Differential diagnosis of pancreatic cancer from other solid tumours arising from the periampullary area on MDCT

Differentiating small (< 2 cm) pancreatic ductal adenocarcinoma from neuroendocrine tumors with multiparametric MRI-based radiomic features

OBJECTIVES

To assess MR-based radiomic analysis in preoperatively discriminating small (< 2 cm) pancreatic ductal adenocarcinomas (PDACs) from neuroendocrine tumors (PNETs).

METHODS

A total of 197 patients (146 in the training cohort, 51 in the validation cohort) from two centers were retrospectively collected. A total of 7338 radiomics features were extracted from T2-weighted, diffusion-weighted, T1-weighted, arterial phase, portal venous phase and delayed phase imaging. The optimal features were selected by the Mann-Whitney U test, Spearman's rank correlation test and least absolute shrinkage and selection operator method and used to construct the radiomic score (Rad-score). Conventional radiological and clinical features were also assessed. Multivariable logistic regression was used to construct a radiological model, a radiomic model and a fusion model.

RESULTS

Nine optimal features were identified and used to build the Rad-score. The radiomic model based on the Rad-score achieved satisfactory results with AUCs of 0.905 and 0.930, sensitivities of 0.780 and 0.800, specificities of 0.906 and 0.952 and accuracies of 0.836 and 0.863 for the training and validation cohorts, respectively. The fusion model, incorporating CA19-9, tumor margins, pancreatic duct dilatation and the Rad-score, exhibited the best performance with AUCs of 0.977 and 0.941, sensitivities of 0.914 and 0.852, specificities of 0.954 and 0.950, and accuracies of 0.932 and 0.894 for the training and validation cohorts, respectively.

CONCLUSIONS

The MR-based Rad-score is a novel image biomarker for discriminating small PDACs from PNETs. A fusion model combining radiomic, radiological and clinical features performed very well in differentially diagnosing these two tumors.

CLINICAL RELEVANCE STATEMENT

A fusion model combining MR-based radiomic, radiological, and clinical features could help differentiate between small pancreatic ductal adenocarcinomas and pancreatic neuroendocrine tumors.

KEY POINTS

Preoperatively differentiating small pancreatic ductal adenocarcinomas (PDACs) and pancreatic neuroendocrine tumors (PNETs) is challenging. Multiparametric MRI-based Rad-score can be used for discriminating small PDACs from PNETs. A fusion model incorporating radiomic, radiological, and clinical features differentiated small PDACs from PNETs well.

Duodenal neuroendocrine neoplasms on enhanced CT: establishing a diagnostic model with duodenal gastrointestinal stromal tumors in the non-ampullary area and analyzing the value of predicting prognosis

OBJECTIVE

To identify CT features and establish a diagnostic model for distinguishing non-ampullary duodenal neuroendocrine neoplasms (dNENs) from non-ampullary duodenal gastrointestinal stromal tumors (dGISTs) and to analyze overall survival outcomes of all dNENs patients.

MATERIALS AND METHODS

This retrospective study included 98 patients with pathologically confirmed dNENs (n = 44) and dGISTs (n = 54). Clinical data and CT characteristics were collected. Univariate analyses and binary logistic regression analyses were performed to identify independent factors and establish a diagnostic model between non-ampullary dNENs (n = 22) and dGISTs (n = 54). The ROC curve was created to determine diagnostic ability. Cox proportional hazards models were created and Kaplan-Meier survival analyses were performed for survival analysis of dNENs (n = 44).

RESULTS

Three CT features were identified as independent predictors of non-ampullary dNENs, including intraluminal growth pattern (OR 0.450; 95% CI 0.206-0.983), absence of intratumoral vessels (OR 0.207; 95% CI 0.053-0.807) and unenhanced lesion > 40.76 HU (OR 5.720; 95% CI 1.575-20.774). The AUC was 0.866 (95% CI 0.765-0.968), with a sensitivity of 90.91% (95% CI 70.8-98.9%), specificity of 77.78% (95% CI 64.4-88.0%), and total accuracy rate of 81.58%. Lymph node metastases (HR: 21.60), obstructive biliary and/or pancreatic duct dilation (HR: 5.82) and portal lesion enhancement ≤ 99.79 HU (HR: 3.02) were independent prognostic factors related to poor outcomes.

