Multimodality imaging of neoplastic and nonneoplastic solid lesions of the pancreas

Imaging of the Pancreas

The evaluation of pancreatic lesions, from solid pancreatic masses to pancreatic cysts, remains a clinical challenge. Although cross-sectional imaging remains the cornerstone of the initial evaluation of an indeterminate pancreatic lesion, advances in imaging with the advent of endoscopic ultrasound scan, elastography, contrast-enhanced endoscopic ultrasound scan, and probe-based confocal laser endomicroscopy have allowed us to visualize the pancreas in even higher resolution and diagnose premalignant and malignant lesions of the pancreas with improved accuracy. This report reviews the range of imaging tools currently available to evaluate pancreatic lesions, from solid tumors to pancreatic cysts.

Current update on primary pancreatic lymphoma

OBJECTIVE

This article reviews the computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) CT findings of primary and secondary pancreatic lymphomas and discusses the role of endoscopic ultrasound-guided fine needle aspiration in diagnosis and management.

CONCLUSION

Pancreatic lymphoma has certain characteristic imaging features which may help distinguish it from the more common pancreatic adenocarcinoma. It is critical to make an accurate diagnosis, as the management of these two conditions is vastly different.

Pancreatic tumors imaging: An update

Currently, ultrasound (US), computed tomography (CT) and Magnetic Resonance imaging (MRI) represent the mainstay in the evaluation of pancreatic solid and cystic tumors affecting pancreas in 80-85% and 10-15% of the cases respectively. Integration of US, CT or MR imaging is essential for an accurate assessment of pancreatic parenchyma, ducts and adjacent soft tissues in order to detect and to stage the tumor, to differentiate solid from cystic lesions and to establish an appropriate treatment. The purpose of this review is to provide an overview of pancreatic tumors and the role of imaging in their diagnosis and management. In order to a prompt and accurate diagnosis and appropriate management of pancreatic lesions, it is crucial for radiologists to know the key findings of the most frequent tumors of the pancreas and the current role of imaging modalities. A multimodality approach is often helpful. If multidetector-row CT (MDCT) is the preferred initial imaging modality in patients with clinical suspicion for pancreatic cancer, multiparametric MRI provides essential information for the detection and characterization of a wide variety of pancreatic lesions and can be used as a problem-solving tool at diagnosis and during follow-up.

Pancreatic Neuroendocrine Neoplasms: Clinical Value of Diffusion-Weighted Imaging

BACKGROUND/AIMS

Diffusion-weighted imaging (DWI) can depict random motions of water molecules in biological tissues during magnetic resonance (MR) examinations. Few papers have tested its application to pancreatic neuroendocrine neoplasms (PanNENs). The aim of this paper is to assess the clinical value of DWI regarding the identification and characterization of PanNENs and diagnosis of liver metastases.

METHODS

Preoperative MR examinations of 30 PanNEN patients were retrospectively reviewed; 30 patients with pathologically proven pancreatic ductal adenocarcinoma (PDAC) were included to compare the imaging features. Qualitative and quantitative MR features were compared between histotypes. A blinded-reader comparison of diagnostic confidence for PanNENs and liver metastases was conducted on randomized image sets. All results were compared with pathological data.

RESULTS

PanNEN conspicuity was higher on DW images compared to conventional MR sequences. DWI had higher detection rates for PanNENs than had conventional sequences (93.3 vs. 71.1%). Sharp margins and absence of main pancreatic duct/common bile duct dilation and chronic pancreatitis were more common among PanNENs as compared to PDACs. Arterial iso- or hyperenhancement and portal hyperenhancement were more frequent within PanNENs as compared to PDACs. No differences between histotypes were found for quantitative features. Arterial-phase images had the highest interobserver agreement for the diagnosis of PanNEN (Cohen's κ = 0.667). DWI provided the highest detection rate for liver metastases as well as excellent interobserver agreement for the diagnosis of liver metastases (κ = 0.932), with good accuracy (AUC = 0.879-0.869).

CONCLUSION

DWI has clinical value regarding the identification of PanNENs and the diagnosis of liver metastases, while conventional MR sequences are fundamental for their characterization.

