Dual-phase helical CT of nonfunctioning islet cell tumors

Pancreatic neuroendocrine tumor: review of heterogeneous spectrum of CT appearance

OBJECTIVE

Pancreatic neuroendocrine tumors (PanNETs) are uncommon pancreatic neoplasms and can be a diagnostic challenge with heterogeneous spectrum of CT appearance. We review CT findings of PanNETs and other mimics.

CONCLUSION

PanNETs are typically hypervascular and have avid enhancement on arterial and venous phase images. However, dedicated pancreas protocol may be needed due to their sometimes atypical appearance including transient enhancement. Careful evaluation of CT findings will help differentiate PanNETs from their mimics, and can be used to establish the diagnosis of a PanNETs. Although an accurate diagnosis can be based on serological, urine, and CT scan findings, confirmation is made via pathological examination.

State-of-the-art Imaging of Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine tumors are rare tumors that present many imaging challenges, from detecting small functional tumors to fully staging large nonfunctioning tumors, including identifying all sites of metastatic disease, particularly nodal and hepatic, and depicting vascular involvement. The correct choice of imaging modality requires knowledge of the tumor type (eg, gastrinoma versus insulinoma), and also the histology (well vs poorly differentiated). Evolving techniques in computed tomography (CT), MRI, endoscopic ultrasonography, and nuclear medicine, such as dual-energy CT, diffusion-weighted MRI, liver-specific magnetic resonance contrast agents, and new nuclear medicine agents, offer new ways to visualize, and ultimately manage, these tumors.

Intravoxel incoherent motion diffusion-weighted imaging of pancreatic neuroendocrine tumors: prediction of the histologic grade using pure diffusion coefficient and tumor size

PURPOSE

The purpose of this study was to assess the value of intravoxel incoherent motion and diffusion-weighted imaging for predicting the histologic grade of pancreatic neuroendocrine tumors (PNETs).

MATERIALS AND METHODS

Forty patients with surgically diagnosed PNETs who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging with a series of 10 b values (0-1000 s/mm(2), were included in this institutional review board-approved retrospective study. The apparent diffusion coefficient (ADC(total)), the intravoxel incoherent motion parameters (pure diffusion coefficient [D], pseudodiffusion coefficient [D(*)], and perfusion fraction [f]) were measured on the tumors. Histologic grading was performed on the basis of the World Health Organization 2010 classification system. Logistic regression analysis and receiver operating curve analysis were performed to identify the significant factors predicting the histologic grades.

RESULTS

Grades 2 and 3 tumors were significantly larger than grade 1 tumors (average 3.62 cm vs 2.17 cm in diameter; P=0.001). Grades 2 and 3 tumors showed significantly lower D values than did grade 1 tumors (0.95 vs 1.21×10(-3) mm(2)/s; P=0.009), although the ADC(total) showed no significant difference. When any of the following 2 criteria was used, (a) tumor size smaller than 2.0 cm in diameter and (b) D value greater than 1.2×10(-3) mm(2)/s, the sensitivity, specificity, and positive predictive value for diagnosing grade 1 PNETs were 76.92%, 100%, and 100%, respectively.

CONCLUSIONS

Pure diffusion coefficient (D) is possibly a better marker than ADC(total) is for differentiating grade 1 from grade 2 or 3 PNET and, combined with tumor size, can predict grade 1 PNET with a high specificity.

Pancreatic endocrine tumors with major vascular abutment, involvement, or encasement and indication for resection

BACKGROUND

Surgery for pancreatic endocrine tumors (PETs) with blood vessel involvement is controversial.

HYPOTHESIS

Resection of PETs with major blood vessel involvement can be beneficial.

DESIGN

The combined databases of the National Institutes of Health and Stanford University hospitals were queried.

MAIN OUTCOME MEASURES

Operation, pathologic condition, complications, and disease-free and overall survival.