CONCLUSION

We established a diagnostic model to differentiate non-ampullary dNENs from dGISTs. Besides, we found that imaging features on enhanced CT can predict OS of patients with dNENs.

Research and analysis on computed tomography signs and clinical characteristics of chronic duodenal papilla mucositis and duodenal papillary carcinoma

Objective: To investigate the computed tomography (CT) findings of chronic duodenal papilla mucositis and duodenal papillary carcinoma, and provide more imaging information for early diagnosis of duodenal malignant diseases.Methods: CT findings and clinical data of 40 patients with chronic duodenal papilla mucositis and 46 patients with duodenal papillary carcinoma were retrospectively analyzed. Observation and measuring of direct duodenal papilla signs (including size, shape, density, enhancement uniformity, etc.), indirect duodenal papilla signs (including pancreaticobiliary dilatation) and clinical indicators (including tumor markers CA19-9, CA125, CEA, blood routine white blood cell count, bilirubin, age, gender, etc.) were carried out according to CT as well as statistical analysis.Results: There were significant differences in duodenal papilla regular morphology, age and CA19-9 (p < .05), and significant differences in duodenal papilla maximum transverse diameter, diameter of common bile duct, diameter of pancreatic duct, total bilirubin, direct bilirubin, and jaundice in duodenal papillary carcinoma group (p < 0.01). There were no significant differences in duodenal papilla enhancement uniformity, plain CT value, arterial CT value, portal CT value, enhancement uniformity, presence or not of calculus at the lower end, gender, CEA, CA125, white blood cell count, and abdominal pain with fever (all p > .05).Conclusion: CT is helpful for the diagnosis of duodenal papilla disease, but the CT findings of patients with duodenal papillary carcinoma tend to be similar to findings of chronic duodenal papilla mucositis, which is easy to lead to misdiagnosis, so comprehensive diagnosis should be made according to the direct and indirect CT signs as well as laboratory and clinical manifestations of duodenal papilla, so as to improve the diagnosis of duodenal papillary carcinoma, and reduce missed diagnosis and misdiagnosis.

Solid pseudopapillary neoplasm of the pancreas in a young male with main pancreatic duct dilatation: A case report

BACKGROUND

Solid pseudopapillary neoplasms (SPNs) are rare tumors of the pancreas. Typically, they occur in young females, often have characteristic imaging features, such as cystic components and calcification, and have few effects on the pancreatic duct.

CASE SUMMARY

A 31-year-old man was admitted to our hospital with the chief complaint of epigastric pain. There was only mild tenderness in his upper abdomen, and blood tests showed only a slight increase in alkaline phosphatase. Contrast-enhanced computed tomography showed a 40-mm-diameter, hypovascular mass in the head of the pancreas, and the main pancreatic duct upstream of the mass was severely dilated. Magnetic resonance imaging showed low intensity on T1-weighted images, with high intensity on T2-weighted image in some parts. Pancreatic ductal adenocarcinoma was the primary differential diagnosis. Portal vein infiltration could not be ruled out, so this case was a candidate for neoadjuvant chemotherapy. Subsequently, endoscopic ultrasound-guided fine needle aspiration was performed, and pathological evaluation and immunostaining suggested a diagnosis of SPN. Thus, pancreatoduodenectomy was performed. One year after the operation, the patient is alive with no recurrence.

CONCLUSION

Main pancreatic duct dilatation is usually a finding of suspected pancreatic cancer. However, pancreatic duct dilatation can occur in SPN depending on the location and growth speed. Therefore, SPN should be considered in the differential diagnosis of tumors with pancreatic duct dilatation, and pathological evaluation by endoscopic ultrasound-guided fine needle aspiration should be actively performed.

