Imaging features of intraductal papillary mucinous neoplasms of the pancreas in multi-detector row computed tomography

Pancreatic intraductal papillary mucinous neoplasms: Current diagnosis and management

Intraductal papillary mucinous neoplasms (IPMNs) represent approximately 1% of all pancreatic neoplasms and 25% of cystic neoplasms. They are divided into three types: main duct-IPMN (MD-IPPMN), branch duct-IPMN (BD-IPMN), and mixed type-IPMN. In this review, diagnostics, including clinical presentation and radiological investigations, were described. Magnetic resonance imaging is the most useful for most IPMNs. Management depends on the type and radiological features of IPMNs. Surgery is recommended for MD-IPMN. For BD-IPMN, management involves surgery or surveillance depending on the tumor size, cyst growth rate, solid components, main duct dilatation, high-grade dysplasia in cytology, the presence of symptoms (jaundice, new-onset diabetes, pancreatitis), and CA 19.9 serum level. The patient’s age and comorbidities should also be taken into consideration. Currently, there are different guidelines regarding the diagnosis and management of IPMNs. In this review, the following guidelines were presented: Sendai International Association of Pancreatology guidelines (2006), American Gastroenterological Association guidelines, revised international consensus Fukuoka guidelines (2012), revised international consensus Fukuoka guidelines (2017), and European evidence-based guidelines according to the European Study Group on Cystic Tumours of the Pancreas (2018). The Verona Evidence-Based Meeting 2020 was also presented and discussed.

Imaging Features for Predicting High-Grade Dysplasia or Malignancy in Branch Duct Type Intraductal Papillary Mucinous Neoplasm of the Pancreas: A Systematic Review and Meta-Analysis

BACKGROUND

The consensus guidelines for branch-duct intraductal papillary mucinous neoplasm (BD-IPMN) of the pancreas are mostly based on imaging features. This study aimed to determine imaging features and their diagnostic accuracy for predicting high-grade dysplasia (HGD)/malignancy in BD-IPMN, including mixed type.

METHODS

The PubMed, Embase, and Cochrane databases were searched, and data were extracted from relevant studies. As the main diagnostic accuracy index, diagnostic odds ratios (DORs) of imaging features for diagnosing HGD/malignancy in BD-IPMNs were pooled using the random-effects model. A bivariate random-effects approach was used to construct summary receiver operating characteristic curves for sensitivity and specificity estimation.

RESULTS

The pooled DOR was the highest for the enhanced solid component/mural nodule (MN) (DOR, 12.21; 95 % confidence interval [CI], 6.14-24.27), followed by a main pancreatic duct (MPD) diameter of 10 mm or greater (DOR, 7.93; 95 % CI, 3.02-20.83), solid component (DOR, 4.85; 95 % CI, 2.49-9.42), lymphadenopathy (DOR, 4.84; 95 % CI, 1.11-21.06), MN (DOR, 4.48; 95 % CI, 3.15-6.39), an MPD diameter of 5 mm or greater (DOR, 3.69; 95 % CI, 2.62-5.19), abrupt change in MPD caliber with distal pancreatic atrophy (DOR, 2.65; 95 % CI, 1.66-4.24), thickened/enhancing walls (DOR, 2.38; 95 % CI, 1.57-3.60), and cyst size of 3 cm or larger (DOR, 1.98; 95 % CI, 1.48-2.64). The largest area under the curve (0.89 and 0.95, respectively) and high specificity (0.95 and 0.98, respectively) also were found for enhanced solid component/MN and an MPD diameter of 10 mm or greater, albeit with low sensitivity (0.38 and 0.14, respectively).

CONCLUSIONS

The aforementioned imaging features could aid in predicting HGD/malignancy of BD-IPMN. Furthermore, enhanced solid component/MN and an MPD diameter of 10 mm or greater were the most important predictors of HGD/malignancy in BD-IPMN and should be considered as indications for surgery.

Systematic review, meta-analysis, and a high-volume center experience supporting the new role of mural nodules proposed by the updated 2017 international guidelines on IPMN of the pancreas

BACKGROUND

Mural nodules (MNs) have a predominant role in the 2016 revision of the international guidelines on intraductal papillary mucinous neoplasms (IPMN) of the pancreas. The aim of this study was to evaluate MNs as predictors of invasive cancer (iCa) or high-grade dysplasia (HGD) in IPMNs and to investigate the role of MN size in risk prediction.

METHODS

A PRISMA-compliant systematic review of the literature and meta-analysis on selected studies were conducted. The random effect model was adopted, and the pooled SMD (standardized mean difference) obtained. The surgical series of IPMNs at a single high-volume institution was reviewed.

