Role of Radiological Imaging in the Diagnosis and Characterization of Pancreatic Cystic Lesions: A Systematic Review

Risk Models for Pancreatic Cyst Diagnosis

The overall prevalence of pancreatic cysts (PCs) is high in the general population. In clinical practice PCs are often incidentally discovered and are classified into benign, premalignant, and malignant lesions according to the World Health Organization. For this reason, in the absence of reliable biomarkers, to date clinical decision-making relies mostly on risk models based on morphological features. The aim of this narrative review is to present the current knowledge regarding PC's morphologic features with related estimated risk of malignancy and discuss available diagnostic tools to minimize clinically relevant diagnostic errors.

Malignancy risk factors and prognostic variables of pancreatic mucinous cystic neoplasms in Chinese patients

BACKGROUND

Pancreatic mucinous cystic neoplasms (MCNs) represent one of the precursor lesions of pancreatic ductal adenocarcinoma, and their detection has been facilitated by advances in preoperative imaging. Due primarily to the rarity of MCNs, however, there is limited knowledge regarding the prognostic variables and high-risk factors for malignant transformation. A more comprehensive and nuanced approach is necessary to fill this gap and provide a basis for improved treatment decisions and patient outcomes.

AIM

To investigate the high-risk factors associated with malignant MCNs and to explore the prognostic factors of MCN with associated invasive carcinoma (MCN-AIC).

METHODS

All cases of resected MCNs from a single high-volume institution between January 2012 and January 2022 were retrospectively reviewed. Only cases with ovarian-type stroma verified by progesterone receptor staining were included. Preoperative features, histological findings and postoperative course were documented. Multivariate logistic regression was employed to investigate variables related to malignancy. Survival analysis was performed using the Kaplan-Meier curve, and the prognostic factors were assessed to evaluate the postoperative course of patients with MCN-AIC.

RESULTS

Among the 48 patients, 36 had benign MCNs, and 12 had malignant MCNs (1 high-grade atypical hyperplasia and 11 MCN-AIC). Age, tumour size, presence of solid components or mural nodules and pancreatic duct dilatation were identified as independent risk factors associated with malignancy. The follow-up period ranged from 12 mo to 120 mo, with a median overall survival of 58.2 mo. Only three patients with MCN-AIC died, and the 5-year survival rate was 70.1%. All 11 cases of MCN-AIC were stage I, and extracapsular invasion was identified as a prognostic factor for poorer outcomes.

CONCLUSION

The risk factors independently associated with malignant transformation of MCNs included age, tumour size, presence of solid components or mural nodules, and pancreatic duct dilatation. Our study also revealed that encapsulated invasion was a favourable prognostic factor in MCN-AIC patients.

CYSTIC PANCREATIC LESIONS: IMAGING VERSUS ANATOMOPATHOLOGICAL FINDINGS-HOW TO IMPROVE DIAGNOSTIC ACCURACY?

BACKGROUND

Pancreatic cystic lesions are a group of pancreatic neoplasms with different behavior and risk of malignancy. Imaging diagnosis and differentiation of these lesions remain a challenge.

AIMS

The aim of this study was to evaluate the agreement between computed tomography and/or magnetic resonance imaging and post-operative pathologic diagnoses of Pancreatic cystic lesions in a University Hospital of São Paulo State.

METHODS

A total of 39 patients with surgically diagnosed Pancreatic cystic lesions were enrolled, as a study cohort from 2009 to 2019. Preoperative radiological and final pathological diagnosis was correlated to measure computed tomography and/or magnetic resonance imaging diagnostic. Pancreatic adenocarcinoma, choledochal pancreatic cyst, mucinous cystadenoma, serous cystadenoma, intraductal papillary mucinous neoplasms, and pancreatic pseudocyst were classified as neoplastic cysts.

RESULTS

It was noted that 27 patients (69.23%) had preoperative computed tomography and magnetic resonance imaging, 11 patients (28.20%) had preoperative computed tomography only, and 1 patient had preoperative magnetic resonance imaging only. The values for diagnoses made only with computed tomography (p=0.47) and from the combination of computed tomography+magnetic resonance imaging (p=0.50) did also point to moderate agreement with the anatomopathological findings. The values pointed to a fair agreement for the diagnosis of mucinous cystadenoma (p=0.3), moderate agreement for intraductal papillary mucinous neoplasms (p= 0.41), good agreement for serous cystadenoma (p=0.79), and excellent agreement for choledochal pancreatic cyst (p=1), pancreatic pseudocyst (p=0.84), and Frantz tumor (p=1) (p<0.05).

CONCLUSIONS

The findings of computed tomography and/or magnetic resonance imaging have an equivalent diagnostic agreement with an anatomopathological diagnosis for differentiating benign from malignant Pancreatic cystic lesions and in suggesting a specific diagnosis. There is no statistical difference between the use of computed tomography alone and computed tomography+magnetic resonance imaging in the improvement of diagnostic accuracy.