Multi-slice spiral CT findings of tubulovillous adenoma of the duodenum

OBJECTIVES

To analyze the appearance of duodenal tubulovillous adenoma on multi-slice spiral CT images to facilitate early diagnosis and treatment to potentially improve prognosis.

METHODS

We retrospectively analyzed clinical data and CT imaging findings of 11 cases of duodenal tubulovillous adenomas, all confirmed by pathology. The location, size, shape, CT density, relationship with surrounding structures, accompanying bile duct obstruction, and enhancement pattern of each lesion were documented.

RESULTS

All 11 lesions occurred in the descending part of the duodenum. Ten cases occurred in the duodenal papilla area. Nine cases had a low-density ring sign or semicircle sign between the lesion and the adjacent normal intestinal wall on axial images. Eight cases had differing degrees of bile duct dilatation, five of which had concomitant pancreatic duct dilatation. Noncontrast images revealed uniform soft tissue density; contrast enhanced images showed moderate, mostly uniform enhancement, with the most enhancement in the venous phase. In the arterial phase, two lesions showed linear enhancing vessels.

CONCLUSIONS

On multi-slice spiral CT imaging, duodenal tubulovillous adenomas have certain characteristics that could be used for clinical diagnosis and treatment.

PRECIS

On multi-slice spiral CT imaging of duodenal tubulovillous adenoma, findings of nodular or cauliflower-like shape, uniform density, uniform moderate enhancement, and a peripheral low-density ring sign could improve diagnostic accuracy.

[Computed tomography in determining the differentiation of ductal adenocarcinoma of pancreatic head]

OBJECTIVE

To evaluate the features of «hypervascular rim», tumor dimensions and density as prognostic factors of differentiation of pancreatic head adenocarcinoma.

MATERIAL AND METHODS

Pancreatoduodenectomy was performed in 311 patients with pancreatic head adenocarcinoma for the period 2013-2019. A retrospective study included 81 patients who met the following criteria: available data of morphological and immunohistological examination indicating tumor grade from Grade 1 to Grade 3, as well as available preoperative CT images in four phases (native, arterial, portal and delayed). Tumor dimensions, density of the pancreas, adenocarcinoma and abdominal aorta by the phases of contrast enhancement were analyzed in all patients. Moreover, we estimated coefficient of relative enhancement change. Perifocal hypervascular enhancement was assessed in arterial and portal phases. Contrast-enhanced MRI was performed in 15 out of 81 patients. MR images were analyzed regarding a hypervascular rim, and the last one was compared with CT images.

RESULTS

There was no significant difference in density values between different tumor grades. Coefficient of relative enhancement change >1 was observed in 63.64% of highly-differentiated tumors. REC ≤1 was found in 85.11% of tumors grade 2 and 82.6% of tumors grade 3 (p=0.005). According to Chi-square test, there was a correlation between tumor differentiation and hypervascular rim (p=0.03). Moderate and low differentiation was observed in 96.42% of tumors with perifocal enhancement. Hypervascular rim was absent in 81.82% of tumors grade 1. Adenocarcinoma grade 2 was found in 85.71% of cases with unclear perifocal enhancement.

CONCLUSION

Preoperative contrast-enhanced CT is valuable to assume the tumor grade in patients with pancreatic head adenocarcinoma due to assessment of hypervascular rim and REC.

Changes in Pancreatic Endocrine Function and Morphology After Pancreaticoduodenectomy: A Comparison Between Pancreatic Head Cancer and Other Pathologies

OBJECTIVES

It is unclear whether the improved glucose metabolism in pancreas head cancer (PHC) patients after pancreaticoduodenectomy is due to the anatomical change or the relief of pancreatic duct obstruction.

METHODS

We divided 170 patients into the PHC group (n = 54, 31.8%) and other pathology (non-PHC) group (n = 116, 68.2%). Glucose metabolic function was evaluated using the glucose tolerance index (GTI), and the pancreatic duct obstruction and dilatation was measured using the pancreatic atrophic index (PAI).