RESULTS

Of 273 patients with PETs, 46 (17%) had preoperative computed tomography evidence of major vascular involvement. The mean size for the primary PET was 5.0 cm. The involved major vessel was as follows: portal vein (n = 20), superior mesenteric vein or superior mesenteric artery (n = 16), inferior vena cava (n = 4), splenic vein (n = 4), and heart (n = 2). Forty-two of 46 patients had a PET removed: 12 (27%) primary only, 30 (68%) with lymph nodes, and 18 (41%) with liver metastases. PETs were removed by either enucleation (n = 7) or resection (n = 35). Resections included distal or subtotal pancreatectomy in 23, Whipple in 10, and total in 2. Eighteen patients had concomitant liver resection: 10 wedge resection and 8 anatomic resections. Nine patients had vascular reconstruction: each had reconstruction of the superior mesenteric vein and portal vein, and 1 had concomitant reconstruction of the superior mesenteric artery. There were no deaths, but 12 patients had complications. Eighteen patients (41%) were immediately disease free, and 5 recurred with follow-up, leaving 13 (30%) disease-free long term. The 10-year overall survival was 60%. Functional tumors were associated with a better overall survival (P < .001), and liver metastases decreased overall survival (P < .001).

CONCLUSION

These findings suggest that surgical resection of PETs with vascular abutment/invasion and nodal or distant metastases is indicated.

Intraductal papillary mucinous neoplasm of pancreas: multi-detector row CT with 2D curved reformations--correlation with MRCP

PURPOSE

To retrospectively compare accuracy of multi-detector row computed tomography (CT), combined with two-dimensional (2D) curved reformations, and that of magnetic resonance (MR) cholangiopancreatography (MRCP) for characterization of intraductal papillary mucinous neoplasm (IPMN) as malignant, with pathologic examination as reference standard.

MATERIALS AND METHODS

Institutional review board approval was obtained, informed consent was waived, and study was HIPAA compliant. Twenty-five patients (12 women, 13 men; age range, 44-88 years) with pathologically proved IPMN were examined with dual-phase CT with 1.25-mm-thick sections for pancreatic phase; 2D curved reformations along main pancreatic duct (MPD) were generated. T2-weighted MRCP included thick- and thin-slab single-shot fast spin-echo imaging and transverse fast spin-echo imaging. Two radiologists, blinded to surgical and pathologic findings, evaluated images for lesion location, septa, mural nodules, communication with MPD, extent and diameter of MPD dilatation, calcifications, and vascular encasement. Malignancy was suspected when one of the following was present: MPD diameter larger than 10 mm, mural nodules, vascular encasement, peripancreatic lymphadenopathy, or metastases. Sensitivity and specificity values for prediction of malignancy were calculated for CT and MRCP. Interobserver variability was determined (kappa analysis).

RESULTS

Excellent correlation between modalities was observed. Cyst communication was seen in 20 and 21 of 24 branch pancreatic duct (BPD) IPMNs with CT and MRCP, respectively. Sensitivity, specificity, and accuracy for detection of malignancy were 70%, 87%, and 76% (CT) and 70%, 92%, and 80% (MRCP), respectively. Interobserver agreement was good to perfect for both readers in all comparisons (overall, kappa = 0.70-1.00).

CONCLUSION

CT combined with 2D curved reformation can provide imaging details of IPMN, including communication of BPD IPMN with MPD, that are almost equivalent to those provided at MRCP. Presence of mural nodules, dilated MPD (>10-mm diameter), or thick septa at CT or MRCP may be used as independent predictors of malignancy.

CT in the differentiation of pancreatic neoplasms--progress report

Today, computed tomography (CT) is the most commonly used imaging method in the assessment of pancreatic tumors. The sensitivity of CT in detection of pancreatic tumors is more than 90% when direct and indirect signs are used for diagnosis. However, the potential to differentiate exocrine (non-endocrine) tumors of the pancreas is limited. CT is used in these lesions to perform an adequate staging, especially for surgical purposes. The operative resectability, primarily in regard to vessels, lymph node metastasis and hepatic metastasis, has to be assessed. Keeping in mind the limitations of this macromorphological imaging procedure, CT has the best reproducibility and overall accuracy of all imaging methods. Using multislice CT it is possible to perform non-axial reconstructions with high resolution. In functional endocrine tumors, multislice spiral CT will enhance the diagnostic capabilities, since the whole organ can be examined in thin slices, with high resolution during the rather short arterial phase of the contrast medium. Since some endocrine tumors are hypovascular, a scan during the portovenous phase is recommended too. The diagnosis of benign pancreatic tumors, like serous cystadenoma and pancreatic lipomas, is addressed. The most important pseudotumors of the pancreas are discussed.

