[Imaging of neuroendocrine tumors of the pancreas]

Dynamic computed tomography is useful for prediction of pathological grade in pancreatic neuroendocrine neoplasm

BACKGROUND AND AIM

Pathological grading is important in defining the therapeutic strategy in pancreatic neuroendocrine neoplasm (PNEN) but is difficult for unresectable cases. Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) is useful in the diagnosis of PNEN, but its usefulness for pathological grading is not well established. No studies have examined the diagnostic ability of dynamic computed tomography (CT) for pathological grading of PNEN. We investigated the usefulness of EUS-FNA and dynamic CT in the diagnosis and pathological grading of PNEN.

METHODS

In this retrospective study, 39 PNEN patients finally diagnosed via EUS-FNA and/or surgical resection underwent dynamic CT. Pathological samples were diagnosed based on WHO2010; staging was based on the European Neuroendocrine Tumor Society classification. The proportion of the quantification value in the tumor to the pancreatic parenchyma in arterial phase was defined as the CT ratio. Immunohistochemical staining with CD31 was performed to evaluate microvessel density (MVD). We evaluated the relationship between pathological grade, CT ratio, and MVD.

RESULTS

By using EUS-FNA, 35 of 39 (90%) cases were diagnosed as PNEN. As for pathological grade, 15 of 35 (43%) cases could be identified correctly. CT ratio could predict pathological Grade 3 disease. The sensitivity, specificity, and diagnostic accuracy were 100%, 94%, and 95%. MVD was significantly correlated with CT ratio (r = 0.83, P < 0.0001) and pathological grade (P = 0.0074).

CONCLUSIONS

Computed tomography ratio has a relationship with pathological grade in PNEN, which would help decide therapeutic strategy in unresectable cases and cases in which pathological grading is difficult.

[Gastroenteropancreatic endocrine tumors]

CLINICAL/METHODICAL ISSUE

Gastroenteropancreatic neuroendocrine tumors (GEP-NET) are a rare, heterogeneous group of neoplasms. Only 2% of gastrointestinal tumors belong to the group of neuroendocrine neoplasms.

STANDARD RADIOLOGICAL METHODS

A wide spectrum of diagnostic imaging modalities is available: apart from ultrasound not only computed tomography (CT) but also magnetic resonance imaging (MRI) and positron emission tomography CT (PET-CT) play an important role in detection and staging of GEP-NETs.

METHODICAL INNOVATIONS

The PET-CT technique with somatostatin analogues is used for staging as well as for evaluation and monitoring of treatment with peptide radionuclide radiation therapy.

PERFORMANCE

According to the literature NETs of the small bowel with a size over 3 cm can be detected with a sensitivity of 84.7% and a specificity of 96.6% using CT enteroclysis and MR enteroclysis provides the detection of NETs of the small bowel in 93.3% of cases. 'The sensitivity of MRI in detection of pancreatic NETs is between 74% and 100% and is, therefore, higher than CT. Detection of small primary tumors is carried out using PET-CT and seems to be the most sensitive imaging modality to identify the exact location. On the other hand MRI has to be regarded as the best imaging modality for detection of liver metastases compared to CT and PET-CT.

ACHIEVEMENTS

The role of diagnostic imaging is to identify the exact location of the primary tumor and possible metastases, to define an appropriate therapy and to monitor treatment effects; however, the choice of the most appropriate diagnostic imaging modality varies depending on the location and type of the primary tumor.

PRACTICAL RECOMMENDATIONS

The GEP-NETs are predominantly well-vascularized; therefore, dual-phase CT/MR imaging with the arterial and venous phases after contrast media injection is mandatory for detection and localization of primary tumors and metastases. For whole body staging CT and PET-CT should be performed.

Searching for primaries in patients with neuroendocrine tumors (NET) of unknown primary and clinically suspected NET: Evaluation of Ga-68 DOTATOC PET/CT and In-111 DTPA octreotide SPECT/CT

Background

To evaluate the clinical efficacy of In-111 DTPA octreotide SPECT/CT and Ga-68 DOTATOC PET/CT for detection of primary tumors in patients with either neuroendocrine tumor of unknown primary (NETUP) or clinically suspected primary NET (SNET).

Patients and methods.

A total of 123 patients were included from 2006 to 2009, 52 received Ga-68 DOTATOC PET/CT (NETUP, 33; SNET, 19) and 71 underwent In-111 DTPA octreotide SPECT/CT (50; 21). The standard of reference included histopathology or clinical verification based on follow-up examinations.

