The contribution of ultrasonography and computed tomography in the diagnosis of nonfunctioning islet cell tumors of the pancreas

Pancreatic Ultrasound: State of the Art

An ultrasound (US) study is often the first imaging approach in patients with abdominal symptoms or signs related to abdominal diseases, and it is often part of the routine workup. The pancreatic gland, despite its retroperitoneal site, can be efficiently examined with US thanks to advances in US technologies. Nowadays, a pancreatic US study could be considered complete if multiparametric, including the use of Doppler imaging, US elastography, and contrast-enhanced imaging for the study of a pancreatic mass. A complete US examination could contribute to a faster diagnosis, especially if the pancreatic lesion is incidentally detected, addressing second-step imaging modalities correctly.

Contrast-enhanced sonography of nonfunctioning pancreatic neuroendocrine tumors

OBJECTIVE

Diagnosis of malignancy and prognostic assessment continue to be problems in the management of nonfunctioning pancreatic endocrine tumors. Histologic examination is the reference standard. The aim of our study was to compare B-mode and contrast-enhanced sonographic findings regarding nonfunctioning pancreatic endocrine tumors. Signs of malignancy, such as Ki67 index and presence of hepatic metastasis, were considered.

MATERIALS AND METHODS

We retrospectively reviewed the cases of 38 consecutively registered patients with nonfunctioning pancreatic endocrine tumors evaluated with B-mode and contrast-enhanced sonography and resected. At contrast-enhanced sonography all lesions were divided into hypovascular lesions and isovascular or hypervascular lesions. On the basis of homogeneity of enhancement, lesions were classified as homogeneous and inhomogeneous. During the late phase of contrast enhancement, all solid focal hypoechoic liver lesions detected at contrast-enhanced sonography were considered hepatic metastatic lesions. Among pathologic data, grading, mitotic index, and Ki67 index were evaluated. Spearman's test was used to compare contrast-enhanced sonographic enhancement pattern with pathologic grade.

RESULTS

In the arterial phase, 24 of 38 nonfunctioning pancreatic endocrine tumors (63.1%) were hypervascular, seven (18.4%) were isovascular, and seven (18.4%) were hypovascular. Positive correlation was found between contrast-enhanced sonographic findings and Ki67 index (r(s) = 0.62; p < 0.0001). The difference between contrast-enhanced and B-mode sonography in the diagnosis of nonfunctioning pancreatic endocrine tumors was statistically significant (p < 0.05). Use of contrast-enhanced sonography increased diagnostic confidence in the detection of hepatic metastasis. The areas under the receiver operating characteristic curves were 0.916 for B-mode sonography and 1.000 for contrast-enhanced sonography (p < 0.05). There was moderate positive correlation between contrast-enhanced sonographic enhancement pattern and the presence of hepatic metastasis at diagnosis (r(s) = 0.46; p = 0.004) and between Ki67 index and the presence of hepatic metastasis (r(s) = 0.48; p = 0.0022).

CONCLUSION

The contrast-enhanced sonographic enhancement pattern of nonfunctioning pancreatic endocrine tumors has a positive correlation with Ki67 index, which is considered the most reliable independent predictor of the presence of malignancy.

Ultrasonography of the pancreas. 1. Conventional imaging

Ultrasound imaging has made significant advances in recent years and plays an important role in the detection, characterization and staging of pancreatic diseases. Conventional ultrasonography (US) is a noninvasive imaging modality, which continues to be the first diagnostic step in the evaluation of the pancreas. Over its various decades of application, US have detected pancreatic pathology of great diversity. This article reviews the wide utility of US and the many examinations techniques, such as filling the stomach with water, changing the patient's position or suspending inspiration or expiration, allowing us to visualize all portions of the pancreas in a high percentage of patients.

Differential diagnosis of non-functional islet cell tumor and pancreatic carcinoma with sonography

OBJECTIVE

To investigate the differential diagnosis of non-functional islet cell tumor (NFICT) and pancreatic ductal adenocarcinoma (pancreatic carcinoma) with clinical presentation and sonographic features.

MATERIALS AND METHODS

Twenty cases of NFICT were investigated in the study, and 41 cases of pancreatic carcinoma were included as the control group. Among them, 5 NFICT and 32 pancreatic carcinomas underwent CEUS with SonoVue. Clinical presentation and sonographic characteristics were evaluated with Logistic regression analysis. Furthermore, the preliminary result of contrast enhanced ultrasound (CEUS) was analyzed.