RESULTS

The preoperative GTI was significantly higher in the PHC group (mean [standard deviation {SD}], 0.84 [1.16]) than in the non-PHC group (0.41 [SD, 0.59], P = 0.000). The postoperative GTI decreased significantly in the PHC group but remained unchanged in the non-PHC group. Similarly, the preoperative PAI was higher in the PHC group (0.32 [SD, 0.19]) than in the non-PHC group (0.13 [SD, 0.09], P = 0.000). The postoperative PAI decreased significantly in the PHC group, but not in the non-PHC group.

CONCLUSIONS

The impaired glucose metabolism in PHC can be caused by pancreatic duct obstruction. After pancreaticoduodenectomy, glucose metabolism is improved by the relief of pancreatic duct obstruction, and not by the anatomical change. The patients should be counseled accordingly.

Assessment of tumor heterogeneity: Differentiation of periampullary neoplasms based on CT whole-lesion histogram analysis

PURPOSE

To investigate the utility of whole-lesion histogram analysis from multidetector computed tomography (MDCT) for discrimination of duodenal adenocarcinoma (DAC), pancreatic ductal adenocarcinoma (PDAC) and gastrointestinal stromal tumor (GIST) around the periampullary area.

MATERIALS AND METHODS

171 patients suspicious of periampullary tumors were examined by MDCT (arterial and venous phases) and treated with surgery. A total of 74 patients were finally included in this retrospective study (26 DACs, 20 PDACs, and 28 GISTs). The interobserver agreement was evaluated by intra-class correlation coefficient (ICC) test between two radiologists. Volumetric histogram analysis based on CT Kinetics software was performed on enhanced MDCT images that recorded different histogram parameters of arterial and venous phases, including mean, median, 10th, 25th, 75th, and 90th percentiles, as well as skewness, kurtosis and entropy. The extracted histogram parameters were compared between DAC, PDAC and GIST respectively by Mann-Whitney U tests with Bonferroni corrections. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic ability of each significant parameter and the area under the curve (AUC) was calculated.

RESULTS

The whole-lesion CT histogram analysis demonstrated significant differences between DAC, PDAC, and GIST with different histogram features on both arterial and venous phase scans (all P < 0.05). In the ROC analysis, the 90th percentile of venous phase demonstrated the highest AUC of 0.854 (P < 0.001) for discriminating DAC from PDAC. Excellent discriminators of periampullary tumors were noted among the histogram features, namely the 90th percentile of arterial phase, which demonstrated AUCs of 0.809 and 0.936 (P < 0.001) respectively for distinguishing DAC and PDAC from GIST.

CONCLUSION

The whole-lesion CT histogram analysis could be useful for differential diagnosis of DAC, PDAC and GIST arising from the periampullary area. Further assessment is warranted to investigate the clinical role of histogram analysis based on MDCT.

Differentiation of duodenal gastrointestinal stromal tumors from hypervascular pancreatic neuroendocrine tumors in the pancreatic head using contrast-enhanced computed tomography

PURPOSE

To determine useful contrast-enhanced computed tomography (CE-CT) features in differentiating duodenal gastrointestinal stromal tumors (duodenal GISTs) from hypervascular pancreatic neuroendocrine tumors in the pancreatic head (pancreatic head NETs).

METHODS

Seventeen patients with pathologically confirmed duodenal GISTs and 25 with pancreatic NETs underwent preoperative CE-CT. CT image analysis included tumor size, morphology, and contrast enhancement. Receiver operating characteristic curves were performed, and cutoff values were calculated to determine CT findings with high sensitivity and specificity.

RESULTS

CT imaging showed duodenal GISTs with higher frequencies of tumor central location close to the duodenum and a predominantly solid tumor type when compared with pancreatic head NETs (p < 0.05 for both). Duodenal GISTs were larger than pancreatic head NETs (3.3 ± 0.9 cm vs. 2.5 ± 1.1 cm, p = 0.03). Duodenal GISTs had significantly lower CT attenuation values (112.9 ± 17.9HU vs. 137.4 ± 32.1HU, p < 0.01) at the arterial phase and higher CT attenuation values at the delayed phase (94.3 ± 7.9HU vs. 84.9 ± 10.4HU, p < 0.01) when compared with pancreatic head NETs. A CT attenuation value of ≤ 135 HU at the arterial phase (30 s) was 76% sensitive, 94.1% specific, and 83.3% accurate for the diagnosis of duodenal GISTs, while a CT attenuation value of ≥ 89.5 HU at the delayed phase (120 s) was 93.3% sensitive, 81.8% specific, and 76.2% accurate for the diagnosis of duodenal GISTs.