Results

In the NETUP group Ga-68 DOTATOC detected primaries in 15 patients (45.5%) and In-111 DTPA octreotide in 4 patients (8%) (p < 0.001); in the SNET group, only 2 primaries could be detected, all by Ga-68 DOTATOC. In patients with NETUP, primary tumors could be found significantly more often than in patients with SNET (p = 0.01). Out of these 21 patients 14 patients were operated.

Conclusion

Ga-68 DOTATOC PET/CT is preferable to In-111 DTPA octreotide SPECT/CT when searching for primary NETs in patients with NETUP but should be used with caution in patients with SNET.

[Neuroendocrine carcinoma of the digestive tract: a literature review]

Neuroendocrine carcinoma is a rare and agressive malignant tumor, mainly developing at the expense of the respiratory and of the digestive tract. Among the digestive tract, appendix, small bowel, and pancreas are the preferential sites of involvement, other locations have been more rarely reported. Neuroendocrine digestive tumors may present with various symptoms in relationship with their localization and a complex pathophysiology. Diagnosis is often made at an advanced stage, explaining partly the bad prognosis of these tumors. The optimal management of digestive neuroendocrine tumors is rendered difficult by their rarity and by a low number of randomized trials. We review the literature regarding epidemiologic and prognostic features of these rare tumors, their diagnostic and therapeutic care. Potential complications are also discussed.

Consensus recommendations for the diagnosis and management of well-differentiated gastroenterohepatic neuroendocrine tumours: a revised statement from a Canadian National Expert Group

Well-differentiated neuroendocrine tumours (nets-previously called "carcinoid tumours") are relatively rare tumours originating from the diffuse neuroendocrine system; they are found most often in the bronchial or gastrointestinal systems. In Canada, gastroenterohepatic NETS represent less than 0.25% of oncology cases. Because of the relative rarity of these tumours, diagnostic and therapeutic approaches vary and are often based on individual physician experience. A number of European and North American groups have developed consensus guidelines for the diagnosis and management of well-differentiated gastroenterohepatic NETS, and in 2006, Canadian consensus guidelines were published by a Canadian expert group. The updated and expanded current Canadian guidelines are based on a consensus meeting held in Paris, France, in 2008 and are based on the most current literature.

[Invasive diagnostic procedures for insulinomas of the pancreas]

Insulinomas are the most common cause for hypoglycemia with endogenous hyperinsulinism. Insulinomas are the most frequent endocrine tumor of the pancreas and 10% occur as multiple tumors (e.g. multiple endocrine neoplasia type I) or in rare cases as islet cell hyperplasia. A further 10-15% of insulinomas are malignant. Non-invasive imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography (US) and somatoreceptor scintigraphy (SRN) show a lower sensitivity for detection and localization of tumors, because in many cases insulinomas are smaller than 2 cm in size. Invasive pre-operative diagnostic procedures, such as transhepatic peripancreatic venous blood sampling (TPVB) and the intra-arterial calcium stimulation test (ASVS) are much more time-intensive compared to CT, MRI and US with an examination time of 2-3 h but achieve a more exact pre-operative detection and localization with sensitivities mostly greater than 95% and are therefore the diagnostic methods of choice.

[Tumor-like lesion of the pancreas in chronic pancreatitis : imaging characteristics of computed tomography]

OBJECTIVE

The aim of this study was to describe the imaging findings for inflammatory pseudotumors in patients with chronic pancreatitis as detected in computed tomography (CT).

MATERIALS AND METHODS

In this retrospective study 20 patients with chronic pancreatitis were included, who underwent an abdominal CT scan. In all patients the diagnosis was confirmed by surgery and histopathology. Imaging findings which have previously been described as typical for chronic pancreatitis and for inflammatory pseudotumors were assessed by two radiologists in consensus. Values of tissue density (HU) at CT were measured within the lesions and in the surrounding pancreatic tissue.

RESULTS

In 90% of patients with histologically proven chronic pancreatitis, CT showed corresponding indicative findings. In 10 patients the resected specimen revealed an inflammatory pseudotumor, which was located in all cases within the pancreatic head. Using CT these 10 patients presented with calcifications within the lesion in 50% of the cases, an irregular dilatation of the main pancreatic duct in 90%, a "double duct sign" in 70%, an interrupted main pancreatic duct in the area of the lesion in 50%, a "duct penetrating sign" in 30%, an infiltration of adjacent structures in 10% and pathologically enlarged lymph nodes in 100% of the cases. In the venous contrasting phase six tumors were hypodense and four isodense compared to the surrounding pancreatic tissue. In six patients biphasic CT was performed and the mean difference in attenuation between inflammatory pseudotumors and surrounding parenchyma was significantly higher in the pancreatic phase than in the venous phase.