RESULTS

This review included 70 studies and 2297 resected IPMNs. MNs have a positive predictive value for malignancy of 62.2%. The meta-analysis suggested that MN size has a considerable effect on predicting IPMNs with both iCa or HGD with a mean SMD of 0.79. All studies included in the meta-analysis used contrast-enhanced endosonography (CE-EUS) to assess MNs. Due to the heterogeneity of the proposed thresholds, no reliable MN size cut-off was identified. Of 317 IPMNs resected at our institution, 102 (32.1%) had a preoperative diagnosis of MN. Multivariate analysis showed that MN is the only independent predictor of iCa and HGD for all types of IPMNs.

CONCLUSION

MNs are reliable predictors of iCa and HGD in IPMNs as proposed by the 2016 IAP guidelines. CE-EUS seems to be the best tool for characterizing size and has the best accuracy for predicting malignancy. Further studies should determine potential MN dimensional cut-offs.

Imaging modalities for characterising focal pancreatic lesions

BACKGROUND

Increasing numbers of incidental pancreatic lesions are being detected each year. Accurate characterisation of pancreatic lesions into benign, precancerous, and cancer masses is crucial in deciding whether to use treatment or surveillance. Distinguishing benign lesions from precancerous and cancerous lesions can prevent patients from undergoing unnecessary major surgery. Despite the importance of accurately classifying pancreatic lesions, there is no clear algorithm for management of focal pancreatic lesions.

OBJECTIVES

To determine and compare the diagnostic accuracy of various imaging modalities in detecting cancerous and precancerous lesions in people with focal pancreatic lesions.

SEARCH METHODS

We searched the CENTRAL, MEDLINE, Embase, and Science Citation Index until 19 July 2016. We searched the references of included studies to identify further studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We planned to include studies reporting cross-sectional information on the index test (CT (computed tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), EUS (endoscopic ultrasound), EUS elastography, and EUS-guided biopsy or FNA (fine-needle aspiration)) and reference standard (confirmation of the nature of the lesion was obtained by histopathological examination of the entire lesion by surgical excision, or histopathological examination for confirmation of precancer or cancer by biopsy and clinical follow-up of at least six months in people with negative index tests) in people with pancreatic lesions irrespective of language or publication status or whether the data were collected prospectively or retrospectively.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched the references to identify relevant studies and extracted the data. We planned to use the bivariate analysis to calculate the summary sensitivity and specificity with their 95% confidence intervals and the hierarchical summary receiver operating characteristic (HSROC) to compare the tests and assess heterogeneity, but used simpler models (such as univariate random-effects model and univariate fixed-effect model) for combining studies when appropriate because of the sparse data. We were unable to compare the diagnostic performance of the tests using formal statistical methods because of sparse data.