"Evolving Trends in Pancreatic Cystic Tumors: A 3-Decade Single-Center Experience With 1290 Resections"

OBJECTIVE

The aim of this study was to describe our institutional experience with resected cystic tumors of the pancreas with emphasis on changes in clinical presentation and accuracy of preoperative diagnosis.

SUMMARY BACKGROUND DATA

Incidental discovery of pancreatic cystic lesions has increased and has led to a rise in pancreatic resections. It is important to analyze surgical outcomes from these procedures, and the prevalence of malignancy, pre-malignancy and resections for purely benign lesions, some of which may be unintended.

METHODS

Retrospective review of a prospective database spanning 3 decades. Presence of symptoms, incidental discovery, diagnostic studies, type of surgery, postoperative outcomes, and concordance between presumptive diagnosis and final histopathology were recorded.

RESULTS

A total of 1290 patients were identified, 62% female with mean age of 60 years. Fifty-seven percent of tumors were incidentally discovered. Ninety-day operative mortality was 0.9% and major morbidity 14.4%. There were 23 different diagnosis, but IPMN, MCN, and serous cystadenoma comprised 80% of cases. Concordance between preoperative and final histopathological diagnosis increased by decade from 45%, to 68%, and is presently 80%, rising in parallel with the use of endoscopic ultrasound, cytology, and molecular analysis. The addition of molecular analysis improved accuracy to 91%. Of misdiagnosed cases, half were purely benign and taken to surgery with the presumption of malignancy or premalignancy. The majority of these were serous cystadenomas.

CONCLUSIONS

Indications and diagnostic work-up of cystic tumors of the pancreas have changed over time. Surgical resection can be performed with very low mortality and acceptable morbidity and diagnostic accuracy is presently 80%. About 10% of patients are still undergoing surgery for purely benign lesions that were presumed to be malignant or premalignant. Further refinements in diagnostic tests are required to improve accuracy.

Lower Interobserver Reliability for Nondimensional Intracystic Features Among Abdominal Radiologists for Characterizing Intraductal Papillary Mucinous Neoplasms Using Magnetic Resonance Imaging

OBJECTIVES

Current guidelines recommend magnetic resonance imaging (MRI)/magnetic resonance cholangiopancreatography (MRCP) for risk stratification of intraductal papillary mucinous neoplasms (IPMNs). We assessed the interobserver agreement among radiologists in evaluating and risk stratifying IPMNs.

METHODS

This single-center study evaluated 30 patients with IPMNs who had undergone MRI/MRCP, endoscopic ultrasound, and/or surgical resection. Six abdominal radiologists evaluated the MRI/MRCPs to document multiple parameters. The analysis applied Landis and Koch κ interpretation for categorical variables and intraclass correlation coefficient (r) for continuous variables.

RESULTS

Radiologists demonstrated almost perfect agreement for location (κ = 0.81, 95% confidence interval [CI], 0.74-0.87), size (r = 0.95; 95% CI, 0.89-0.98), and main pancreatic duct diameter (r = 0.98; 95% CI, 0.96-0.99). Substantial agreement was observed for communication with the main pancreatic duct (κ = 0.66; 95% CI, 0.57-0.75) and classification of IPMN subtype (κ = 0.77; 95% CI, 0.67-0.86). Presence of intracystic nodules (κ = 0.31; 95% CI, 0.21-0.42) and wall thickening (κ = 0.09; 95% CI, -0.01 to 0.18) reached only fair and slight agreement, respectively.

CONCLUSIONS

Although MRI/MRCP is excellent in the evaluation of spatial aspects, there is lower reliability for nondimensional characteristics of IPMNs. These data support guideline-recommended complementary evaluation of IPMNs with MRI/MRCP and endoscopic ultrasound.

Non-inflammatory pancreatic cysts: from diagnosis to treatment (97 cases series)

OBJECTIVE

to describe the implications of the diagnosis and treatment of non-inflammatory pancreatic cysts in a series of patients.

METHODS

we included patients with pancreatic cysts ≥1.0 cm, excluding those with a presumptive diagnosis of a pseudocyst. Imaging tests, echoendoscopy, and histopathology determined the diagnosis of the type of cyst. We applied the guidelines of the International Association of Pancreatology, with some modifications, in patients with mucinous or indeterminate lesions.

RESULTS

97 adult patients participated in the study. A cystic neoplasm of the pancreas was diagnosed in 82.5% of cases. Diagnosis was mainly made by magnetic resonance (46% of cases). The two most common diagnoses were intraductal papillary mucinous neoplasm (43.3%) and serous cystadenoma (26%). Twenty-nine patients underwent surgery (33.3%). The most common surgical procedure was distal pancreatectomy associated with splenectomy in 19 cases (65.5%). Among the operated patients, 11 were diagnosed with cancer. None of the followed, non-operated patients had a diagnosis of cancer.