CONCLUSION

Tumor central location, size, texture, and contrast enhancement are valuable characteristics for the differentiation between duodenal GISTs and hypervascular pancreatic head NETs during preoperative examination.

Surgical treatment of gastrointestinal stromal tumors of the duodenum: a literature review

Background

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumours in the digestive tract. The duodenal GIST (dGIST) is the rarest subtype, representing only 4-5% of all GIST, but up to 21% of the resected ones. The diagnostic and therapeutic management of dGIST may be difficult due to the rarity of this tumor, its anatomical location, and the clinical behavior that often mimic a variety of conditions; moreover, there is lack of consent for their treatment. This study has evaluated the scientific literature to provide consensus on the diagnosis of dGIST and to outline possible options for surgical treatment.

Methods

An extensive research has been carried out on the electronic databases MEDLINE, Scopus, EMBASE and Cochrane to identify all clinical trials that report an event or case series of dGIST.

Results

Eighty-six studies that met the inclusion criteria were identified with five hundred forty-nine patients with dGIST: twenty-seven patients were treated with pancreatoduodenectomy and ninety-six with only local resection (segmental/wedge resections); in four hundred twenty-six patients it is not possible identify the type of treatment performed (pancreatoduodenectomy or segmental/wedge resections).

Conclusions

dGISTs are a very rare subset of GISTs. They may be asymptomatic or may involve symptoms of upper GI bleeding and abdominal pain at presentation. Because of the misleading clinical presentation the differential diagnosis may be difficult. Tumours smaller than 2 cm have a low biological aggressiveness and can be followed annually by endoscopic ultrasound. The biggest ones should undergo radical surgical resection (R0). In dGIST there is no uniformly adopted surgical strategy because of the low incidence, lack of experience, and the complex anatomy of the duodenum. Therefore, individually tailored surgical approach is recommended. R0 resection with 1-2 cm clear margin is required. Lymph node dissection is not recommended due to the low incidence of lymphatic metastases. Tumor rupture should be avoided.

Nonhypervascular pancreatic neuroendocrine tumors: Spectrum of MDCT imaging findings and differentiation from pancreatic ductal adenocarcinoma

PURPOSE

The purpose of our study was to determine contrast-enhanced MDCT features to differentiate nonhypervascular pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal adenocarcinomas (PDACs).

METHODS

and materials: We included 74 patients with PNETs and 80 patients with PDACs who underwent preoperative MDCT. Two radiologists evaluated the morphologic characteristic and enhancement patterns of the tumors. Quantitative and qualitative analysis was performed, including evaluation of tumor size, homogeneity, contrast enhancement pattern, presence of pancreatic duct dilatation and tumor invasion to the adjacent vessels and peripancreatic infiltration. Tumor-to-pancreas enhancement ratio was defined as the Hounsfield units (HU) value of the tumor divided by the HU value of the pancreas. the first group was hypervascular PNETs showing hyperenhancement on arterial phase images and nonhypervascular PNETs, showing iso- or hypoenhancement on arterial phase images. After that, two radiologists estimated the possibilities of PNET or PDAC were for nonhypervascular PNETs.

