MATERIALS AND METHODS. The preoperative CT images of 85 patients with histopathologically proven IPMNs and associated invasive adenocarcinoma located next to each other were retrospectively reviewed. Twenty-nine patients (34.1%; 19 men and 10 women; mean [± SD] age, 68.0 ± 9.5 years) had invasive colloid carcinoma, and 56 patients (65.9%; 31 men and 25 women; mean age, 70.8 ± 10.6 years) had invasive tubular adenocarcinoma. We compared the following CT features between the two groups: IPMN type, main pancreatic duct (MPD) and common bile duct diameters, diameter and characteristics of the largest cystic lesion for branch duct and mixed-type IPMNs, presence of an extracystic or extraductal solid mass next to the cystic lesion or MPD, morphologic features of the upstream MPD in relation to the cystic lesion or solid mass, and presence of a fistula to the adjacent organs. RESULTS. An MPD size of 9.5 mm or greater, a largest cystic lesion diameter of 28 mm or greater, location in the head or neck, septation, calcification, presence of a mural nodule(s) within a cystic lesion or MPD, and presence of a fistula were all more commonly associated with colloid carcinoma. In contrast, presence of an extracystic or extraductal solid mass and an abrupt change in the caliber of the dilated MPD were associated with tubular adenocarcinoma. The best CT feature for differentiating between the two groups was the morphologic features of the upstream MPD in relation to the cystic lesion or solid mass (sensitivity, 81.3%; specificity, 92.3%). CONCLUSION. Preoperative CT is helpful in differentiating two types of invasive carcinoma arising in association with IPMNs. These findings are clinically important because prognosis is better for colloid carcinoma than for tubular adenocarcinoma.

Long-term Risk of Malignancy in Branch-Duct Intraductal Papillary Mucinous Neoplasms

BACKGROUND & AIMS

Long-term outcomes of patients with branch-duct intraductal papillary mucinous neoplasms (IPMNs), particularly those after 5 years of surveillance, have not been fully evaluated in large studies. We analyzed incidences of IPMN-derived carcinoma and concomitant ductal adenocarcinoma (pancreatic ductal adenocarcinoma [PDAC]) over 20 years in a large population of patients.

METHODS

We identified 1404 consecutive patients (52% women; mean age, 67.5 years) with a diagnosis of branch-duct IPMN, from 1994 through 2017, at the University of Tokyo in Japan. Using a competing risk analysis, we estimated cumulative incidence of pancreatic carcinoma, overall and by carcinoma type. We used competing risks proportional hazards models to estimate subdistribution hazard ratios (SHRs) for incidences of carcinomas. To differentiate IPMN-derived and concomitant carcinomas, we collected genomic DNA from available paired samples of IPMNs and carcinomas and detected mutations in GNAS and KRAS by polymerase chain reaction and pyrosequencing.

RESULTS

During 9231 person-years of follow-up, we identified 68 patients with pancreatic carcinomas (38 patients with IPMN-derived carcinomas and 30 patients with concomitant PDACs); the overall incidence rates were 3.3%, 6.6%, and 15.0% at 5, 10, and 15 years, respectively. Among 804 patients followed more than 5 years, overall cumulative incidence rates of pancreatic carcinoma were 3.5% at 10 years and 12.0% at 15 years from the initial diagnosis. The size of the IPMN and the diameter of the main pancreatic duct associated with incidence of IPMN-derived carcinoma (SHR 1.85; 95% confidence interval 1.38-2.48 for a 10-mm increase in the IPMN size and SHR 1.56; 95% confidence interval 1.33-1.83 for a 1-mm increase in the main pancreatic duct diameter) but not with incidence of concomitant PDAC.

CONCLUSIONS

In a large long-term study of patients with branch-duct IPMNs, we found the 5-year incidence rate of pancreatic malignancy to be 3.3%, reaching 15.0% at 15 years after IPMN diagnosis. We observed heterogeneous risk factor profiles between IPMN-derived and concomitant carcinomas.

Management of patients with increased risk for familial pancreatic cancer: updated recommendations from the International Cancer of the Pancreas Screening (CAPS) Consortium

BACKGROUND AND AIM

The International Cancer of the Pancreas Screening Consortium met in 2018 to update its consensus recommendations for the management of individuals with increased risk of pancreatic cancer based on family history or germline mutation status (high-risk individuals).