DISCUSSION

Differentiation between inflammatory pseudotumors and adenocarcinoma remains difficult or even impossible. Typical signs indicative of an adenocarcinoma of the pancreatic head, such as dilatation of the common bile duct and/or the main pancreatic duct as well as enlarged lymph nodes, were also found in patients with inflammatory pseudotumors. Inflammatory pseudotumors showed low contrast between lesions and parenchyma in the venous phase and calcifications within the solid part of the tumor.

Imaging of neuroendocrine tumors

Neuroendocrine tumors may arise from a wide range of organs and may occur in various locations in the body. They include carcinoid tumors, paragangliomas (pheochromocytomas), medullary thyroid carcinomas, and islet cell tumors of the pancreas. In this article the authors focus on the more common tumors with origins primarily in the abdomen, namely carcinoid, paraganglioma, and pancreatic islet cell tumors. Imaging assists in delineating the sites and extent of disease, in preoperative planning for resection of the primary tumor and metastatic disease, and in follow-up. Discussion is restricted to the main imaging modalities used in these tumors: cross-sectional imaging, namely CT and MRI, and nuclear medicine studies.

[Pancreas. Part II: Tumors]

Adenocarcinoma is the most common malignant pancreatic tumor, affecting the head in 60-70% of cases. By the time of diagnosis, approximately 80% of tumors are unresectable. Helical CT is very effective in detection and staging of adenocarcinoma, with a sensitivity of 76-92% for detection and an accuracy of 80-90% for staging, but it has limitations in the detection of small cancers (< or =2 cm). Multidetector CT (MDCT) has brought substantial improvements with its inherent 3D imaging capability. Mangafodipir-enhanced MRI is a problem-solving tool in the depiction of small cancers following an equivocal CT imaging result. Gadolinium-enhanced 3D gradient-echo MRI is helpful in the assessment of vascular invasion of cancer and in determining the etiology of cystic lesions. Serous cystadenoma is benign, has a lobulated contour and contains innumerable small cysts of 0.1-2 cm in diameter. Mucinous cystic neoplasms are unilocular or multilocular (fewer than six cysts), and the cyst diameter exceeds 2 cm. The presence of solid nodular components should alert the radiologist to suspect cystadenocarcinoma. Neuroendocrine tumors are mostly hypervascular. Diagnosis of insulinoma is a challenge: they are <2 cm in 90% of cases and mostly hypervascular at CT or MRI. A combination of contrast-enhanced MDCT, MRI, endosonography, and/or somatostatin receptor scintigraphy is used to detect these small tumors. This review summarizes the imaging features of the most common pancreatic tumors and discusses the limitations of CT, MRI and endosonography.

Multimodality preoperative imaging of pancreatic insulinomas

Pancreatic insulinomas are rare tumours of the islet cells of the pancreas, which account for the majority of functional neuroendocrine tumours of the pancreas. There is often a typical history of recurrent hypoglycaemic collapse and dizzy spells. Insulinomas are usually solitary, and the vast majority are intra-pancreatic in location. They are characteristically small with approximately 66% being less than 2cm at presentation. Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. The role of imaging is to detect and provide precise anatomical localization and staging of tumours prior to surgery. Due to their small size at clinical presentation, they are notoriously difficult to localize radiologically, and specifically designed protocols are necessary to aid detection. In this review, we describe the current "state of the art" imaging protocols that may be used in the preoperative localization of insulinomas.

Hereditary pancreatic endocrine tumours

The two main types of hereditary pancreatic neuroendocrine tumours are found in multiple endocrine neoplasia type 1 (MEN-1) and von Hippel-Lindau disease (VHL), but also in the rarer disorders of neurofibromatosis type 1 and tuberous sclerosis. This review considers the major advances that have been made in genetic diagnosis, tumour localization, medical and surgical treatment and palliation with systemic chemotherapy and radionuclides. With the exception of the insulinoma syndrome, all of the various hormone excess syndromes of MEN-1 can be treated medically. The role of surgery however remains controversial ranging from no intervention (except enucleation for insulinoma), intervening for tumours diagnosed only by biochemical criteria, intervening in those tumours only detected radiologically (1-2 cm in diameter) or intervening only if the tumour diameter is > 3 cm in diameter. The extent of surgery is also controversial, although radical lymphadenectomy is generally recommended. Pancreatic tumours associated with VHL are usually non-functioning and tumours of at least 2 cm in diameter should be resected. Practice guidelines recommend that screening in patients with MEN-1 should commence at the age of 5 years for insulinoma and at the age of 20 years for other pancreatic neuroendocrine tumours and variously at 10-20 years of age for pancreatic tumours in patients with VHL. The evidence is increasing that the life span of patients may be significantly improved with surgical intervention, mandating the widespread use of tumour surveillance and multidisciplinary team management.