Magnetic resonance imaging of cystic pancreatic lesions in adults: an update in current diagnostic features and management

Conditions at risk of pancreatic cancer: The radiology perspective

Pancreatic cancer remains one for the most aggressive cancer worldwide, with pancreatic ductal adenocarcinoma being the most common malignant pancreatic lesion, associated with poor prognosis. While surgical resection is the only curative treatment, only a minority of patients is eligible for surgery due to its diagnosis at advanced stages. Therefore, strategies for early detection of pancreatic cancer are needed. This article aims to provide a state-of-the-art review of the most common conditions associated to an increased risk of pancreatic cancer. Conditions linked to risk of pancreatic cancer development include certain pancreato-biliary anatomical variants, intraductal papillary mucinous neoplasms, mucinous cystic neoplasm, and familial pancreatic cancer with specific genetic mutations. Early imaging signs of pancreatic cancer can also be incidentally encountered on CT or MRI performed for other indications and they should be promptly recognized by the radiologists in order to avoid delays in the diagnosis. The features include focal pancreatic atrophy, contour deformity, dilation of the main pancreatic duct (MPD), changes in the caliber of the MPD, abrupt interruption of the MPD, and biliary tree dilation. MRI with the adoption of abbreviated protocols has been increasingly evaluated for the follow-up of cystic lesions. Although screening of the general population is not recommended due to the low incidence and high costs, surveillance with MRI can be considered in selected high-risk individuals.

Pancreatic Cystic Lesions: Imaging Techniques and Diagnostic Features

The detection of incidental pancreatic cystic lesions has increased over time. It is crucial to separate benign from potentially malignant or malignant lesions to guide management and reduce morbidity and mortality. The key imaging features used to fully characterize cystic lesions are optimally assessed by contrast-enhanced magnetic resonance imaging/magnetic resonance cholangiopancreatography, with pancreas protocol computed tomography offering a complementary role. While some imaging features have high specificity for a particular diagnosis, overlapping imaging features between diagnoses may require further investigation with follow-up diagnostic imaging or tissue sampling.

The Role of MRI in the Diagnosis of Solid Pseudopapillary Neoplasm of the Pancreas and Its Mimickers: A Case-Based Review with Emphasis on Differential Diagnosis

Solid pseudopapillary neoplasm (SPN) is rare pancreatic tumor occurring most commonly in young females. The typical imaging appearance of SPN is of well-defined, encapsulated, and large heterogeneous tumors, consisting of solid and cystic components due to various degrees of intralesional hemorrhage and necrosis. However, atypical imaging presentation in the form of small solid tumors or uniformly cystic lesions might also be seen, which can be explained by specific pathological characteristics. Other imaging features such as a round shape, the absence of main pancreatic duct dilatation, and slow growth, in combination with vague symptoms, favor the diagnosis of SPNs. Nevertheless, the radiological findings of SPN might overlap with other solid and cystic pancreatic neoplasms, such as neuroendocrine tumors, serous and mucinous neoplasms, and even small pancreatic adenocarcinomas. In addition, a few benign non-tumorous conditions including walled-of-necrosis, and intrapancreatic accessory spleen may also pose diagnostic dilemmas simulating SPNs on imaging studies. The aim of this manuscript is to provide a comprehensive overview of the typical and atypical imaging features of SPNs and to describe useful tips for differential diagnosis with its potential mimickers.

Pancreatic cystic neoplasms and post-inflammatory cysts: interobserver agreement and diagnostic performance of MRI with MRCP

PURPOSE

We aimed to answer several clinically relevant questions; (1) the interobserver agreement, (2) diagnostic performance of MRI with MRCP for (a) branch duct intraductal papillary mucinous neoplasms (BD-IPMN), mucinous cystic neoplasms (MCN) and serous cystic neoplasms (SCN), (b) distinguishing mucinous (BD-IPMN and MCN) from non-mucinous cysts, and (c) distinguishing three pancreatic cystic neoplasms (PCN) from post-inflammatory cysts (PIC).