Role of magnetic resonance imaging in the detection and characterization of solid pancreatic nodules: An update

Pancreatic ductal adenocarcinoma is the most common malignant tumor of the pancreas. The remaining pancreatic tumors are a diverse group of pancreatic neoplasms that comprises cystic pancreatic neoplasms, endocrine tumors and other uncommon pancreatic tumors. Due to the excellent soft tissue contrast resolution, magnetic resonance imaging (MRI) is frequently able to readily separate cystic from noncystic tumors. Cystic tumors are often easy to diagnose with MRI; however, noncystic non-adenocarcinoma tumors may show a wide spectrum of imaging features, which can potentially mimic ductal adenocarcinoma. MRI is a reliable technique for the characterization of pancreatic lesions. The implementation of novel motion-resistant pulse sequences and respiratory gating techniques, as well as the recognized benefits of MR cholangiopancreatography, make MRI a very accurate examination for the evaluation of pancreatic masses. MRI has the distinctive ability of non-invasive assessment of the pancreatic ducts, pancreatic parenchyma, neighbouring soft tissues, and vascular network in one examination. MRI can identify different characteristics of various solid pancreatic lesions, potentially allowing the differentiation of adenocarcinoma from other benign and malignant entities. In this review we describe the MRI protocols and MRI characteristics of various solid pancreatic lesions. Recognition of these characteristics may establish the right diagnosis or at least narrow the differential diagnosis, thus avoiding unnecessary tests or procedures and permitting better management.

Acquired constricting and restricting lesions of the descending duodenum

The descending duodenum is a structure with distinct pathologic processes and anatomic relationships that requires a systematic approach to the differential diagnosis. Because of its tubular shape and fixed position in the retroperitoneum, both intrinsic duodenal and juxtaduodenal diseases are capable of producing luminal narrowing and obstruction. Duodenal lesions may be located in the mucosa or submucosa. Extraduodenal lesions may originate in adjacent structures--such as the pancreas, liver, gallbladder, colon, and lymph nodes--or from other retroperitoneal structures. Causes of duodenal obstruction include intraluminal masses, such as bezoars; duodenal inflammation, such as as peptic ulcers and Crohn disease; hematomas; and benign or malignant mucosal and intramural tumors. Pancreatic inflammation; tumors; and extrinsic compression caused by gallbladder processes, hepatic masses, retroperitoneal fluid collections, and tumors, including lymphoma, may produce duodenal obstruction. Abdominal radiography, barium studies, multidetector computed tomography, magnetic resonance imaging, and positron emission tomography may be used to depict and characterize duodenal strictures. Integration of imaging, clinical, laboratory, and endoscopic findings plays a major role in establishing a diagnosis of obstructive duodenal strictures.

Hybrid imaging for pancreatic malignancy: clinical applications, merits, limitations, and pitfalls

The role of PET/CT in pancreatic malignancy is evolving with new scientific evidence emerging continuously. PET/CT applications in imaging the pancreas and its organ-specific merits, limitations, and potential pitfalls are still evolving. This article provides an overview of the state-of-the-art applications of PET/CT imaging in evaluating pancreatic malignancy, comparing with conventional imaging modalities, such as contrast-enhanced CT and MRI. Current PET/MRI is also reviewed, along with brief discussion on cost-benefit analysis.

Solid cystic pseudopapillary tumor of pancreas with splenic metastasis: Case report and review of literature

INTRODUCTION

Solid-cystic pseudopapillary tumor of the pancreas is rare and most commonly seen in young women. We present a young women with solid-cystic pseudopapillary tumor of the pancreas and discuss the literature.

PRESENTATION OF CASE

Thirty nine years old female patient with a mass about 12cm in the pancreas with splenic invasion seen in our clinic. After having CT and PET-CT view, patient underwent surgery. Distal pancreatectomy with mass excision and splenectomy was performed. Microscopic examination result was solid cystic pseudopapillary tumor with spleen invasion.

DISCUSSION

Solid-cystic pseudopapillary tumor of the pancreas has cystic solid pseudopapillary structures. Prognosis of tumor is better than other pancreatic tumor. Complete resection of tumor with splenic inclusion is surgical treatment.

CONCLUSION

In case of large slow growing pancreatic tumor with splenic metastasis, solid-cystic pseudopapillary tumor of the pancreas should be considered in the diagnosis. Complete surgical resection is associated with long-term survival even in the presence of metastatic disease. Close follow-up is necessary after surgery.

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

PURPOSE

To investigate CT features and differential diagnosis of pancreatic adenocarcinoma compared to other solid tumours arising in the periampullary area.

MATERIALS AND METHODS

One hundred and ninety-five patients with pathologically proven, solid periampullary tumours, including pancreatic adenocarcinoma (n = 98), neuroendocrine tumours (n = 52), gastrointestinal stromal tumours (n = 31), and solid pseudopapillary neoplasms (n = 14), underwent preoperative CT. Two radiologists reviewed CT features and rated the possibility of pancreatic adenocarcinoma.