CONCLUSIONS

magnetic resonance showed good accuracy, particularly in the diagnosis of intraductal papillary mucinous neoplasm. The guidelines of the International Association of Pancreatology, as applied in this study, showed a negative predictive value for cancer of 100%. A development of better diagnostic tests can reduce the number of unnecessary operations.

Diagnostic Yield of Transabdominal Ultrasonography for Evaluation of Pancreatic Cystic Lesions Compared with Endoscopic Ultrasonography

Detection rates of pancreatic cystic lesions (PCLs) have increased, resulting in greater requirements for regular monitoring using imaging modalities. We aimed to evaluate the capability of ultrasonography (US) for morphological characterization of PCLs as a reference standard using endoscopic ultrasonography (EUS). A retrospective analysis was conducted of 102 PCLs from 92 patients who underwent US immediately prior to EUS between January 2014 and May 2017. The intermodality reliability and agreement of the PCL morphologic findings of the two techniques were analyzed and compared using the intraclass correlation coefficient and κ values. The success rates of US for delineating PCLs in the head, body, and tail of the pancreas were 77.8%, 91.8%, and 70.6%, respectively. The intraclass correlation coefficient for US and the corresponding EUS lesion size showed very good reliability (0.978; p < 0.001). The κ value between modalities was 0.882 for pancreatic duct dilation, indicating good agreement. The κ values for solid components and cystic wall and septal thickening were 0.481 and 0.395, respectively, indicating moderate agreement. US may be useful for monitoring PCL growth and changes in pancreatic duct dilation, but it has limited use in the diagnosis and surveillance of mural nodules or cystic wall thickness changes.

The Asian Federation of Societies for Ultrasound in Medicine and Biology (AFSUMB) Guidelines for Contrast-Enhanced Endoscopic Ultrasound

The Asian Federation of Societies for Ultrasound in Medicine and Biology aimed to provide information on techniques and indications for contrast-enhanced harmonic endoscopic ultrasound (CH-EUS), and to create statements including the level of recommendation. These statements are based on current scientific evidence reviewed by a Consensus Panel of 15 internationally renowned experts. The reliability of clinical questions was measured by agreement rates after voting. Six statements were made on techniques, including suitable contrast agents for CH-EUS, differences between contrast agents, setting of mechanical index, dual imaging and duration and phases for observation. Thirteen statements were made on indications, including pancreatic solid masses, pancreatic cancer staging, pancreatic cystic lesions and mural nodules, detection of subtle pancreatic lesions, gallbladder sludge and polyps, hepatic lesions, lymph nodes, subepithelial lesions, visceral vascular diseases, guidance of fine needle aspiration and evaluation for local therapy. These international expert consensus guidelines will assist endosonographers in conducting CH-EUS according to evidence-based information.

Multiparameter Analysis Using 18F-FDG PET/CT in the Differential Diagnosis of Pancreatic Cystic Neoplasms

Purpose

To evaluate multiparametric analysis in differential diagnosis between pancreatic serous cystic neoplasms (SCNs) and mucinous cystic neoplasms (MCNs) as well as the differentiation of the benign and malignant MCNs with ¹⁸F-FDG (18-fluorodeoxyglucose) PET/CT (positron emission tomography).

Methods

Forty patients with total of 41 lesions (SCNs: 27/41; MCNs: 14/41), who were preoperatively examined with ¹⁸F-FDG PET/CT, were retrospectively analyzed. Multiple quantitative parameters using conventional and texture features were included. The combined model was established with complementary PET/MR parameters. The differential diagnostic efficacy of each independent parameter and the combined model were evaluated with receiver operating characteristic (ROC) analysis. Integrated discriminatory improvement (IDI) and net reclassification improvement (NRI) were used to evaluate improvement of diagnostic efficacy by using combination of multiple parameters.

Results

Among all independent parameters, the percentile 5th (0.88 ± 0.38 vs 0.47 ± 0.23, P < 0.001) showed the highest discriminative diagnostic value. The combination of multiple parameters can improve the differential diagnostic efficacy of SCNs and MCNs (sensitivity = 71.4%, specificity = 77.8%, and AUC = 0.788), and the addition of texture parameters to the conventional parameters allowed a significant reclassification with IDI = 0.236 (95% CI: 0.095-0.377) and categorical NRI = 0.434 (95% CI: 0.030-0.838). SURmax (tumor to normal pancreas ratio, T/P) and SURmax (tumor to aorta ratio, T/A) both showed the highest discriminative diagnostic value (sensitivity = 100.0%, specificity = 70.0%, AUC = 0.900, and Youden index = 0.700) in the differential diagnosis of benign and malignant MCNs, with the cutoff values of 0.84 and 0.90, respectively.

Conclusion

Combination of multiple parameters using ¹⁸F-FDG PET/CT could further improve differentiation between pancreatic SCNs and MCNs. SURmax (T/P) and SURmax (T/A) could improve differential diagnosis of benign and malignant MCNs.

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.