METHODS

A retrospective analysis was performed at a tertiary referral center for pancreatic diseases on 71 patients including 44 PCNs and 27 PICs. All PCNs were confirmed by surgical pathology to be 17 BD-IPMNs, 13 MCNs, and 14 SCNs. Main duct and mixed type IPMNs were excluded. Two experienced abdominal radiologists blindly reviewed all the images.

RESULTS

Sensitivity of two radiologists for BD-IPMN, MCN and SCN was 88-94%, 62-69% and 57-64%, specificity of 67-78%, 67-78% and 67-78%, and accuracy of 77-82%, 65-75% and 63-73%, respectively. There was 80% sensitivity, 63-73% specificity, 70-76% accuracy for distinguishing mucinous from non-mucinous neoplasms, and 73-75% sensitivity, 67-78% specificity, 70-76% accuracy for distinguishing all PCNs from PICs. There was moderate-to-substantial interobserver agreement (Cohen's kappa: 0.65).

CONCLUSION

Two experienced abdominal radiologists had moderate-to-high sensitivity, specificity, and accuracy for BD-IPMN, MCN, and SCN. The interobserver agreement was moderate-to-substantial. MRI with MRCP can help workup of incidental pancreatic cysts by distinguishing PCNs from PICs, and premalignant mucinous neoplasms from cysts with no malignant potential.

Role of volumetric multiparametric MRI in distinguishing between intraductal papillary mucinous neoplasms and serous cystadenoma

PURPOSE

To evaluate the use of volumetric multiparametric MRI in differentiating pancreatic intraductal papillary mucinous neoplasms (IPMNs) from serous cystadenomas (SCAs) METHODS: Included patients (123 patients with pancreatic cystic neoplasms (PCNs) measuring ≥ 10 mm) were stratified into two groups based on cyst type. Axial cyst size, region of interest (ROI)-based apparent diffusion coefficient (ADC) and volumetric data, including cyst volume, volumetric apparent diffusion coefficient (vADC), and volumetric venous enhancement (vVE) were extracted and compared between the two groups. Univariate and multiple logistic regression was used to develop models for distinguishing between IPMNs and SCAs.

RESULTS

Volume and size of the cysts, vVE and vADC and ROI-ADC were significantly different between the two groups. Cyst volume was significantly larger in SCAs (median = 14.1cm³, IQR 3.5-42.5) than in IPMNs (median = 2.5 cm³, IQR 1.1-6) (p < 0.001). IPMNs had a higher volumetric ADC value in comparison to SCAs (2925 ± 294 × 10^-6 mm²/s vs 2521 ± 202 × 10^-6 mm²/s, p < 0.001). However, IPMNs had lower vVE values compared to SCAs (37 signal intensity (SI) vs 86 SI, p < 0.001). Area under the ROC Curve (AUC) of the model that included vADC and cyst volume had 95% accuracy in distinguishing between the two groups. In comparison, the AUC of the model that included ROI-ADC and axial cyst size had 84% accuracy in distinguishing between the two groups. A threshold of 2615 × 10^-6 mm²/s for volumetric ADC resulted in the identification of IPMNs from SCAs with sensitivity and specificity of 90.8% and 73.5%, respectively.

CONCLUSION

IPMNs had smaller cyst volume, higher volumetric ADC and lower volumetric VE values compared to SCAs. Volumetric multiparametric MRI could be useful in differentiating between the IPMN and SCA groups.

Pearls and pitfalls of imaging features of pancreatic cystic lesions: a case-based approach with imaging-pathologic correlation

A variety of neoplastic and non-neoplastic lesions of the pancreas can present with a predominantly cystic architecture. These lesions are increasingly being detected as incidental findings on routine cross-sectional imaging following technological advances in these techniques and their widespread use. The different histopathological behaviors show various common and uncommon imaging findings, and some cases show similar appearance in spite of different histopathology. Each lesion requires specific management because of the differing risk of progression to malignancy, and an accurate imaging diagnosis is crucial. The typical imaging characteristics that differentiate pancreatic cystic lesions have been well described and fully summarized. However, in addition to a small percentage of cases that shows uncommon imaging findings, a substantial percentage of cystic lesions shows overlapping imaging findings that can lead to radiological misdiagnosis. For appropriate diagnosis and optimal treatment strategy, it is important to know the uncommon and overlapping imaging findings of these lesions, in addition to familiarity with the typical aspects. In this article, we reconfirm the well-known characteristic imaging features of pancreatic cystic lesions and present several diagnostically challenging cases, focusing on the uncommon and overlapping imaging findings.