RESULTS

Statistically common findings for pancreatic adenocarcinoma included: patient age >50 years; ill-defined margin; completely solid mass; homogeneous enhancement; hypoenhancement on arterial and venous phases; atrophy; and duct dilatation. Statistically common findings for GIST included: heterogeneous enhancement; hyperenhancement on arterial and venous phases; rim enhancement; and prominent feeding arteries. The hyperenhancement on arterial and venous phases is statistically common in NET, and heterogeneous enhancement, hypoenhancement on the arterial and venous phases are statistically common in SPN. Diagnostic performance of CT for differentiating pancreatic adenocarcinomas from other solid periampullary tumours was 0.962 and 0.977 with excellent interobserver agreement (κ = 0.824).

CONCLUSION

CT is useful not only for differentiating pancreatic adenocarcinoma form other solid tumours but also for differentiating between other solid tumours, including NET, SPN, and GIST, arising in the periampullary area.

KEY POINTS

• Periampullary tumours arise within 2 cm of major duodenal papilla. • Many mass-forming periampullary tumours can be completely removed by minimal surgery. • Accurate differentiation of pancreatic adenocarcinoma from other solid tumours is important. • CT is useful for differentiating pancreatic adenocarcinoma from other solid tumours. • CT is useful for characterization of periampullary tumours other than adenocarcinomas.

Diffusion tensor magnetic resonance imaging of the pancreas

PURPOSE

To develop a diffusion-tensor-imaging (DTI) protocol that is sensitive to the complex diffusion and perfusion properties of the healthy and malignant pancreas tissues.

MATERIALS AND METHODS

Twenty-eight healthy volunteers and nine patients with pancreatic-ductal-adenocacinoma (PDAC), were scanned at 3T with T2-weighted and DTI sequences. Healthy volunteers were also scanned with multi-b diffusion-weighted-imaging (DWI), whereas a standard clinical protocol complemented the PDAC patients' scans. Image processing at pixel resolution yielded parametric maps of three directional diffusion coefficients λ1, λ2, λ3, apparent diffusion coefficient (ADC), and fractional anisotropy (FA), as well as a λ1-vector map, and a main diffusion-direction map.

RESULTS

DTI measurements of healthy pancreatic tissue at b-values 0,500 s/mm² yielded: λ1 = (2.65±0.35)×10⁻³, λ2 = (1.87±0.22)×10⁻³, λ3 = (1.20±0.18)×10⁻³, ADC = (1.91±0.22)×10⁻³ (all in mm²/s units) and FA = 0.38±0.06. Using b-values of 100,500 s/mm² led to a significant reduction in λ1, λ2, λ3 and ADC (p<.0001) and a significant increase (p<0.0001) in FA. The reduction in the diffusion coefficients suggested a contribution of a fast intra-voxel-incoherent-motion (IVIM) component at b≤100 s/mm², which was confirmed by the multi-b DWI results. In PDACs, λ1, λ2, λ3 and ADC in both 0,500 s/mm² and 100,500 s/mm² b-values sets, as well as the reduction in these diffusion coefficients between the two sets, were significantly lower in comparison to the distal normal pancreatic tissue, suggesting higher cellularity and diminution of the fast-IVIM component in the cancer tissue.

CONCLUSION

DTI using two reference b-values 0 and 100 s/mm² enabled characterization of the water diffusion and anisotropy of the healthy pancreas, taking into account a contribution of IVIM. The reduction in the diffusion coefficients of PDAC, as compared to normal pancreatic tissue, and the smaller change in these coefficients in PDAC when the reference b-value was modified from 0 to 100 s/mm², helped identifying the presence of malignancy.

Magnetic resonance imaging of less common pancreatic malignancies and pancreatic tumors with malignant potential

Pancreatic tumors are an increasingly common finding in abdominal imaging. Various kinds of pathologies of the pancreas are well known, but it often remains difficult to classify the lesions radiologically in respect of type and grade of malignancy. Magnetic resonance imaging (MRI) is the method of choice for the evaluation of pancreatic pathologies due to its superior soft tissue contrast. In this article we present a selection of less common malignant and potentially malignant pancreatic neoplasms with their characteristic appearance on established MRI sequences with and without contrast enhancement.

Radiology of pancreatic neoplasms: An update

Diagnostic imaging is an important tool to evaluate pancreatic neoplasms. We describe the imaging features of pancreatic malignancies and their benign mimics. Accurate detection and staging are essential for ensuring appropriate selection of patients who will benefit from surgery and for preventing unnecessary surgeries in patients with unresectable disease. Ultrasound, multidetector computed tomography with multiplanar reconstruction and magnetic resonance imaging can help to do a correct diagnosis. Radiologists should be aware of the wide variety of anatomic variants and pathologic conditions that may mimic pancreatic neoplasms. The knowledge of the most important characteristic key findings may facilitate the right diagnosis.

Trans-organ versus trans-mesenteric computed tomography-guided percutaneous fine-needle aspiration biopsy of pancreatic masses: feasibility and safety

AIM

To evaluate the safety and efficacy of computed tomography (CT)-guided percutaneous fine-needle aspiration biopsy (FNAB) of pancreatic masses that traverses the gastrointestinal tract or solid viscera.