METHODS

A modified Delphi approach was employed to reach consensus among a multidisciplinary group of experts who voted on consensus statements. Consensus was considered reached if ≥75% agreed or disagreed.

RESULTS

Consensus was reached on 55 statements. The main goals of surveillance (to identify high-grade dysplastic precursor lesions and T1N0M0 pancreatic cancer) remained unchanged. Experts agreed that for those with familial risk, surveillance should start no earlier than age 50 or 10 years earlier than the youngest relative with pancreatic cancer, but were split on whether to start at age 50 or 55. Germline ATM mutation carriers with one affected first-degree relative are now considered eligible for surveillance. Experts agreed that preferred surveillance tests are endoscopic ultrasound and MRI/magnetic retrograde cholangiopancreatography, but no consensus was reached on how to alternate these modalities. Annual surveillance is recommended in the absence of concerning lesions. Main areas of disagreement included if and how surveillance should be performed for hereditary pancreatitis, and the management of indeterminate lesions.

CONCLUSIONS

Pancreatic surveillance is recommended for selected high-risk individuals to detect early pancreatic cancer and its high-grade precursors, but should be performed in a research setting by multidisciplinary teams in centres with appropriate expertise. Until more evidence supporting these recommendations is available, the benefits, risks and costs of surveillance of pancreatic surveillance need additional evaluation.

Genetic analysis of postoperative recurrence of pancreatic cancer potentially owing to needle tract seeding during EUS-FNB

Background and study aims  Needle tract seeding during endoscopic ultrasound fine-needle biopsy (EUS-FNB) remains a concern. We investigated whether such seeding occurred in a patient with pancreatic ductal adenocarcinoma (PDA). Patient and methods  Surgically resected and EUS-FNB-derived specimens were genotyped to determine if a gastric wall tumor that emerged 3 years after curative resection of an early-stage PDA was clonally related to the original tumor. Results  The gastric tumor histologically resembled the primary PDA; the lesions also shared KRAS , SMAD4 , and RNF43 mutations. Genotyping of the preoperative EUS-FNB specimen, in which cancer was not detected, nevertheless revealed mutations that were identical to those in the resected primary and recurrent tumors. While the primary PDA had a low frequency of mutant SMAD4 , such mutations were highly prevalent in both the EUS-FNB and recurrent tumor specimens. Conclusions  The genetic lineages of sampled tissues from our patient revealed that needle tract seeding may have incidentally occurred when a subset of neoplastic cells within a heterogeneous tumor ( i. e. , an aggressive clone) was targeted during EUS-FNB.

Enrichment of oral microbiota in early cystic precursors to invasive pancreatic cancer

OBJECTIVES

Intraductal papillary mucinous neoplasms (IPMNs) are pancreatic cysts that can progress to invasive pancreatic cancer. Associations between oncogenesis and oral microbiome alterations have been reported. This study aims to investigate a potential intracystic pancreatic microbiome in a pancreatic cystic neoplasm (PCN) surgery patient cohort.

DESIGN

Paired cyst fluid and plasma were collected at pancreatic surgery from patients with suspected PCN (n=105). Quantitative and qualitative assessment of bacterial DNA by qPCR, PacBio sequencing (n=35), and interleukin (IL)-1β quantification was performed. The data were correlated to diagnosis, lesion severity and clinical and laboratory profile, including proton-pump inhibitor (PPI) usage and history of invasive endoscopy procedures.

RESULTS

Intracystic bacterial 16S DNA copy number and IL-1β protein quantity were significantly higher in IPMN with high-grade dysplasia and IPMN with cancer compared with non-IPMN PCNs. Despite high interpersonal variation of intracystic microbiota composition, bacterial network and linear discriminant analysis effect size analyses demonstrated co-occurrence and enrichment of oral bacterial taxa including Fusobacterium nucleatum and Granulicatella adiacens in cyst fluid from IPMN with high-grade dysplasia. The elevated intracystic bacterial DNA is associated with, but not limited to, prior exposure to invasive endoscopic procedures, and is independent from use of PPI and antibiotics.

CONCLUSIONS

Collectively, these findings warrant further investigation into the role of oral bacteria in cystic precursors to pancreatic cancer and have added values on the aetiopathology as well as the management of pancreatic cysts.