RESULTS

On the basis of arterial enhancement, 43 PNETs were hypervascular and 31 were nonhypervascular. When compared to PDAC, nonhypervascular PNETs more frequently had well-defined tumor margins, intratumoral cystic components, calcifications and blood vessels and less frequently had main pancreatic duct dilatation, peripancreatic infiltration and vascular invasion (p < 0.01 for all). Nonhypervascular PNETs had higher tumor-to-pancreas enhancement ratio in venous phase (1.02 vs. 0.78, p = 0.012). Nonhypervascular PNETs more often had portal-venous hyperenhancement or persistent isoenhancement, while PDAC more often had persistent hypoenhancement or gradual delayed enhancement (p < 0.001). The absence of pancreatic duct dilatation and portal-venous hyperenhancement or persistent isoenhancement were the independent predictors for nonhypervascular PNETs. (The most accurate MDCT-findings to predict nonhypervascular PNET were the absence of pancreatic duct dilatation and peripancreatic infiltration (79% and 92% accuracy), portal-venous phase hyperenhancement or persistent isoenhancement (77%), the presence of intratumoral blood vessels (77%) and relative enhancement intensity in venous phase >0.9 (76%). Using these criteria, the area under curve for differentiation of PNET from PDAC was 0.906-0.846.

CONCLUSION

Combined assessment of the enhancement and morphologic characteristics can improve the differentiation between nonhypervascular PNETs and PDAC at contrast-enhanced MDCT.

Differentiation of pancreatic neuroendocrine carcinoma from pancreatic ductal adenocarcinoma using magnetic resonance imaging: The value of contrast-enhanced and diffusion weighted imaging

Pancreatic neuroendocrine carcinoma (PNEC) is often misdiagnosed as pancreatic ductal adenocarcinoma (PDAC). This retrospective study differentiated PNEC from PDAC using magnetic resonance imaging (MRI), including contrast-enhanced (CE) and diffusion-weighted imaging (DWI). Clinical data and MRI findings, including the T1/T2 signal, tumor boundary, size, enhancement degree, and apparent diffusion coefficient (ADC), were compared between 37 PDACs and 13 PNECs. Boundaries were more poorly defined in PDAC than PNEC (97.3% vs. 61.5%, p<0.01). Hyper-/isointensity was more common in PNEC than PDAC at the arterial (38.5% vs. 0.0), portal (46.2% vs. 2.7%) and delayed phases (46.2% vs. 5.4%) (all p<0.01). Lymph node metastasis (97.3% vs. 61.5%, p<0.01) and local invasion/distant metastasis (86.5% vs. 46.2%, p<0.01) were more common in PDAC than PNEC. Enhancement degree via CE-MRI was higher in PNEC than PDAC at the arterial and portal phases (p<0.01). PNEC ADC values were lower than those of normal pancreatic parenchyma (p<0.01) and PDAC (p<0.01). Arterial and portal phase signal intensity ratios and ADC values showed the largest areas under the receiver operating characteristic curve and good sensitivities (92.1%–97.2%) and specificities (76.9%–92.3%) for differentiating PNEC from PDAC. Thus the enhancement degree at the arterial and portal phases and the ADC values may be useful for differentiating PNEC from PDAC using MRI.

Functional and morphological evolution of remnant pancreas after resection for pancreatic adenocarcinoma

Functional and morphological evolution of remnant pancreas after resection for pancreatic adenocarcinoma is investigated.The medical records of 45 patients who had undergone radical resection for pancreatic adenocarcinoma from March 2010 to September 2013 were reviewed retrospectively. There were 34 patients in the pancreaticoduodenectomy (PD) group and 10 patients in the distal pancreatectomy (DP) group. One patient received total pancreatectomy. The endocrine function was measured using the glucose tolerance index (GTI), which was derived by dividing daily maximum serum glucose fluctuation by daily minimum glucose. Remnant pancreas volume (RPV) was estimated by considering pancreas body and tail as a column, and head as an ellipsoid, respectively. The pancreatic atrophic index (PAI) was defined as the ratio of pancreatic duct width to total pancreas width. Representative indices of each patient were compared before and after resection up to 2 years postoperatively.The area under receiver operating characteristic curve of GTI for diagnosing DM was 0.823 (95% confidence interval, 0.699-0.948, P < .001). Overall, GTI increased on postoperative day 1 (POD#1, mean ± standard deviation, 1.79 ± 1.40 vs preoperative, 1.02 ± 1.41; P = .001), and then decreased by day 7 (0.89 ± 1.16 vs POD#1, P < .001). In the PD group, the GTI on POD#14 became lower than preoperative (0.51 ± 0.38 vs 0.96 ± 1.37; P = .03). PAI in the PD group was significantly lower at 1 month postoperatively (0.22 ± 0.12 vs preoperative, 0.38 ± 0.18; P < .001). In the PD group, RPV was significantly lower at 1 month postoperatively (25.3 ± 18.3 cm vs preoperative, 32.4 ± 20.1 cm; P = .02), due to the resolution of pancreatic duct dilatation. RPV of the DP group showed no significant change. GTI was negatively related to RPV preoperatively (r = -0.317, P = .04), but this correlation disappeared postoperatively (r = -0.044, P = .62).Pancreatic endocrine functional deterioration in pancreatic adenocarcinoma patients may in part be due to pancreatic duct obstruction and dilatation caused by the tumor. After resection, this proportion of endocrine insufficiency is corrected.