MAIN RESULTS

We included 54 studies involving a total of 3,196 participants evaluating the diagnostic accuracy of various index tests. In these 54 studies, eight different target conditions were identified with different final diagnoses constituting benign, precancerous, and cancerous lesions. None of the studies was of high methodological quality. None of the comparisons in which single studies were included was of sufficiently high methodological quality to warrant highlighting of the results. For differentiation of cancerous lesions from benign or precancerous lesions, we identified only one study per index test. The second analysis, of studies differentiating cancerous versus benign lesions, provided three tests in which meta-analysis could be performed. The sensitivities and specificities for diagnosing cancer were: EUS-FNA: sensitivity 0.79 (95% confidence interval (CI) 0.07 to 1.00), specificity 1.00 (95% CI 0.91 to 1.00); EUS: sensitivity 0.95 (95% CI 0.84 to 0.99), specificity 0.53 (95% CI 0.31 to 0.74); PET: sensitivity 0.92 (95% CI 0.80 to 0.97), specificity 0.65 (95% CI 0.39 to 0.84). The third analysis, of studies differentiating precancerous or cancerous lesions from benign lesions, only provided one test (EUS-FNA) in which meta-analysis was performed. EUS-FNA had moderate sensitivity for diagnosing precancerous or cancerous lesions (sensitivity 0.73 (95% CI 0.01 to 1.00) and high specificity 0.94 (95% CI 0.15 to 1.00), the extremely wide confidence intervals reflecting the heterogeneity between the studies). The fourth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (dysplasia) provided three tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing invasive carcinoma were: CT: sensitivity 0.72 (95% CI 0.50 to 0.87), specificity 0.92 (95% CI 0.81 to 0.97); EUS: sensitivity 0.78 (95% CI 0.44 to 0.94), specificity 0.91 (95% CI 0.61 to 0.98); EUS-FNA: sensitivity 0.66 (95% CI 0.03 to 0.99), specificity 0.92 (95% CI 0.73 to 0.98). The fifth analysis, of studies differentiating cancerous (high-grade dysplasia or invasive carcinoma) versus precancerous (low- or intermediate-grade dysplasia) provided six tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing cancer (high-grade dysplasia or invasive carcinoma) were: CT: sensitivity 0.87 (95% CI 0.00 to 1.00), specificity 0.96 (95% CI 0.00 to 1.00); EUS: sensitivity 0.86 (95% CI 0.74 to 0.92), specificity 0.91 (95% CI 0.83 to 0.96); EUS-FNA: sensitivity 0.47 (95% CI 0.24 to 0.70), specificity 0.91 (95% CI 0.32 to 1.00); EUS-FNA carcinoembryonic antigen 200 ng/mL: sensitivity 0.58 (95% CI 0.28 to 0.83), specificity 0.51 (95% CI 0.19 to 0.81); MRI: sensitivity 0.69 (95% CI 0.44 to 0.86), specificity 0.93 (95% CI 0.43 to 1.00); PET: sensitivity 0.90 (95% CI 0.79 to 0.96), specificity 0.94 (95% CI 0.81 to 0.99). The sixth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (low-grade dysplasia) provided no tests in which meta-analysis was performed. The seventh analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) provided two tests in which meta-analysis was performed. The sensitivity and specificity for diagnosing cancer were: CT: sensitivity 0.83 (95% CI 0.68 to 0.92), specificity 0.83 (95% CI 0.64 to 0.93) and MRI: sensitivity 0.80 (95% CI 0.58 to 0.92), specificity 0.81 (95% CI 0.53 to 0.95), respectively. The eighth analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) or benign lesions provided no test in which meta-analysis was performed.There were no major alterations in the subgroup analysis of cystic pancreatic focal lesions (42 studies; 2086 participants). None of the included studies evaluated EUS elastography or sequential testing.

AUTHORS' CONCLUSIONS

We were unable to arrive at any firm conclusions because of the differences in the way that study authors classified focal pancreatic lesions into cancerous, precancerous, and benign lesions; the inclusion of few studies with wide confidence intervals for each comparison; poor methodological quality in the studies; and heterogeneity in the estimates within comparisons.

Serum Carbohydrate Antigen 19-9 in Differential Diagnosis of Benign and Malignant Pancreatic Cystic Neoplasms: A Meta-Analysis

Background

Using serum carbohydrate antigen 19–9 (CA 19–9) in discriminating between benign and malignant pancreatic disease remains controversial. We aim to evaluate the diagnostic value of serum CA 19–9 in predicting malignant pancreatic cystic lesions.

Methods

Eligible studies were identified through searching MEDLINE and EMBASE prior to March 2016. Studies were assessed for quality using the Quality Assessment for Studies of Diagnostic Accuracy, 2nd version (QUADAS-2). Pooled sensitivity and specificity with 95% confidence interval (CI) were calculated using random-effects models. Summary receiver operator characteristic (SROC) curves and the area under curve (AUC) were performed.

Results

A total of thirteen studies including 1437 patients were enrolled in this meta-analysis. The pooled sensitivity and specificity were 0.47(95% CI: 0.35–0.59), and 0.88(95% CI: 0.86–0.91), respectively, and the AUC was 0.87(95% CI, 0.84–0.90). Meta-regression analysis showed that sample size, region and reference standards were not the main sources of heterogeneity.

Conclusions

Serum CA 19–9 has satisfying pooled specificity while poor pooled sensitivity for discriminating benign from malignant PCNs. It deserves to be widely used as complementary to other clinical diagnostic methods.

What Is the Best Way to Identify Malignant Transformation Within Pancreatic IPMN: A Systematic Review and Meta-Analyses

OBJECTIVES

Pancreatic intraductal papillary mucinous neoplasias (IPMNs) represent 25% of all cystic neoplasms and are precursor lesions for pancreatic ductal adenocarcinoma. This study aims to identify the best imaging modality for detecting malignant transformation in IPMN, the sensitivity and specificity of risk features on imaging, and the usefulness of tumor markers in serum and cyst fluid to predict malignancy in IPMN.

METHODS

Databases were searched from November 2006 to March 2014. Pooled sensitivity and specificity of diagnostic techniques/imaging features of suspected malignancy in IPMN using a hierarchical summary receiver operator characteristic (HSROC) approach were performed.