Intraductal papillary mucinous carcinoma versus pancreatic ductal adenocarcinoma: A systematic review and meta-analysis

BACKGROUND

Previous studies have indicated that there may be a difference in tumor biology between intraductal papillary mucinous carcinoma (IPMC) and pancreatic ductal adenocarcinoma (PDAC). However, the data are still controversial. The aim of this systematic review and meta-analysis was to summarize and compare the outcome of IPMC and PDAC after surgical resection.

METHODS

Studies comparing IPMC and PDAC were identified using Medline and Embase search engines. Primary outcomes of interest were survival and recurrence. Secondary outcomes were clinicopathological characteristics. Meta-analysis of data was conducted using a random-effects model.

RESULTS

A total of 14 studies were included. Pooled analysis revealed an improved 5-year overall survival (OS) for IPMC compared to PDAC (OR 0.23, 95% CI 0.09-0.56). Both colloid and tubular IPMC showed improved 5-year OS compared to PDAC (OR 0.12, 95% CI 0.05-0.25 and OR 0.38, 95% CI 0.26-0.54, respectively). Median survival time ranged from 21 to 58 months in the IPMC group compared to 12-23 months in the PDAC group. No meta-analysis could be performed on recurrence or on time-to-event data. Descriptive data showed no survival difference for higher TNM stages. IPMC was more often found at a TNM-stage of 1 (OR 4.40, 95% CI 2.71-7.15) and had lower rates of lymph node spread (OR 0.43, 95% CI 0.32-0.57).

CONCLUSION

Available data suggest that IPMC has a more indolent course with a better 5-year OS compared to PDAC. The histopathological features are less aggressive in IPMC. The reason may be earlier detection. However, for IPMC with higher TNM stages the survival seems to be similar to that of PDAC.

Diagnosis and management of pancreatic cystic neoplasms: current evidence and guidelines

Pancreatic cystic neoplasms (PCN) are a heterogeneous group of pancreatic cysts that include intraductal papillary mucinous neoplasms, mucinous cystic neoplasms, serous cystic neoplasms and other rare cystic lesions, all with different biological behaviours and variable risk of progression to malignancy. As more pancreatic cysts are incidentally discovered on routine cross-sectional imaging, optimal surveillance for patients with PCN is becoming an increasingly common clinical problem, highlighting the need to balance cancer prevention with the risk of (surgical) overtreatment. This Review summarizes the latest developments in the diagnosis and management of PCN, including the quality of available evidence. Also discussed are the most important differences between the PCN guidelines from the American Gastroenterological Association, the International Association of Pancreatology and the European Study Group on Cystic Tumours of the Pancreas, including diagnostic and follow-up strategies and indications for surgery. Finally, new developments in the management of patients with PCN are addressed.

From somatic mutation to early detection: insights from molecular characterization of pancreatic cancer precursor lesions

Pancreatic cancer arises from noninvasive precursor lesions, including pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN), which are curable if detected early enough. Recently, these types of precursor lesions have been extensively characterized at the molecular level, defining the timing of critical genetic alterations in tumorigenesis pathways. The results of these studies deepen our understanding of tumorigenesis in the pancreas, providing novel insights into tumor initiation and progression. Perhaps more importantly, they also provide a rational foundation for early detection approaches that could allow clinical intervention prior to malignant transformation. In this review, we summarize the results of comprehensive molecular characterization of PanINs, IPMNs, and MCNs and discuss the implications for cancer biology as well as early detection. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Intraductal Papillary Mucinous Neoplasms Arise From Multiple Independent Clones, Each With Distinct Mutations

BACKGROUND & AIMS

Intraductal papillary mucinous neoplasms (IPMNs) are lesions that can progress to invasive pancreatic cancer and constitute an important system for studies of pancreatic tumorigenesis. We performed comprehensive genomic analyses of entire IPMNs to determine the diversity of somatic mutations in genes that promote tumorigenesis.

METHODS

We microdissected neoplastic tissues from 6-24 regions each of 20 resected IPMNs, resulting in 227 neoplastic samples that were analyzed by capture-based targeted sequencing. Somatic mutations in genes associated with pancreatic tumorigenesis were assessed across entire IPMN lesions, and the resulting data were supported by evolutionary modeling, whole-exome sequencing, and in situ detection of mutations.