RESULTS

Statistic analysis showed four significant factors in differential diagnosis for NFICT and pancreatic carcinoma, including age (P<0.001), tumor size (P=0.006), tumor margin (P<0.001) and vascularity of tumor (P=0.004). Combined these four factors, the sensitivity, specificity and accuracy are 95.0%, 95.1% and 95.1%, respectively. When the patient is younger than 60 years, and tumor is smaller than 5 cm with well-defined margin and hypervascular, it would be most likely a NFICT other than pancreatic carcinoma. NFICT often shows early enhancement and more homogeneous infusion than pancreatic carcinoma on CEUS (P=0.005 and 0.008).

CONCLUSIONS

Sonography is able to provide useful differential information for NFICT, which is often misdiagnosed as pancreatic carcinoma.

Endocrine pancreatic tumours and helical CT: contrast enhancement is correlated with microvascular density, histoprognostic factors and survival

PURPOSE

To assess the role of contrast-enhanced helical CT in the evaluation of tumour vascularity in endocrine pancreatic tumours (EPTs), and to determine the predictive factors of malignancy of EPTs at helical CT with CT-histopathological correlation.

MATERIALS AND METHODS

Thirty-seven consecutive patients with histopathologically proven EPTs underwent dual-phase helical CT. For each tumour detected, its density relative to the surrounding parenchyma was scored on the pancreatic phase using a 5-point scale. Radiological findings were correlated with histopathological (vessel density count) and clinical follow-up findings.

RESULTS

Thirty of 37 patients had non-functioning EPTs and overall 44 tumours were detected by helical CT (mean size 38, range 5-100 mm). CT showed calcifications in 10 tumours. Calcifications were associated with well-differentiated carcinomas (90%, p = 0.02). Vascular density assessed by light microscopy was significantly correlated with tumour enhancement at the pancreatic phase (p = 0.0001). Poorly differentiated carcinomas were less vascularised than well-differentiated tumours and carcinomas (34 vs. 264 vessels/mm2, p = 0.0073). Tumour differentiation also correlated with tumour enhancement at the pancreatic phase (p = 0.0044, trend test): poorly differentiated carcinomas were hypoattenuating (71%) and isoattenuating or weakly hyperattenuating (29%), compared with well-differentiated carcinomas and tumours that were mainly moderately or strongly hyperattenuating (53%). In univariate analysis, poor tumoral differentiation, hepatic metastasis, high mitotic index, poor tumoral enhancement at the pancreatic phase and less vascularised tumours were correlated with decreased survival rate.

CONCLUSION

Enhancement of EPT at CT is correlated with tumour vascularity assessed by light microscopy. Low-enhancing EPT at CT are correlated with poorly differentiated EPT and with a decrease in overall survival.

Differential diagnosis of benign versus malignant nonfunctioning islet cell tumors of the pancreas: the roles of EUS and ERCP

BACKGROUND

Differentiation between benign and malignant nonfunctioning islet cell tumors of the pancreas before surgery is often difficult. The roles of EUS and ERCP were evaluated in the differential diagnosis of these tumors.

METHODS

Seven patients with histologically confirmed nonfunctioning islet cell tumors (4 benign, 3 malignant) underwent EUS and ERCP.

OBSERVATIONS

EUS demonstrated a homogeneous hypoechoic mass or a hypoechoic mass with a regular central echogenic area in the 4 cases of benign tumor, and a hypoechoic mass with an irregular central echogenic area in all 3 cases of malignant tumor. The irregular central echogenic area corresponded to severe hemorrhage, necrosis, or fibrosis with hyalinosis (hyaline degeneration) on pathologic examination. ERCP demonstrated displacement or complete obstruction (because of ductal invasion) of the main pancreatic duct in 2 patients with malignant tumors and no abnormalities in the other 5 cases.

CONCLUSIONS

In patients with nonfunctioning islet cell tumors, a hypoechoic mass with an irregular central echogenic area on EUS or complete obstruction of the main pancreatic duct on ERCP suggests malignancy.

CT findings of non-functioning neuroendocrine pancreatic tumors

Neuroendocrine tumors are rare neoplasms of the pancreas, representing 0.5% of all pancreatic tumors. Approximately, one-third of neuroendocrine tumors are hormonally inactive and called non-functioning neuroendocrine tumors. As these tumors remain clinically silent in their course of growth, they may attain great sizes without causing apparent clinical findings and commonly present in advanced stage. We report three cases of non-functioning neuroendocrine tumors with large sizes and discuss the radiological findings.

Characterization of cystic tumors of the pancreas: CT accuracy

PURPOSE

The purpose of this work was to evaluate the capabilities of CT to accurately characterize cystic tumors of the pancreas.

METHOD

Two observers retrospectively evaluated the CT exams of 100 cystic masses of the pancreas, with pathological confirmation. The two observers, blinded about clinical information and the final diagnosis, tried to categorize the lesions according to well established morphologic features. Statistical analysis was performed to measure the agreement between each radiologist and the consensus diagnosis and to evaluate the usefulness of certain CT findings in differentiating one type of cystic pancreatic neoplasm from another.