RESULTS

A total of 467 eligible studies were identified, of which 51 studies met the inclusion criteria and 37 of these were incorporated into meta-analyses. The pooled sensitivity and specificity for risk features predictive of malignancy on computed tomography/magnetic resonance imaging were 0.809 and 0.762 respectively, and on positron emission tomography were 0.968 and 0.911. Mural nodule, cyst size, and main pancreatic duct dilation found on imaging had pooled sensitivity for prediction of malignancy of 0.690, 0.682, and 0.614, respectively, and specificity of 0.798, 0.574, and 0.687. Raised serum carbohydrate antigen 19-9 (CA19-9) levels yielded sensitivity of 0.380 and specificity of 0903. Combining parameters yielded a sensitivity of 0.743 and specificity of 0.906.

CONCLUSIONS

PET holds the most promise in identifying malignant transformation within an IPMN. Combining parameters increases sensitivity and specificity; the presence of mural nodule on imaging was the most sensitive whereas raised serum CA19-9 (>37 KU/l) was the most specific feature predictive of malignancy in IPMNs.

CT of the pancreas: comparison of image quality and pancreatic duct depiction among model-based iterative, adaptive statistical iterative, and filtered back projection reconstruction techniques

The purpose of this study is to compare CT images of the pancreas reconstructed with model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASiR), and filtered back projection (FBP) techniques for image quality and pancreatic duct (PD) depiction. Data from 40 patients with contrast-enhanced abdominal CT [CTDIvol: 10.3 ± 3.0 (mGy)] during the late arterial phase were reconstructed with FBP, 40% ASiR-FBP blending, and MBIR. Two radiologists assessed the depiction of the main PD, image noise, and overall image quality using 5-point scale independently. Objective CT value and noise were measured in the pancreatic parenchyma, and the contrast-to-noise ratio (CNR) of the PD was calculated. The Friedman test and post-hoc multiple comparisons with Bonferroni test following one-way ANOVA were used for qualitative and quantitative assessment, respectively. For the subjective assessment, scores for MBIR were significantly higher than those for FBP and 40% ASiR (all P < 0.001). No significant differences in CT values of the pancreatic parenchyma were noted among FBP, 40% ASiR, and MBIR images (P > 0.05). Objective image noise was significantly lower and CNR of the PD was higher with MBIR than with FBP and 40% ASiR (all P < 0.05). Our results suggest that pancreatic CT images reconstructed with MBIR have lower image noise, better image quality, and higher conspicuity and CNR of the PD compared with FBP and ASiR.

Is it safe to follow side branch IPMNs?

Management of Bd-IPMN remains challenging. Critical appraisal of the published literature reveals that the actual treatment of what is presumed to be Bd-IPMN remains unsatisfactory, with a high rate of surgically overtreated patients. Until we accrue more precise knowledge of the natural history of Bd-IPMN, management of patients with this presumed diagnosis should be individually tailored and preferably carried out in centers with a high expertise. For now, the authors strongly think that the old guidelines should be followed in most patients because these have proven to correctly identify lesions that can be safely followed. Although the new guidelines allow for follow-up of lesions greater than 3 cm, and for the most part this is safe, they should be used cautiously in younger patients because very close surveillance would be required for their long remaining lifespan.

Imaging features to distinguish malignant and benign branch-duct type intraductal papillary mucinous neoplasms of the pancreas: a meta-analysis

OBJECTIVE

To systematically determine the imaging findings for distinguishing malignant and benign branch-duct type intraductal papillary mucinous neoplasms (BD-IPMNs), including mixed type, and their diagnostic value through meta-analysis of published studies.

BACKGROUND

Management of BD-IPMNs, including mixed type, largely relies on imaging findings. The current knowledge on imaging findings to distinguish malignant and benign BD-IPMNs has weak evidence and is mostly from scattered individual retrospective studies.

METHODS

Thorough literature search in Ovid-MEDLINE and EMBASE databases was conducted to identify studies where findings of computed tomography, magnetic resonance imaging, and endoscopic ultrasonography of BD-IPMNs with or without main pancreatic duct (MPD) dilatation were correlated with surgical/pathological findings. Review of 1128 article candidates, including full-text review of 102 articles, identified 23 eligible articles with a total of 1373 patients for meta-analysis. Dichotomous data regarding distinction between malignant and benign BD-IPMNs were pooled using random effects model to obtain the diagnostic odds ratios (DORs) and their 95% confidence intervals (CIs) of various individual imaging findings for diagnosing malignant BD-IPMN.

RESULTS

Presence of mural nodules revealed the highest pooled DOR (95% CI) of 6.0 (4.1-8.8) followed by MPD dilatation [3.4 (2.3-5.2)], thick septum/wall [unadjusted, 3.3 (1.5-6.9); publication bias-adjusted, 2.3 (0.9-5.5)], and cyst size greater than 3 cm [2.3 (1.5-3.5)]. Multilocularity and multiplicity of the cystic lesions did not reveal statistically significant association with malignancy.