Surgical Experience with Nonfunctioning Neuroendocrine Tumors of the Pancreas

Nonfunctioning neuroendocrine tumors of the pancreas are rare slow-growing tumors with a more indolent natural history compared with pancreatic adenocarcinoma. This retrospective report reviews the surgical experience with nonfunctioning neuroendocrine tumors in an academic referral center. Statistical analysis was performed using Student's t test and Kaplan-Meier method compared with log-rank tests. Thirty-eight patients (24 males and 14 females) underwent surgery for a neuroendocrine tumor of the pancreas from 1984 through 1999. Twenty-eight patients with a mean age of 59.9 years had nonfunctioning islet cell tumors and 10 patients with a mean age of 59.1 years had functioning islet cell tumors (four gastrinomas, three glucagonomas, two insulinomas, and one vipoma). The nonfunctioning islet cell tumors were located in the head, neck, or uncinate process in 14 patients (50%), the body in seven (25%), and the tail in seven (25%). Operative procedures for the nonfunctioning islet cell tumors included nine pancreaticoduodenectomies, 12 distal pancreatectomies, three palliative bypasses, and four exploratory laparotomies without a resection or bypass. Mean survival for the four patients explored and not resected or bypassed was 7 months. Median survival for node-negative patients was 124 months, for node-positive patients 75 months, and for patients with metastasis to the liver 9 months. Estimated 2-year actuarial survival for the node-negative patients was 77.8 per cent, for node-positive patients 71.4 per cent, and for patients with metastasis to the liver 36.4 per cent. Six patients (60%) with node-negative disease, three (43%) with node-positive disease, and one (9%) with metastasis to the liver are alive at a mean follow-up of 41.8 months (range 1–167). Significant differences in median survival and 2-year survival were demonstrated between the node-positive/node-negative patients and those with metastasis to the liver ( P = 0.003). Patients with localized nonmetastatic disease should be considered for pancreatic resection as estimated median survival is 75 months or greater. Hepatic metastasis is a major predictor of survival.

Intraductal papillary mucinous tumors of the pancreas: thin-section helical CT findings

OBJECTIVE

The purpose of this study was to evaluate the thin-section helical CT findings of intraductal papillary mucinous tumors and to investigate whether helical CT could distinguish between malignant and benign intraductal papillary mucinous tumors.

MATERIALS AND METHODS

Twenty-seven patients (nine with malignant and 18 with benign intraductal papillary-mucinous tumors) underwent thin-section (3- or 5-mm) helical CT. Two-phase enhanced CT was started 30 and 60-70 sec after injection of contrast material at 3 ml/sec.

RESULTS

In six patients (22.2%), a bulging papilla was depicted on CT. Twenty-five patients (92.6%) had a dilated main pancreatic duct. Cystic lesions were seen in 25 patients (92.6%). Thirteen lesions (48%) were located in the uncinate process, seven (25.9%) were in the head, two (7.4%) were in the body, and three (11%) were in the tail. The cystic lesion was unilocular in five patients (18.5%) and multilocular with a lobulated margin in 20 patients (74%). Communication between the main pancreatic duct and the cystic lesion was depicted in 19 patients (70.4%). The papillary projections corresponding to 3-mm or larger papillary neoplasms were depicted in five patients (18.5%). The bulging papilla was more often observed in malignant than in benign intraductal papillary mucinous tumors (p < 0.05). The caliber of the main pancreatic duct was significantly larger in patients with malignant intraductal papillary mucinous tumors (p > 0.001).

CONCLUSION

The most frequently found feature of intraductal papillary mucinous tumors was a lobulated multilocular cystic lesion located in the uncinate process and in contiguity with the dilated main pancreatic duct. In some patients, a bulging papilla and papillary projections in the ducts, which were specific findings, were visualized on CT. The bulging papilla and the caliber of the main pancreatic duct helped differentiate malignant from benign intraductal papillary mucinous tumors.