MRI of mucinous pancreatic cystic lesions: a new updated morphological approach for the differential diagnosis

Pancreatic cystic lesions (PCLs) have been increasingly identified over the past 2 decades due to the widespread use of high-resolution non-invasive abdominal imaging. They cover a vast spectrum, from benign to malignant and invasive lesions, thus they constitute a significant clinical entity. Among PCLs, mucin-producing lesions are those at risk of progression to malignancy. They include mucinous cystic neoplasms (MCN) and intraductal papillary mucinous neoplasms (IPMN). The diagnosis and management of these cystic lesions are a dilemma since there is a significant overlap in the morphology of benign and premalignant lesions. At the moment, there is no single test that will allow a correct diagnosis in all cases. Magnetic resonance (MR) and endoscopic ultrasound (EUS) morphology, with cyst fluid analysis and cytohistology done with EUS-guided procedure are the best techniques that can narrow the differential diagnosis and identify potentially malignant lesions requiring resection from those requiring follow-up only. The purpose of this paper is to present an updated review of MR imaging findings of mucinous PCLs and to provide a new morphological approach that can serve as a practical guide for the diagnosis of these lesions, allowing a more confident characterization and avoiding relevant misdiagnosis. Furthermore, we provide some information about EUS and cystic fluid analysis and cytohistology, since they are diagnostic modalities that radiologists and surgeons should be familiar with.

CT and MR imaging features of pancreatic adenosquamous carcinoma and their correlation with prognosis

PURPOSE

To retrospectively investigate the computed tomography (CT) and magnetic resonance (MR) imaging features of pancreatic adenosquamous carcinoma (PASC) and the association between imaging findings and prognosis.

MATERIALS AND METHODS

CT, MR images of 26 patients with PASC were analyzed. Clinical symptoms, tumor markers, and patients' survival were recorded. Tumor attenuation, enhancement pattern and degree, vessel involvement, adjacent tissue invasion and metastasis were evaluated. The association between imaging features and overall survival (OS) were also assessed using Cox proportional hazards ratio model.

RESULTS

Fourteen masses were found in the head of the pancreas and 12 in the body/tail. The mean tumor size was 4.47 ± 1.76 cm. PASC usually showed ill-defined (96.2%), lobulated (76.9%) and predominantly solid mass (92.3%). Ring enhancement in the peripheral area of the tumor was commonly seen (76.9%). Vessel invasion was seen in 17 cases (65.4%), encasement of adjacent arteries in 7 cases (26.9%), upstream main pancreatic duct (MPD) dilatation in 16 cases (61.5%) and double duct sign in 9 cases (34.6%). Multivariate Cox proportional hazards model demonstrated that patients with vessel invasion may predict a poor prognosis (p = 0.037).

CONCLUSION

PASC tends to be an ill-defined solid mass with peripheral ring enhancement, and relatively poor enhancement in the central area. PASC may also show vessel invasion, vessel encasement and upstream MPD dilatation. Vessel invasion may indicate a poor prognosis.

Imaging findings for mucinous tumors of the abdomen and pelvis

This article aims to describe the imaging findings for mucinous tumors of the abdomen and pelvis, which have a similar appearance on imaging tests regardless of the organ in which they develop. Due to the high water content of mucus, the appearance of these tumors is generally similar to that of water on ultrasonography, computed tomography, and magnetic resonance imaging. Another common feature of mucin-producing tumors is that calcifications are often present. The rupture of these lesions and accumulation of mucinous material in the peritoneal cavity gives rise to pseudomyxoma peritonei. It is important to identify mucinous tumors because they have a different prognosis and clinical course than non-mucinous tumors and require different management. Depending on their anatomic location and their imaging characteristics, the treatment approach varies from follow-up to radical surgery together with chemotherapy or radiotherapy or both.