Enhancing pancreatic mass with normal serum CA19-9: key MDCT features to characterize pancreatic neuroendocrine tumours from its mimics

OBJECTIVES

To determine key MDCT features for characterizing pancreatic neuroendocrine tumours (PNET) from their mimics, which manifest as enhancing pancreatic mass with normal serum CA19-9 level.

METHODS

This retrospective study had institutional review board approval and informed consent was waived. Preoperative multiphase MDCT of 74 patients with enhancing pancreatic masses and normal serum CA19-9 levels were included. Surgical pathologies were PNET (n = 42), microcystic serous cystadenomas (m-SCN, n = 12) and solid pseudopapillary epithelial neoplasms (SPEN, n = 20). Two radiologists independently evaluated CT images with a checklist of findings. Frequencies of findings with each disease entity were compared. Diagnostic accuracy was assessed using the key MDCT features alone and in combination. Inter-observer agreement was evaluated.

RESULTS

The most common findings for PNET were mosaic morphological pattern (33/42, 78.6%) and enhancement peak in pancreatic arterial phase (PAP, 32/42, 76.2%), for m-SCN were honeycomb pattern (9/12, 75.0%) and enhancement peak in PAP (10/12, 83.3%) and for SPEN were melting icecream pattern (16/20, 80.0%) and hypo-enhancement in all phases (18/20, 90.0). Using a combination of morphological patterns and enhancement features, PNET was identified with 88% sensitivity and 81% specificity, m-SCN was identified with 83% sensitivity and 94% specificity, and SPEN was identified with 90% sensitivity and 91% specificity. Inter-observer agreement concerning CT findings was good to excellent (κ = 0.68 to 0.81, all p < 0.01).

CONCLUSIONS

Morphological features and enhancement patterns on MDCT are key features for characterizing enhancing pancreatic mass with normal serum CA19-9. PNET could be differentiated from its mimics with high accuracy.

Various diffusion magnetic resonance imaging techniques for pancreatic cancer

Pancreatic cancer is one of the most common malignant tumors and remains a treatment-refractory cancer with a poor prognosis. Currently, the diagnosis of pancreatic neoplasm depends mainly on imaging and which methods are conducive to detecting small lesions. Compared to the other techniques, magnetic resonance imaging (MRI) has irreplaceable advantages and can provide valuable information unattainable with other noninvasive or minimally invasive imaging techniques. Advances in MR hardware and pulse sequence design have particularly improved the quality and robustness of MRI of the pancreas. Diffusion MR imaging serves as one of the common functional MRI techniques and is the only technique that can be used to reflect the diffusion movement of water molecules in vivo. It is generally known that diffusion properties depend on the characterization of intrinsic features of tissue microdynamics and microstructure. With the improvement of the diffusion models, diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique to the more complex. In this review, the various diffusion MRI techniques for pancreatic cancer are discussed, including conventional diffusion weighted imaging (DWI), multi-b DWI based on intra-voxel incoherent motion theory, diffusion tensor imaging and diffusion kurtosis imaging. The principles, main parameters, advantages and limitations of these techniques, as well as future directions for pancreatic diffusion imaging are also discussed.