RESULTS

We found a high prevalence of heterogeneity among mutations in IPMNs. Heterogeneity in mutations in KRAS and GNAS was significantly more prevalent in IPMNs with low-grade dysplasia than in IPMNs with high-grade dysplasia (P < .02). Whole-exome sequencing confirmed that IPMNs contained multiple independent clones, each with distinct mutations, as originally indicated by targeted sequencing and evolutionary modeling. We also found evidence for convergent evolution of mutations in RNF43 and TP53, which are acquired during later stages of tumorigenesis.

CONCLUSIONS

In an analysis of the heterogeneity of mutations throughout IPMNs, we found that early-stage IPMNs contain multiple independent clones, each with distinct mutations, indicating their polyclonal origin. These findings challenge the model in which pancreatic neoplasms arise from a single clone. Increasing our understanding of the mechanisms of IPMN polyclonality could lead to strategies to identify patients at increased risk for pancreatic cancer.

Role of endoscopic ultrasound in the screening and follow-up of high-risk individuals for familial pancreatic cancer

Managing familial pancreatic cancer (FPC) is challenging for gastroenterologists, surgeons and oncologists. High-risk individuals (HRI) for pancreatic cancer (PC) (FPC or with germline mutations) are a heterogeneous group of subjects with a theoretical lifetime cumulative risk of PC over 5%. Screening is mainly based on annual magnetic resonance imaging (MRI) and endoscopic ultrasound (EUS). The goal of screening is to identify early-stage operable cancers or high-risk precancerous lesions (pancreatic intraepithelial neoplasia or intraductal papillary mucinous neoplasms with high-grade dysplasia). In the literature, target lesions are identified in 2%-5% of HRI who undergo screening. EUS appears to provide better identification of small solid lesions (0%-46% of HRI) and chronic-pancreatitis-like parenchymal changes (14%-77% of HRI), while MRI is probably the best modality to identify small cystic lesions (13%-49% of HRI). There are no specific studies in HRI on the use of contrast-enhanced harmonic EUS. EUS can also be used to obtain tissue samples. Nevertheless, there is still limited evidence on the accuracy of imaging procedures used for screening or agreement on which patients to treat. The cost-effectiveness of screening is also unclear. Certain new EUS-related techniques, such as searching for DNA abnormalities or protein markers in pancreatic fluid, appear to be promising.

Mutational Patterns in Pancreatic Juice of Intraductal Papillary Mucinous Neoplasms and Concomitant Pancreatic Cancer

OBJECTIVES

The aims of this study were to identify genetic characteristics of intraductal papillary mucinous neoplasm (IPMN)-associated pancreatic ductal carcinoma (PDC) and to detect these markers using pancreatic juice.

METHODS

From 76 cases, 102 tissues were obtained: 29 cases were noninvasive IPMN, 18 were PDC derived from IPMN (D-PDC; noninvasive part, n = 16; invasive part, n = 18), and 29 were PDC concomitant with IPMN (C-PDC; IPMN part, n = 10; PDC part, n = 29). Moreover, pancreatic juice samples from 28 cases were obtained (noninvasive IPMN, n = 13; D-PDC, n = 7; C-PDC, n = 8). Fifty-one cancer-related genes were analyzed by next-generation sequencing.

RESULTS

TP53 mutation rates in D-PDC, C-PDC, and noninvasive IPMN were 67%, 66%, and 10%, respectively. Moreover, KRAS mutational patterns between 2 simultaneous tumors differed in 1 (6.3%) of the 16 D-PDC cases and in 8 (80%) of the 10 C-PDC cases (P = 0.0006). TP53 or multiple KRAS mutations were detected using pancreatic juice more frequently in C-PDC cases than in noninvasive IPMN cases (75% and 23%, respectively, P = 0.03).

CONCLUSIONS

Multiple KRAS mutations along with TP53 mutation are genetic markers for C-PDC, which could be detected using pancreatic juice preoperatively.

Human pancreatic cancer cell exosomes, but not human normal cell exosomes, act as an initiator in cell transformation

Cancer evolves through a multistep process that occurs by the temporal accumulation of genetic mutations. Tumor-derived exosomes are emerging contributors to tumorigenesis. To understand how exosomes might contribute to cell transformation, we utilized the classic two-step NIH/3T3 cell transformation assay and observed that exosomes isolated from pancreatic cancer cells, but not normal human cells, can initiate malignant cell transformation and these transformed cells formed tumors in vivo. However, cancer cell exosomes are unable to transform cells alone or to act as a promoter of cell transformation. Utilizing proteomics and exome sequencing, we discovered cancer cell exosomes act as an initiator by inducing random mutations in recipient cells. Cells from the pool of randomly mutated cells are driven to transformation by a classic promoter resulting in foci, each of which encode a unique genetic profile. Our studies describe a novel molecular understanding of how cancer cell exosomes contribute to cell transformation.

Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that major issues remain unresolved (see decision letter).

Pancreatic cancer arising in the remnant pancreas is not always a relapse of the preceding primary

This study aimed to understand the biology of pancreatic ductal adenocarcinoma that arises in the remnant pancreas after surgical resection of a primary pancreatic ductal adenocarcinoma, using integrated histological and molecular analysis. Patients who underwent a completion pancreatectomy for local recurrence following resection of a primary pancreatic ductal adenocarcinoma were studied with histological analysis and next-generation sequencing of the primary and the recurrent cancer. Of six patients that met the inclusion criteria, three cases were classified as "true" recurrences, i.e., the primary and the cancer in the remnant pancreas shared both morphological features and molecular alterations. Two cases were identified as having independent cancers that exhibited different histological and molecular profiles. In the remaining case, the relationship could not be determined. Pancreatic ductal adenocarcinoma that arises in the remnant pancreas can be either a second primary or a "true" relapse of the preceding primary. The differentiation of second primaries from local recurrences may have important implications for patient management.

Genetics of Familial and Sporadic Pancreatic Cancer

In the previous decade, comprehensive genomic analyses have yielded important insights about the genetic alterations that underlie pancreatic tumorigenesis. Whole-exome and whole-genome sequencing of pancreatic ductal adenocarcinomas have confirmed the critical driver genes altered in the majority of pancreatic cancers, as well as identified numerous less frequently altered driver genes, and have delineated cancer subgroups with unique biological and clinical features. It is now appreciated that pancreatic susceptibility gene alterations are often identified in patients with pancreatic cancer without family histories suggestive of a familial cancer syndrome, prompting recent efforts to expand gene testing to all patients with pancreatic cancer. Studies of pancreatic cancer precursor lesions have begun to elucidate the evolutionary history of pancreatic tumorigenesis and to help us understand the utility of biomarkers for early detection and targets to develop new therapeutic strategies. In this review, we discuss the results of comprehensive genomic characterization of pancreatic ductal adenocarcinoma and its precursor lesions, and we highlight translational applications in early detection and therapy.

Clinical assessment of the GNAS mutation status in patients with intraductal papillary mucinous neoplasm of the pancreas

Intraductal papillary mucinous neoplasm (IPMN) of the pancreas is characterized by cystic dilation of the pancreatic duct, caused by mucin hypersecretion, with slow progression via the adenoma-carcinoma sequence mechanism. Mutation of GNAS at codon 201 is found exclusively in IPMNs, occurring at a rate of 41-75%. Recent advances in molecular biological techniques have demonstrated that GNAS mutation might play a role in the transformation of IPMNs after the appearance of neoplastic cells, rather than in the tumorigenesis of IPMNs. GNAS mutation is observed frequently in the intestinal subtype of IPMNs with MUC2 expression, and less frequently in IPMNs with concomitant pancreatic ductal adenocarcinoma (PDAC). Research has focused on assessing GNAS mutation status in clinical practice using various samples. In this review, we discuss the clinical application of GNAS mutation assessment to differentiate invasive IPMNs from concomitant PDAC, examine the clonality of recurrent IPMNs in the remnant pancreas using resected specimens, and differentiate pancreatic cystic lesions using cystic fluid collected by endoscopic ultrasound-guided fine needle aspiration (EUS-FNA), duodenal fluid, and serum liquid biopsy samples.

Clinicopathological characterization of SMAD4-mutated intestinal adenocarcinomas: A case-control study