Radiological Workup of Cystic Neoplasms of the Pancreas

Pancreatic cystic lesions are being detected with increasing frequency because of increased use and improved quality of cross-sectional imaging techniques. Pancreatic cystic lesions encompass non-neoplastic lesions (such as pancreatitis-related collections) and neoplastic tumors. Common cystic pancreatic neoplasms include serous cystadenomas, mucinous cystic neoplasms, intraductal papillary mucinous neoplasms, and solid pseudopapillary tumors. These cystic pancreatic neoplasms may have typical morphology, but at times show overlapping imaging features on cross-sectional examinations. This article reviews the classical and atypical imaging features of commonly encountered cystic pancreatic neoplasms and presents the limitations of current cross-sectional imaging techniques in accurately classifying pancreatic cystic lesions.

Role of diffusion-weighted MR imaging in predicting the grade of nonfunctional pancreatic neuroendocrine tumors

PURPOSE

The purpose of this study was to describe the magnetic resonance imaging (MRI) findings including diffusion-weighted MRI of nonfunctional pancreatic neuroendocrine tumors (PanNETs) and their hepatic metastases, and investigate the relationships between MRI features and histopathological findings for each grade of PanNETs.

MATERIALS AND METHODS

A total of 30 patients were included. There were 14 men and 16 women with a mean age of 61.60±11 (SD) years (range: 31-81years). PanNET lesions were analyzed qualitatively (signal intensities, contrast enhancement, lesion margins, presence of metastasis and characteristics of metastases) and quantitatively (signal intensity ratios, contrast enhancement indices and normalized apparent diffusion coefficient [ADC]). The relationships between MRI findings and histopathological findings were evaluated.

RESULTS

Among 30 nonfunctional PanNETs, 11 were high-grade tumors, 10 were intermediate and 9 were low-grade tumors. All high grade PanNETs showed low to intermediate signal on T2-weighted images and ill-defined borders. All intermediate grade PanNETs had intermediate and 6 low grade PanNETs have high signal on T2-weighted images. Patients with hepatic metastases from high grade PanNETs had cystic component in 8/10 (80%) and wash-out in 7/10 (70%) whereas intermediate grade PanNETs had none (P<0.05). The normalized ADC values of high grade PanNETs was lower than those of intermediate and low grade PanNETs (P<0.05).

CONCLUSION

The presence of cystic component or contrast wash-out in hepatic metastases correlates with high grade PanNETs. The pre-operative MRI combined with DWI has an important role in grading and surgical planning of PanNETs.

Endoscopic Ultrasound Imaging for Diagnosing and Treating Pancreatic Cysts

Cystic pancreatic lesions are increasingly diagnosed owing to the abundant use of cross-sectional imaging. Given their malignant potential, true pancreatic cysts should be considered for resection or periodic follow-up. Cystic lesions of the pancreas (CLPs) require further evaluation and management. Therefore, it is important to establish a solid diagnosis at the time of detection. Endoscopic ultrasound examination is the imaging modality of choice. Fine needle aspiration provides fluid for cytologic, biochemical, and molecular assays to classify lesions and predict biological behavior. This review provides an overview of the diagnosis and management of various types of commonly encountered true CLPs.

Diffusion-Weighted Magnetic Resonance Imaging in Distinguishing Between Mucin-Producing and Serous Pancreatic Cysts

OBJECTIVE

The aim of this study was to evaluate the feasibility and reproducibility of diffusion-weighted imaging in distinguishing between mucin-producing and serous pancreatic cysts.

METHODS

Forty-four pancreatic cysts (43 patients, 27 women; mean age, 57 years; 26 mucin-producing cysts, 18 serous cysts) that underwent histological examination or cyst analysis after diffusion-weighted magnetic resonance imaging were retrospectively reviewed. Three blinded readers independently evaluated signal intensity and apparent diffusion coefficient (ADC). Intraobserver and interobserver agreements were calculated. Fisher exact test and Welch t test were used to compare signal intensity and ADC values, respectively, with pathological results. Receiver operating characteristic analysis was used to determine diagnostic accuracy of various thresholds for ADC. A P value less than 0.05 was considered statistically significant.