CONCLUSIONS

Presence of mural nodules should be regarded highly suspicious for malignancy warranting a surgical excision whereas cyst size greater than 3 cm, MPD dilatation (5-9 mm), or thick septum/wall may better be managed by careful observation and/or further evaluation.

Cyst features and risk of malignancy in intraductal papillary mucinous neoplasms of the pancreas: a meta-analysis

BACKGROUND & AIMS

International guidelines for the management of intraductal papillary mucinous neoplasms (IPMNs) of the pancreas recommend surgical resection of those with specific characteristics. We performed a meta-analysis to evaluate the risk of malignancy associated with each of these features of IPMNs.

METHODS

We performed a comprehensive search of MEDLINE from January 1, 1996, to November 11, 2011, for studies that included any of the features mentioned in the consensus guidelines for surgical resection of main duct and branch duct IPMNs. Data were analyzed from 41 studies for the following features: cyst size greater than 3 cm, the presence of mural nodules, dilated main pancreatic duct, symptoms, and main duct vs branch duct IPMNs. Malignant IPMNs were defined as those with carcinoma in situ or more advanced histology. A separate meta-analysis was performed for each risk factor to calculate pooled odds ratios (ORs). A random-effects model was used, based on the assumption of variation among study populations.

RESULTS

The risks of malignancy associated with individual cyst features were as follows: cyst size greater than 3 cm (OR, 62.4; 95% confidence interval [CI], 30.8-126.3), presence of a mural nodule (OR, 9.3; 95% CI, 5.3-16.1), dilatation of the main pancreatic duct (OR, 7.27; 95% CI, 3.0-17.4), and main vs branch duct IPMN (OR, 4.7; 95% CI, 3.3-6.9). There was a moderate level of heterogeneity among studies (I(2) range, 34-67).

CONCLUSIONS

Based on a meta-analysis, cyst features proposed by the international guidelines for resection of IPMN were highly associated with malignancy. However, based on our findings, not all cyst features should be weighted equally when considering risk of malignancy; cyst size greater than 3 cm was associated most strongly with malignant IPMN.

Progress in research of intraductal papillary mucinous neoplasms

Intraductal papillary mucinous neoplasms (IPMNs) represent a spectrum of neoplasms arising from the main pancreatic duct or branch ducts and producing mucin and can be regarded as a type of precancerous lesions. Thanks to improvements in endoscopy and imaging techniques, IPMNs are being diagnosed with increasing frequency. However, there are currently no highly sensitive and specific preoperative criteria available to distinguish benign IPMNs from malignant ones. What's more, the necessity for EUS and ERCP in the diagnosis of IPMNs is still under debate. Here, we review recent advances in research of IPMNs and summarize potential differences between benign and malignant IPMNs.

Imaging considerations in intraductal papillary mucinous neoplasms of the pancreas

With the widespread use of cross-sectional imaging, particularly computed tomography (CT) and magnetic resonance imaging (MRI), and the continuous improvement in the image quality of these techniques, the diagnosis of incidental pancreatic cysts has increased dramatically in the last decades. While the vast majority of these cysts are not clinically relevant, a small percentage of them will evolve into an invasive malignant tumor making their management challenging. Mucinous cystic neoplasms and intraductal papillary mucinous neoplasms (IPMN) are the most common pancreatic cystic lesions with malignant potential. Imaging findings on CT and MRI correlate tightly with the presence of malignant degeneration in these neoplasms. IPMN can be classified based on their distribution as main duct, branch duct or mixed type lesions. MRI is superior to CT in demonstrating the communication of a branch duct IPMN with the main pancreatic duct (MPD). Most branch duct lesions are benign whereas tumors involving the MPD are frequently associated with malignancy. The presence of solid nodules, thick enhancing walls and/or septae, a wide (> 1 cm) connection of a side-branch lesion with the MPD and the size of the tumor > 3 cm are indicative of malignancy in a branch and mixed type IPMN. A main pancreatic duct > 6 mm, a mural nodule > 3 mm and an abnormal attenuating area in the adjacent pancreatic parenchyma on CT correlates with malignant disease in main duct and mixed type IPMN. An accurate characterization of these neoplasms by imaging is thus crucial for selecting the best management options. In this article, we review the imaging findings of IPMN including imaging predictors of malignancy and surgical resectability. We also discuss follow-up strategies for patients with surgically resected IPMN and patients with incidental pancreatic cysts.