MATERIALS AND METHODS

From January 2002 to December 2012, 144 patients underwent 165 CT-guided biopsies of pancreatic masses. Biopsies were performed using a 21 or 22 G needle. Cytology reports, medical records, and procedure details for all patients were retrospectively reviewed to evaluate the biopsy route, complications, and diagnostic accuracy.

RESULTS

Trans-organ biopsies of pancreatic masses were safely performed via a direct pathway traversing the stomach (n = 45), colon (n = 14), jejunum (n = 4), or liver (n = 5). There were five self-limiting mesenteric haematomas along the biopsy route on immediate post-procedure CT and all patients remained asymptomatic. All haematomas occurred after a trans-mesenteric approach rather than passage through abdominal organs. Three patients had acute pancreatitis. There was no significant difference in complications and diagnostic yields between the groups. The sensitivity, specificity, positive predictive value, and negative predictive value of final FNAB cytology for malignancy were 98.3%, 100%, 100% and 71.4%, respectively. The overall accuracy was 98.4%.

CONCLUSION

Percutaneous FNAB using the trans-organ approach is a safe and effective technique to diagnose pancreatic malignancy.

MR cholangiopancreatography of the pancreas and biliary system: a review of the current applications

MR cholangiopancreatography (MRCP) is still a rapidly evolving technique, but it has been already accepted as clinically useful and is widely used to evaluate biliary or pancreatic diseases. The advantages of this technique are that it does not use contrast media or ionizing radiation, it is noninvasive and complication free, and the examination is relatively short. MRCP has high sensitivity and specificity for diagnosing biliary dilatation and for determining the site and cause of stenosis. With further improvements of hardware and technique, MRCP is expected to replace diagnostic endoscopic retrograde cholangiopancreatography to examine the biliary and pancreatic ducts in the near future. The other applications include evaluation of primary sclerosing cholangitis, stenosis after liver transplantation, and bilioenteric anastomoses. This article reviews the current applications of MRCP in the evaluation of the pancreas and the biliary system.

Imaging of pediatric pancreatic neoplasms with radiologic-histopathologic correlation

OBJECTIVE

The purpose of this article is to describe the imaging features of pediatric pancreatic tumors with pathologic correlation. Epithelial and nonepithelial lesions are described. Pancreatic imaging protocols, clinical presentation, and management are also detailed.

CONCLUSION

Pancreatic neoplasms are rare in children and vary widely between benign and malignant causes and between cystic and solid lesions. Epithelial tumors are most common and include solid pseudopapillary tumor, pancreatoblastoma, islet cell neoplasms, and cystic lesions.

A Synchronous Pancreatic Metastasis from Renal Clear Cell Carcinoma, with Unusual CT Characteristics, Completely Regressed after Therapy with Sunitinib

We present a case report of a 75-years-old woman affected by renal clear cell carcinoma with a synchronous pancreatic metastasis and a metachronous lung metastasis. This case has two peculiarities. First the pancreatic metastasis was treated just with medical therapy, that is, Sunitinib, instead of the surgical therapy that is mostly considered. Secondly, the pancreatic lesion showed different characteristics on the computed tomography scan compared to the usual pancreatic metastases from renal clear cell carcinoma. The pancreatic metastasis totally regressed after medical treatment and nowadays, four years after the diagnosis, the patient is disease-free.

Clinical application of 3D VIBECAIPI-DIXON for non-enhanced imaging of the pancreas compared to a standard 2D fat-saturated FLASH

PURPOSE

To compare a fast 3D VIBE sequence with Dixon fat saturation and CAIPIRINHA acceleration techniques (3D VIBE(CAIPI-DIXON)) to a standard 2D FLASH sequence with spectral fat saturation and conventional GRAPPA acceleration technique (2D Flash(GRAPPA-fs)) for non-enhanced imaging of the pancreas.

METHODS AND MATERIALS

In this retrospective, institutional review board-approved intra-individual comparison study, 29 patients (7 female, 22 male; mean age 60.4 ± 20.9 years) examined on a 48-channel 3.0-T MR system (MAGNETOM Skyra VD 13, Siemens Healthcare Sector, Germany) were included. 3D VIBE(CAIPI-DIXON) (TR/TE-3.95/2.5+1.27 ms; spatial resolution-1.2 × 1.2 × 3.0 mm(3); CAIPIRINHA 2 × 2 [1], acquisition time-0:12 min) and 2D Flash(GRAPPA-fs) (TR/TE-195/3.69 ms; 1.2 × 1.2 × 3.0 mm(3); GRAPPA 2, 3 × 0:21 min) sequences were performed in each subject in random order prior to the administration of an intravenous contrast agent. Two radiologists evaluated the images with regard to diagnostic preference. Semi-quantitative signal ratios were calculated for the pancreas versus the liver, spleen, muscle, and visceral fat. Inter-reader agreement was calculated using unweighted Cohen's kappa. Signal ratio results were analyzed using a univariate analysis of variance. Additional signal-to-noise (SNR) measurements were performed in a phantom.