RESULTS

Serous cystadenoma was better diagnosed by CT [Youden misclassification index (Ymi) = 0.72] than mucinous cystic tumor (Ymi = 0.44) and solid pseudopapillary tumor (cystic variant) (Ymi = 0.47).

CONCLUSION

As patients with previous history of pancreatitis were excluded from the study, CT findings allowed correct characterization of only 60% of cystic pancreatic masses. Among the remaining 40%, 15-20% of the wrong diagnoses could not be corrected by means of CT, given the patterns shown by the tumors. In 20-25% of the cases, a nonspecific diagnosis of cystic mass was made.

Nonfunctioning islet cell tumors of the pancreas: clinical, imaging and pathological aspects in 16 patients

BACKGROUND

Nonfunctioning islet cell tumors (NFICTs) usually reach a large size prior to detection, at which stage patients have some symptoms or signs. Recently, NFICTs have been discovered in asymptomatic patients with increasing frequency owing to advances in diagnostic imaging techniques. This study investigated clinical, imaging and pathological features in recent cases of NFICT.

METHODS

The medical records, radiographs and pathological specimens of 16 patients with NFICT who were evaluated between April 1991 and March 1996 were reviewed.

RESULTS

Tumor sizes ranged from 0.8 to 17 cm (average, 5.2 cm). Five patients (31%) had some symptoms or signs at the time of diagnosis; however, the other 11 (69%) had no symptoms. Of 10 patients with a tumor of size 5 cm or less, nine were asymptomatic and all tumors were histologically benign. In contrast, in six patients with a tumor larger than 5 cm, four had some symptoms and five tumors were malignant. The detection rates of pancreatic tumor mass on ultrasonography and computed tomography were 94% (15/16) each. All 14 patients in whom the tumor was completely resected survived without recurrence; however, the remaining two patients with liver metastases died following recurrence.

CONCLUSIONS

US and CT are useful in detecting NFICTs even if the tumor is small and the patient is asymptomatic. The detection of NFICTs of small size and their complete removal are essential for a successful cure.

Dual-phase helical CT of nonfunctioning islet cell tumors

PURPOSE

The aim of this study was to evaluate the utility of dual-phase imaging in the assessment of nonfunctioning islet cell tumors (NFITs).

METHOD

Six patients with histologically and biochemically proven NFIT were evaluated by arterial and portal venous dual-phase helical CT. Scan delay was 20 s for the arterial phase and 70 s for the portal phase. Each phase was assessed by consensus reading and specifically evaluated for tumor conspicuity, hepatic metastases, vascular encasement by tumor, and presence of lymphadenopathy.

RESULTS

Overall, tumor conspicuity was greater in the arterial phase (5/6) than in the portal venous phase (1/6) with a mean tumor/normal pancreas attenuation difference of 31.8 HU in the arterial phase compared with 19.2 HU in the portal venous phase. The arterial phase detected a total of 17 liver metastases compared with 9 seen in the portal phase. Lymph node enlargement was noted in three patients, which, although visible in both phases, was more easily discernible in the arterial phase. Venous encasement by tumor was better evaluated on the delayed portal venous phase than the arterial phase.

CONCLUSION

Dual-phase helical CT scanning leads to improvement in the detection and staging of NFITs.

Dual-phase helical CT of nonfunctioning islet cell tumors

PURPOSE

The aim of this study was to evaluate the utility of dual-phase imaging in the assessment of nonfunctioning islet cell tumors (NFITs).

METHOD

Six patients with histologically and biochemically proven NFIT were evaluated by arterial and portal venous dual-phase helical CT. Scan delay was 20 s for the arterial phase and 70 s for the portal phase. Each phase was assessed by consensus reading and specifically evaluated for tumor conspicuity, hepatic metastases, vascular encasement by tumor, and presence of lymphadenopathy.

RESULTS

Overall, tumor conspicuity was greater in the arterial phase (5/6) than in the portal venous phase (1/6) with a mean tumor/normal pancreas attenuation difference of 31.8 HU in the arterial phase compared with 19.2 HU in the portal venous phase. The arterial phase detected a total of 17 liver metastases compared with 9 seen in the portal phase. Lymph node enlargement was noted in three patients, which, although visible in both phases, was more easily discernible in the arterial phase. Venous encasement by tumor was better evaluated on the delayed portal venous phase than the arterial phase.

CONCLUSION

Dual-phase helical CT scanning leads to improvement in the detection and staging of NFITs.

Serous cystadenoma of the pancreas: report of 30 cases with emphasis on the imaging findings

PURPOSE

Our goal was to evaluate retrospectively 30 cases of serous cystadenoma (SCA) to determine its main imaging features as well as to discuss the differential diagnosis problems versus the other cystic lesions of the pancreas.