The SMAD4 tumor suppressor gene product inhibits transforming growth factor-β-mediated signaling and is mutated in ~10% of colorectal carcinomas. The prognostic significance of SMAD4 mutations has been controversial. We studied the pathological and clinical characteristics of SMAD4-mutated intestinal adenocarcinomas using a retrospective case-control study design. Cases and controls were identified among 443 primary adenocarcinomas that had undergone next generation DNA sequencing (NGS) with the Ion AmpliSeq Cancer Hotspot Panel v2, which evaluates 50 cancer-related genes. Twenty-eight SMAD4-mutated (SMAD4m) patients were matched 1:2 with 56 consecutive SMAD4 wild-type (SMAD4wt) control patients from the same analysis stream. Compared with the SMAD4wt controls, the SMAD4m tumors were of higher stage (P = 0.026) and were more likely to feature mucinous differentiation (P = 0.0000), to occur in the setting of Crohn’s disease (P = 0.0041), and to harbor concurrent RAS mutations (P = 0.0178). Tumor mucin content was significantly correlated with mutations involving the MH2 domain of the SMAD4 protein (P = 0.0338). Correspondence between mutation sites and morphology was demonstrated directly in a mixed adenocarcinoma and neuroendocrine tumor where SMAD4 mutations involving different protein domains were found in histologically disparate tumor regions despite both containing identical KRAS and TP53 mutations.

Pathways of Progression From Intraductal Papillary Mucinous Neoplasm to Pancreatic Ductal Adenocarcinoma Based on Molecular Features

BACKGROUND & AIMS

Intraductal papillary mucinous neoplasms (IPMNs) are regarded as precursors of pancreatic ductal adenocarcinomas (PDAs), but little is known about the mechanism of progression. This makes it challenging to assess cancer risk in patients with IPMNs. We investigated associations of IPMNs with concurrent PDAs by genetic and histologic analyses.

METHODS

We obtained 30 pancreatic tissues with concurrent PDAs and IPMNs, and 168 lesions, including incipient foci, were mapped, microdissected, and analyzed for mutations in 18 pancreatic cancer-associated genes and expression of tumor suppressors.

RESULTS

We determined the clonal relatedness of lesions, based on driver mutations shared by PDAs and concurrent IPMNs, and classified the lesions into 3 subtypes. Twelve PDAs contained driver mutations shared by all concurrent IPMNs, which we called the sequential subtype. This subset was characterized by less diversity in incipient foci with frequent GNAS mutations. Eleven PDAs contained some driver mutations that were shared with concurrent IPMNs, which we called the branch-off subtype. In this subtype, PDAs and IPMNs had identical KRAS mutations but different GNAS mutations, although the lesions were adjacent. Whole-exome sequencing and methylation analysis of these lesions indicated clonal origin with later divergence. Ten PDAs had driver mutations not found in concurrent IPMNs, called the de novo subtype. Expression profiles of TP53 and SMAD4 increased our ability to differentiate these subtypes compared with sequencing data alone. The branch-off and de novo subtypes had substantial heterogeneity among early clones, such as differences in KRAS mutations. Patients with PDAs of the branch-off subtype had a longer times of disease-free survival than patients with PDAs of the de novo or the sequential subtypes.

CONCLUSIONS

Detailed histologic and genetic analysis of PDAs and concurrent IPMNs identified 3 different pathways by which IPMNs progress to PDAs-we call these the sequential, branch-off, and de novo subtypes. Subtypes might be associated with clinical and pathologic features and be used to select surveillance programs for patients with IPMNs.

Histo-molecular oncogenesis of pancreatic cancer: From precancerous lesions to invasive ductal adenocarcinoma

Pancreatic cancer is a lethal malignancy, whose precursor lesions are pancreatic intraepithelial neoplasm, intraductal papillary mucinous neoplasm, intraductal tubulopapillary neoplasm, and mucinous cystic neoplasm. To better understand the biology of pancreatic cancer, it is fundamental to know its precursors and to study the mechanisms of carcinogenesis. Each of these precursors displays peculiar histological features, as well as specific molecular alterations. Starting from such pre-invasive lesions, this review aims at summarizing the most important aspects of carcinogenesis of pancreatic cancer, with a specific focus on the recent advances and the future perspectives of the research on this lethal tumor type.

Pancreatic Cystic Lesions: Pathogenesis and Malignant Potential

Pancreatic cancer remains one of the most lethal cancers despite extensive research. Further understanding of precursor lesions may enhance the ability to treat and prevent pancreatic cancer. Pancreatic cystic lesions (PCLs) with malignant potential include: mucinous PCLs (intraductal papillary mucinous neoplasms and mucinous cystic neoplasm), solid pseudopapillary tumors and cystic neuroendocrine tumors. This review summarizes the latest literature describing what is known about the pathogenesis and malignant potential of these PCLs, including unique epidemiological, radiological, histological, genetic and molecular characteristics.