RESULTS

3D VIBE(CAIPI-DIXON) was preferred in 72.4% (both readers) and 2D Flash(GRAPPA-fs) in 3.4%/6.9% (reader 1/2) of cases with a kappa value of 0.756. The main reasons for this preference were homogenous fat saturation with 3D VIBE(CAIPI-DIXON) and reduced motion artifacts due to a faster acquisition, leading to improved delineation of the pancreas. Signal ratios of pancreatic to fat signal for 3D VIBE(CAIPI-DIXON) (10.08 ± 3.48) and 2D Flash(GRAPPA-fs) (6.53 ± 3.07) were statistically different (P<.001). However, no additional statistically significant differences in signal ratios were identified (range: 0.73 ± 0.18 to 1.37 ± 0.40; .514<P<.961). SNR did not statistically significantly differ between the sequences.

CONCLUSION

3D VIBE(CAIPI-DIXON) enables robust pancreatic imaging with a shorter time and improved fat suppression relative to conventional 2D Flash(GRAPPA-fs). At an acquisition time of 12 seconds, 3D VIBE(CAIPI-DIXON) can be obtained in considerably less time than standard fat-saturated VIBE sequences.

Institutional experience with solid pseudopapillary neoplasms: focus on computed tomography, magnetic resonance imaging, conventional ultrasound, endoscopic ultrasound, and predictors of aggressive histology

OBJECTIVE

Solid pseudopapillary neoplasms (SPNs) are low-grade malignancies with an excellent prognosis, albeit with the potential for metastatic disease. This study details our institution's experience with the diagnosis and treatment of SPN, including clinical presentation, multimodality imaging findings, and potential predictors of aggressive tumor behavior.

MATERIALS AND METHODS

The institutional pathology database was searched through for all cases of SPN since 1988, yielding 51 patients. The electronic medical record was searched for clinical and demographic information regarding these patients, including age, sex, presenting symptoms, type of surgery, postoperative length of stay, tumor markers, and postsurgical follow-up. All available imaging data were reviewed, including those of 30 patients who underwent multidetector computed tomography, those of 9 patients who underwent magnetic resonance imaging (MRI), those of 3 patients who underwent conventional ultrasound, and those of 11 patients who underwent endoscopic ultrasound.

RESULTS

A total of 84% of patients were females, with a mean age of only 33 years. Prognosis was excellent, with a mean follow-up of 3 years without recurrence. Only 1 of the 51 patients developed metastatic disease to the liver 8 years after the surgery. On computed tomography, lesions tended to be large (5.3 cm), well circumscribed (29/30), round/oval (20/30), and encapsulated (23/30). The lesions often demonstrated calcification (14/30) and typically resulted in no biliary or pancreatic ductal dilatation. The lesions ranged from completely cystic to completely solid. On MRI, the lesions often demonstrated a T2 hypointense or enhancing capsule (6/9) and demonstrated internal blood products (5/9). The lesions tended to be devoid of vascularity on conventional ultrasound. Ten patients were found to have "aggressive" histology at presentation (T3 tumor, nodal involvement, perineural invasion, or vascular invasion). No demographic, clinical, or multidetector computed tomographic imaging features were found to correlate with aggressive histology.

CONCLUSIONS

Certain imaging features (eg, well-circumscribed mass with calcification, peripheral capsule, internal blood products, and lack of biliary/pancreatic ductal obstruction) on computed tomography and MRI are highly suggestive of the diagnosis of SPN, particularly when visualized in young female patients. However, it is not possible to predict aggressive histology on the basis of imaging findings, clinical presentation, or patient demographic features.

Imaging features of pancreatic tumors in children: 13-year experience at a pediatric tertiary hospital

BACKGROUND

Pancreatic tumors are rare in children, resulting in limited information regarding their frequency and imaging appearances.

OBJECTIVE

To review all pancreatic tumors seen in children over a decade at a large tertiary pediatric institution and to describe multimodality imaging findings.

MATERIALS AND METHODS

We conducted a retrospective review of imaging studies performed in children with pancreatic tumors between January 2000 and December 2012, analyzing imaging features on available US, CT and MR examinations. We reviewed patient charts for clinical features, management and final diagnosis.