RESULTS

Mean ADC values of the mucin-producing cysts were 3.26 × 10, 3.27 × 10, and 3.35 × 10 mm/s for the 3 readers, respectively. Mean ADC values of the serous cysts were 2.86 × 10, 2.85 × 10, and 2.85 × 10 mm/s for the 3 readers, respectively. Differences in ADC values between the 2 cyst groups were 12.4%, 12.9%, and 14.8% for the 3 readers, respectively (P < 0.001). Intraobserver and interobserver agreement was excellent. A threshold ADC of 3 × 10 mm/s resulted in correct identification of cysts in 77% to 81% of cases, with sensitivity and specificity ranging between 84% and 88% and 66% and 72%, respectively.

CONCLUSIONS

Diffusion-weighted imaging may be a helpful tool in distinguishing between mucin-producing and serous pancreatic cysts.

Intraductal papillary mucinous neoplasms and mucinous cystadenomas: current status and recommendations

The real prevalence of pancreatic cystic lesions remains unknown. The malignant potential of some of these lesions remains a cause for significant concern. Thus, it is mandatory to develop a strategy to clearly discriminate those cysts with a potential for malignant transformation from those that do not carry any significant risk. Intraductal papillary mucinous neoplasms and mucinous cystadenomas are mucinous cystic neoplasms with a known malignant potential that have gained greater recognition in recent years. However, despite the numerous studies that have been carried out, their differential diagnosis among other cysts subtypes and their therapeutic approach continue to be a challenge for clinicians. This review contains a critical approach of the current recommendations and management strategies regarding intraductal papillary mucinous neoplasms and mucinous cystadenomas, as well as highlighting the limitations exposed in current guidelines.

Endoscopic ultrasound of pancreatic tumors

Computed tomography (CT) and endoscopic ultrasound (EUS) are the two most effective techniques for the assessment of pancreatic cancers. CT has revolutionized the field of tumor imaging in pancreatic cancer and is now a well-established imaging technique for diagnosis and staging. However, EUS still plays an important role in several situations, especially when the diagnosis is uncertain or when histopathological confirmation of the lesion is needed. Similarly, regarding cystic lesions, magnetic resonance imaging and CT have very good performances but are often inadequate because the diagnosis can be difficult to establish, while the consequences for the patient are major. New biopsy needles, the use of elastography and ultrasonographic contrast agents, and confocal laser endomicroscopy can also provide additional and essential information to improve diagnosis confidence of pancreatic lesions with EUS.

Diffusion-weighted MRI in Crohn's disease: Current status and recommendations

Over the past years, technological improvements and refinements in magnetic resonance imaging (MRI) hardware have made high-quality diffusion-weighted imaging (DWI) routinely possible for the bowel. DWI is promising for the detection and characterization of lesions in Crohn's disease (CD) and has been advocated as an alternative to intravenous gadolinium-based contrast agents. Furthermore, quantification using the apparent diffusion coefficient may have value as a biomarker of CD activity and has shown promise. In this article we critically review the literature pertaining to the value of DWI in CD for detection, characterization, and quantification of disease activity and complications. Although the body of supportive evidence is growing, it is clear that well-designed, multicenter studies are required before the role of DWI in clinical practice can be fully established. J. Magn. Reson. Imaging 2016;44:1381-1396.

Serous microcystic adenoma of the pancreas associated with malrotation and Hirschsprung's disease in an infant

Serous microcystic adenoma of the pancreas is an uncommon tumor in adults, and reported in pediatric patients only a handful of times. The authors present a case of a 6 month patient with incidental finding of a large cystic mass on the tail of the pancreas during an operation for Hirschsprung's disease. Final pathology was consistent with serous microcystic adenoma. This is the second case report describing this lesion in an infant, and the first time it has been associated with Hirschsprung's disease.