METHOD

Thirty SCAs were analyzed; they were all benign lesions, proven at surgery. Twenty-three tumors were evaluated with US, 26 with CT, and 5 with MRI.

RESULTS

Three different morphostructural patterns were identified: microlacunar (n = 19), mixed (n = 6), and macrolacunar (n = 5). The diagnosis of SCA, possible in either the microlacunar or the mixed patterns, was achieved in 74% of cases with US (17/23) and in 61.5% with CT (16/26). Among the 19 patients evaluated with both modalities, the joint information allowed a correct diagnosis in 16 cases (84%). The five macrolacunar tumors were undistinguishable from other cystic masses of the pancreas.

CONCLUSION

The diagnosis of SCA can be considered certain in the microlacunar, likely in the mixed, and not possible in the macrolacunar type.

CT of pancreatic neoplasms. Part II: The unusual tumors

The pancreas gives rise to a remarkable variety of neoplasms other than ductal adenocarcinoma. Although no individual type of tumor in this category is prevalent enough to qualify as common, most types are currently encountered with a frequency far greater than that in decades of the recent past. This change is largely the result of the expanded use of contemporary abdominal imaging. The unusual tumors of the pancreas vary greatly in their biologic behavior and, accordingly, in their clinical consequences and therapeutic requirements. Accurate diagnosis, therefore, can be of considerable clinical relevance. Not only is it worthwhile to distinguish one type of unusual pancreatic tumors from another, it is perhaps of even greater consequence to distinguish the unusual tumors from ordinary pancreatic adenocarcinomas. The goals of this discussion are to expand radiologic awareness of these uncommon but interesting pancreatic neoplasms and to increase familiarity with their diagnostically salient features.

The visualization of gastroenteropancreatic endocrine tumors

In this review, we evaluate radiological techniques currently used to localize gastroenteropancreatic (GEP) endocrine tumors. We also describe the visualization, using intravenous (IV) administration of two isotope-labeled somatostatin analogues (123I-Tyr3-octreotide and 111In-DTPA-octreotide) of islet-cell tumors in 25 patients and carcinoids in 39 patients. The primary tumor and previously unrecognized distant metastases were visualized in 20 of the 25 patients (80%) and in 37 of the 39 patients (95%). Parallel in vitro detection of somatostatin receptors on those tumors also visualized in vivo showed that ligand binding to the tumor in vivo represents binding to specific somatostatin receptors. The detection of somatostatin receptors on tumors in vivo predicted a good suppressive effect of octreotide on hormonal hypersecretion by these tumors. It is an easy, quick, and harmless procedure that is valuable in the localization of primary endocrine pancreatic tumors and their often radiologically and clinically unrecognized metastases. Future prospective controlled studies comparing this procedure with other radiological investigative techniques should demonstrate its sensitivity and specificity and determine the place of somatostatin receptor imaging in the localization of GEP endocrine tumors.

Cystic islet cell tumors of the pancreas. A clinico-pathological report of two nonfunctioning cases and review of the literature

Cystic islet cell tumors of the pancreas are extremely rare. The authors report their personal experience with two cases of nonfunctioning cystic endocrine neoplasms. The tumor was diagnosed preoperatively in one case by ultrasonography (US)-guided fine-needle aspiration cytology, while in the other it was identified only in the surgical specimen after a clinical-radiologic diagnosis of pancreatic mucinous cystic tumor. Immunohistochemical assay showed positivity for the generic neuroendocrine markers (neuron specific enolase, or NSE, synaptophysin, and chromogranin A) in both cases and also for glucagon in one case. The neoplasms were resected by distal pancreatectomy with splenectomy and intermediate pancreatectomy respectively. Both patients are alive and recurrence-free 6 mo and 2.5 yr, respectively, after surgery. The authors also review the existing literature, discussing the pathogenesis of such tumors and the imaging techniques and surgical strategies adopted in their management.

Cystic tumors of the pancreas: evaluation by ultrasonography and computed tomography

The personal series of 30 cystic tumors of the pancreas [12 serous cystic tumors (SCT) and 18 mucinous cystic tumors (MCT)] is presented. All neoplasms were evaluated with ultrasonography (US) 28 of 30 with computed tomography (CT); the tumoral histotype could be correctly defined in 73% of cases (seven of 12 SCT and 15 of 18 MCT). Percutaneous fine-needle aspiration (FNA) with diagnostic aims (preparation of cytological smears and/or biochemical assays) was performed in only 10 of 30 cases, yielding a 100% sensitivity; on the whole, the combined use of imaging modalities and FNA allowed correct characterization of the cystic tumors in 27 of 30 cases (90%). The usefulness of a precise diagnostic workup of these neoplasms is emphasized, due to their prognostic and therapeutic outcome.