RESULTS

We included 23 children in this study. Of these, 12 had solid and papillary epithelial neoplasms (SPEN), 3 had neuroendocrine tumors, 3 had lymphoma, and 1 each had hemangioendothelioma, benign congenital cysts with adipose tissue, dendritic cell sarcoma, metastatic rhabdomyosarcoma, and lipoma. All children with SPEN were teenage girls. SPEN showed characteristic imaging features including well-defined margins with surrounding capsule, solid-cystic components and hemorrhage.

CONCLUSION

Pancreatic tumors are uncommon in children. SPEN is the most common tumor and is seen predominantly in teenage girls and shows characteristic imaging features.

Sarcoidosis of the pancreas mimicking adenocarcinoma

Primary sarcoidosis of the pancreas is extremely rare. Clinical presentation is often identical to that of pancreatic adenocarcinoma. Preoperative diagnosis of primary pancreatic sarcoidosis is always challenging. We present a 52-year-old man who developed weight loss and obstructive jaundice. Abdomino-pelvic CT scan showed a mass in the pancreatic head. After hepatopancreaticobiliary MDT discussion, a Whipple's procedure was attempted but the mass was deemed unresectable due to invasion of the superior mesenteric vein. Upon completion of palliative chemotherapy, repeat imaging showed significant mass shrinkage. A reattempt Whipple's procedure was successfully undertaken. Histology showed changes of chronic pancreatitis and peripancreatic granulomatous inflammation with no evidence of malignancy and a diagnosis of sarcoidosis was made. Owing to the devastating nature of pancreatic adenocarcinoma, any mass in the pancreas must be thoroughly investigated before a definitive diagnosis is made.

Usefulness of 18F-FDG PET/CT in an unusual case of solid-pseudopapillary pancreatic tumor in childhood with aggressive behavior

We report an unusual case of a solid-pseudopapillary pancreatic tumor (SPPT) with aggressive behavior that occurred in a 16-year-old male patient. ¹⁸F fluorodeoxyglucose PET/CT showed increased radiopharmaceutical uptake in a solid mass of the body of the pancreas, in several liver lesions, and in multiple peritoneal implants, corresponding to an SPPT with liver and peritoneal metastases, respectively. Based on PET/CT findings, the patient was referred to chemotherapy. In this unusual case of pediatric SPPT with aggressive behavior, ¹⁸F fluorodeoxyglucose PET/CT has been useful in staging the disease and in treatment planning.

The effect of gadolinium chelate contrast agent on diffusion-weighted imaging of pancreatic ductal adenocarcinoma

BACKGROUND

There are only two studies that discuss the effect of a gadolinium chelate contrast agent on pancreatic diffusion-weighted imaging (DWI). However, both studies only included normal pancreas and/or pancreas with pancreatitis and did not include pancreatic ductal adenocarcinoma (PDA).

PURPOSE

To investigate the effect of gadolinium chelate contrast agent on DWI of PDA.

MATERIAL AND METHODS

Twenty-two patients (13 men, 9 women; mean age 62 years) with histopathologically proven PDA were included in this study. DWI was acquired before and after administration of gadopentetate dimeglumine (Magnevist) with two b-values: 0 and 1000 s/mm(2). The signal intensity (SI), signal-to-noise ratio (SNR), and the apparent diffusion coefficient (ADC) of the lesion were recorded for comparison.

RESULTS

The mean time interval between the initiation of contrast administration and the start of the postcontrast DWI series was 393 s (range, 350-510 s). The SIs and SNRs of lesions of b1000 and b0 images of enhanced images were significantly higher than non-enhanced images (P < 0.001, P < 0.001 for b1000 s/mm(2); P = 0.001, P = 0.001 for b0 s/mm(2)). The ADC of all PDAs revealed no statistically significant difference between non-enhanced and enhanced images (P = 0.709). There was also no significant difference between non-enhanced and enhanced images in subgroups based on grades of differentiation and locations of lesion.

CONCLUSION

With increasing SI and SNR of PDA, intravenous contrast administration does not result in a significant difference in quantitative ADC measurements when comparing precontrast to postcontrast DWI when acquired approximately 6-7 min after administration.

Gastroenteropancreatic neuroendocrine tumors: role of imaging in diagnosis and management

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are a heterogeneous group of neoplasms that arise from cells of the diffuse neuroendocrine system and are characterized by a wide spectrum of clinical manifestations. All NETs are potentially malignant but differ in their biologic characteristics and the probability of metastatic disease. The pathologic classification of these tumors relies on their proliferation and differentiation. In the past decades, several nomenclatures have been proposed to stratify neuroendocrine tumors, but the World Health Organization classification is the one that is most widely accepted and used. The diagnosis of neuroendocrine tumor relies on clinical manifestation, laboratory parameters, imaging features, and tissue biomarkers in a biopsy specimen. With improved understanding of the natural history and lesion biology, management of GEP-NETs has also evolved. Although surgery remains the only potentially curative therapy for patients with primary GEP-NETs, other available treatments include chemotherapy, interferon, somatostatin analogs, and targeted therapies. Recent improvements in both morphologic and functional imaging methods have contributed immensely to patient care. Morphologic imaging with contrast agent-enhanced multidetector computed tomography and magnetic resonance imaging is most widely used for initial evaluation and staging of disease in these patients, whereas functional imaging techniques are useful both for detection and prognostic evaluation and can change treatment planning.

Diagnosis of a solid pseudopapillary neoplasm using EUS-FNA

A woman in her 50s was found to have a pancreatic mass on abdominal ultrasound. The tumor measured 40 mm in diameter and included a cystic lesion and calcification. In this case, we suspected a diagnosis of solid pseudopapillary neoplasm (SPN) due to the findings observed on various images. However, we were unable to exclude the possibility that the lesion was a neuroendocrine tumor. Therefore, we performed endoscopic ultrasound (EUS)-guided fine-needle aspiration (EUS-FNA). In addition, in order to confirm the diagnosis of SPN, we performed minimized resection (segmental pancreatectomy). Obtaining a definitive preoperative diagnosis of SPN using EUS-FNA can guide the surgical approach.

Solid pancreatic lesions: characterization by using timing bolus dynamic contrast-enhanced MR imaging assessment--a preliminary study

PURPOSE

To assess the feasibility of postprocessing dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging timing bolus data by using a three-dimensional radial gradient-echo technique with k-space-weighted image contrast (KWIC) for the characterization of solid pancreatic diseases.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and informed consent was waived. A total of 45 patients suspected of having biliary or pancreatic disease underwent pancreatic MR examination with a 3.0-T imager with a low-dose (2 mL gadopentetate dimeglumine) timing bolus by using the radial KWIC technique. There were 24 patients with pancreatic cancers, eight with pancreatic neuroendocrine tumors (PNETs), three with chronic pancreatitis, and 10 with a normal pancreas. By using a dedicated postprocessing software program for DCE MR imaging, the following perfusion parameters were measured for tumor and nontumorous parenchyma: volume transfer coefficient (K(trans)) and extracellular extravascular volume fraction; the rate constant (k(ep)) and initial area under the concentration curve in 60 seconds (iAUC) were then generated. The perfusion parameters acquired on DCE MR images were compared among the groups by using the analysis of variance test.

RESULTS

K(trans), k(ep), and iAUC values in patients with pancreatic cancer (0.042 min(-1) ± 0.023 [standard deviation], 0.761 min(-1) ± 0.529, and 2.841 mmol/sec ± 1.811, respectively) were significantly lower than in patients with a normal pancreas (0.387 min(-1) ± 0.176, 6.376 min(-1) ± 2.529, and 7.156 mmol/sec ± 3.414, respectively) (P < .05 for all). In addition, k(ep) values of PNETs and normal pancreas also differed (P < .0001), and K(trans), k(ep), and iAUC values of pancreatic cancers and PNETs differed significantly (P < .0001, P = .038, and P < .0001, respectively).

CONCLUSION

Results of timing bolus DCE MR imaging with the radial KWIC sequence from routine examinations can be postprocessed to yield potentially useful perfusion parameters for the characterization of pancreatic diseases.

Pancreatic imaging mimics: part 2, pancreatic neuroendocrine tumors and their mimics

OBJECTIVE

This pictorial essay reviews the imaging appearance of pancreatic neuroendocrine tumors, as well as a number of mimics on CT.

CONCLUSION

Pancreatic neuroendocrine tumors have a distinct appearance, typically characterized by a well-defined hypervascular mass best visualized on arterial phase images. However, a number of other lesions can mimic the CT appearance of pancreatic neuroendocrine tumors, including pancreatic metastases, acinar cell carcinoma, pancreatoblastoma, solitary fibrous tumor, pancreatic hamartoma, serous adenoma, intrapancreatic splenules, exophytic gastrointestinal stromal tumors, and peripancreatic paragangliomas.

Multimodality imaging of pancreatic ductal adenocarcinoma: a review of the literature

BACKGROUND

Accurate pre-operative imaging in pancreatic cancer helps avoid unsuccessful surgical explorations and forewarns surgeons regarding aberrant anatomy. This review aimed to determine the role of current imaging modalities in the diagnosis and determination of resectability of pancreatic and peri-ampullary adenocarcinomas.

METHODS

A systematic search of the scientific literature was carried out using EMBASE, PubMed/MEDLINE and the Cochrane Central Register of Controlled Trials for the years 1990 to 2011 to obtain access to all publications, especially randomized controlled trials, reporting on the diagnostic accuracy of ultrasonography, multi-detector computed tomography (MDCT), magnetic resonance imaging (MRI), endoscopic ultrasonography (EUS) or positron emission tomography (PET)-computed tomography (CT) and the evaluation of resectability of pancreatic and peri-ampullary adenocarcinomas.

RESULTS

Based on 66 articles analysed in the review, MDCT and MRI/MRCP have comparable sensitivity and specificity rates for diagnosis and staging of pancreatic cancers. EUS offers the best sensitivity and specificity rates for lesions <2 cm. Improved staging has been noted when PET-CT scans are added to pre-operative evaluation.

CONCLUSIONS

MDCT with angiography or MRI/MRCP should constitute the first imaging modality in suspected pancreatic adenocarcinomas. EUS is recommended for assessing lesions not clearly detected, but suspected, on CT/MRI and in tumours considered 'borderline resectable' on MDCT to assess vascular involvement. PET-CT in locally advanced lesions will help rule out distant metastases.

Solid-pseudopapillary neoplasms of the pancreas: clinical and pathological features of 33 cases

PURPOSE

Solid-pseudopapillary neoplasms (SPNs) are rare pancreatic tumors, with a low potential for malignancy. The clinical and pathological features of 33 SPNs were reviewed.

METHODS

This study conducted a retrospective analysis of 33 patients who underwent surgery for a pathologically confirmed SPN from 2000 to 2011.

RESULTS

Thirty of the 33 patients (91 %) were female, and the median age at diagnosis was 29.2 years (range 12-59). The most common symptom was abdominal discomfort with dull pain (58 %). Others included asymptomatic lesions that were only detected incidentally during imaging (21 %), a palpable abdominal mass (15 %) and indigestion (6 %). All 33 patients underwent surgery with a curative intent and 3 (9 %) underwent laparoscopic surgery. The mean diameter of the tumors was 4.9 cm (range 2-15 cm), and they occurred in the head (9, 27 %), neck (5, 15 %), body or tail (19, 58 %) of the pancreas. One patient had lymph node metastases, one patient had portal venous invasion and 8 patients had perineural invasion. The patient follow-up ranged from 4 to 118 months, and 32 patients were alive and well without recurrence. One patient relapsed 10 months after distal pancreatectomy with splenectomy and underwent a second surgery via laparotomy. Unfortunately, the patient died of multiple organ failure 12 days after the second surgery.

CONCLUSION

SPNs are rare neoplasms with malignant potential but excellent prognosis. Adequate surgical resection, including laparoscopic surgery, may therefore be performed safely and is associated with a long-term survival, even in invasive cases.

The CT findings of pancreatic acinar cell carcinoma in five cases

OBJECTIVES

The aim of this study is to analyze the computed tomographic (CT) findings of pancreatic acinar cell carcinoma (ACC).

MATERIALS AND METHODS

The CT features and clinical presentations of five patients (four men, one woman; mean age, 52 years) with pathology-proven pancreatic ACC were reviewed. The image characteristics included the lesion location and size, the exophytic nature of the tumor, intratumoral hemorrhage, calcification, the presence of cystic or necrotic components, bile or pancreatic duct dilation, attenuation on the noncontrast image, attenuation on the arterial- and venous-phase images, peripancreatic invasion, peripancreatic lymphadenopathy, and distant metastases.

RESULTS

The tumors were located at the pancreatic tail in three cases and at the pancreatic head in two cases. The average lesion size was 5.3 cm. Exophytic features and cystic/necrotic components were found in 80% (4/5) and 60% (3/5) of cases, respectively. The ACC showed a mild hypodense appearance on noncontrast CT in 100% (3/3) of cases and a hypodense appearance on arterial-/venous-phase CT in 80% (4/5) of cases. The exception was one lesion that showed a significantly hyperdense appearance and a mildly hyperdense appearance on the arterial- and venous-phase images. None of the CT images showed enhancement of a capsule, calcification, intratumoral hemorrhage, bile or pancreatic duct dilation, vascular encasement, or distant metastatic disease, but three cases showed peripancreatic invasion and lymphadenopathy.

CONCLUSIONS

With persistent mild enhancement, the typical ACC appears as an exophytic tumor with a focal cystic/necrotic component and the lack of ductal dilatation. The predilection for older male patients and elevated serum alpha fetoprotein are useful clinical features for confirming an ACC diagnosis.

Unusual solid pancreatic tumors

The vast array of possible histologies for a given pancreatic mass makes the specific diagnosis of a solid pancreatic mass in an individual patient challenging. This article discusses and reviews the imaging findings of those entities that are likely to be encountered in clinical practice, specifically pancreatic endocrine tumors, solid pseudopapillary tumor, secondary pancreatic masses, and heterotopic spleen.