Small serotonin-producing neuroendocrine tumor of the pancreas associated with pancreatic duct obstruction

Benign Islet Cells Within Peripancreatic Lymph Nodes: A Potential Diagnostic Pitfall

The presence of epithelial cells within lymph node parenchyma is typically indicative of a metastatic malignancy. However, there are rare instances in which non-neoplastic epithelial or epithelioid cells may be found within lymph nodes, either due to aberrant embryologic migration, mechanical displacement, or physiological trafficking. These can potentially lead to serious potential diagnostic pitfalls, as when such situations are encountered by surgical pathologists, there is substantial risk of overdiagnosing these as metastatic malignancy. Herein, we describe 2 cases of benign pancreatic islet cells within peripancreatic lymph nodes, and underscore the potential for misdiagnosis of this phenomenon as foci of metastatic well-differentiated neuroendocrine tumor. The benign nature of these intranodal islet cells was supported by: (1) the absence of a well-differentiated neuroendocrine tumor in the entirely submitted concomitant pancreatic resection specimen and (2) the presence of an admixture of insulin and glucagon expressing cells by immunohistochemistry in a distribution characteristic of non-neoplastic pancreatic islets. Both cases were incidental microscopic findings in pancreatic resections for intraductal papillary mucinous neoplasms that were previously biopsied and showed associated microscopic areas of fibrosis and chronic pancreatitis and thus this phenomenon may be related to mechanical displacement from prior injury and/or biopsy.

Distinctive Pathology Associated With Focal Stenosis of the Main Pancreatic Duct Secondary to Remote Trauma: A Long-term Complication of Seat Belt Pancreatitis

The radiologic finding of focal stenosis of the main pancreatic duct is highly suggestive of pancreatic cancer. Even in the absence of a mass lesion, focal duct stenosis can lead to surgical resection of the affected portion of the pancreas. We present four patients with distinctive pathology associated with non-neoplastic focal stenosis of the main pancreatic duct. The pathology included stenosis of the pancreatic duct accompanied by wavy, acellular, serpentine-like fibrosis, chronic inflammation with foreign body-type giant cell reaction, and calcifications. In all cases, the pancreas toward the tail of the gland had obstructive changes including acinar drop-out and interlobular and intralobular fibrosis. Three of the four patients had a remote history of major motor vehicle accidents associated with severe abdominal trauma. These results emphasize that blunt trauma can injure the pancreas and that this injury can result in long-term complications, including focal stenosis of the main pancreatic duct. Pathologists should be aware of the distinct pathology associated with remote trauma and, when the pathology is present, should elicit the appropriate clinical history.

Giant dilatation of pancreatic duct associated with congenital anomaly of the pancreatic ductal system and small neuroendocrine tumor

Dilatation of the main pancreatic duct (MPD) ˃50 mm is a rare phenomenon. We present the case of successful surgical treatment a 63-year-old female patient who presented epigastric pain and weight loss of 10 kg in 6 months. Based on preoperative examination, the dilatation of MPD was 75 mm. The preliminary diagnosis was main duct intraductal papillary mucinous neoplasm. Extended pylorus-preserving pancreatoduodenectomy with resection of the body of the pancreas was performed. According to the results of pathological and immunohistochemical studies, performed by independent experts, the final diagnosis of congenital anomaly of the ductal system and neuroendocrine tumor of the accessory pancreatic duct was made.

Pancreatic Cancer and Its Mimics

Pancreatic ductal adenocarcinoma (PDAC) is the most common primary pancreatic malignancy, ranking fourth in cancer-related mortality in the United States. Typically, PDAC appears on images as a hypovascular mass with upstream pancreatic duct dilatation and abrupt duct cutoff, distal pancreatic atrophy, and vascular encasement, with metastatic involvement including lymphadenopathy. However, atypical manifestations that may limit detection of the underlying PDAC may also occur. Atypical PDAC features include findings related to associated conditions such as acute or chronic pancreatitis, a mass that is isointense to the parenchyma, multiplicity, diffuse tumor infiltration, associated calcifications, and cystic components. Several neoplastic and inflammatory conditions can mimic PDAC, such as paraduodenal "groove" pancreatitis, autoimmune pancreatitis, focal acute and chronic pancreatitis, neuroendocrine tumors, solid pseudopapillary neoplasms, metastases, and lymphoma. Differentiation of these conditions from PDAC can be challenging due to overlapping CT and MRI features; however, certain findings can help in differentiation. Diffusion-weighted MRI can be helpful but also can be nonspecific. Accurate diagnosis is pivotal for guiding therapeutic planning and potential outcomes in PDAC and avoiding biopsy or surgical treatment of some of these mimics. Biopsy may still be required for diagnosis in some cases. The authors describe the typical and atypical imaging findings of PDAC and features that may help to differentiate PDAC from its mimics. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Zins in this issue.

An Overview of Pancreatic Neuroendocrine Tumors and an Update on Endoscopic Techniques for Their Management

The growing importance of advanced endoscopy in the diagnosis and treatment of pancreatic neuroendocrine neoplasms (PanNETs) necessitates a comprehensive understanding of various biochemical markers, genetic testing methods, radiological techniques, and treatment approaches that encompass multiple disciplines within and beyond gastrointestinal oncology. This review aims to highlight key aspects of these topics, with a specific focus on emerging EUS-guided procedures for the management of PanNETs.

Pediatric Pancreatic Endocrine Tumor Presenting as Acute Pancreatitis: A Case Report

Pancreatic neuroendocrine tumors (PNETs) are relatively rare, especially in the pediatric age group. This report describes a pediatric case of acute pancreatitis secondary to stenosis of the main pancreatic duct due to a PNET. The patient was a boy, thirteen and a half years old, who presented with persistent low-grade fever, nausea, and abdominal pain. He was diagnosed with acute pancreatitis based on the elevation of serum pancreatic enzyme levels and abdominal ultrasonography findings of enlargement of the pancreas and dilatation of the main pancreatic duct. Abdominal contrast-enhanced computed tomography (CT) showed a 5.5 mm, contrast-enhanced mass in the head of the pancreas. His symptoms resolved with conservative treatment, although the pancreatic tumor grew slowly. At fifteen years and four months, since the tumor had enlarged to 8.0 mm, the patient underwent pancreaticoduodenectomy for therapeutic and diagnostic purposes. Based on the pathological evaluation, he was diagnosed with PNET (grade: G1). The patient has been free of tumor recurrence for 10 years and requires no additional therapy. In this report, the clinical characteristics of PNETs are also discussed, comparing the clinical features of adult-onset and pediatric-onset cases that initially present as acute pancreatitis.

Immunophenotypic and molecular characterization of pancreatic neuroendocrine tumors producing serotonin

Serotonin producing pancreatic neuroendocrine tumors (SP-PanNET) account for 0.58-1.4% of all pancreatic neuroendocrine tumors (PanNET). They may present with atypical symptoms, such as acute pancreatitis and are often radiologically characterized by main pancreatic duct dilatation. SP-PanNET are well differentiated neuroendocrine tumors (NET) distinct from classical PanNET by atypical serotonin secretion and abundant dense stroma deposition, like serotonin producing ileal NET leading in some cases to difficulties to reliably distinguish SP-PanNET from ileal NET metastases. The biology and molecular profile of SP-PanNET remain poorly characterized and the cell of origin within the pancreas is unclear. To address these questions, we analyzed a large cohort of SP-PanNET by immunohistochemistry (n = 29; ATRX, DAXX, MENIN, Islet1, PAX6, PDX1, ARX, CDX2), whole genome copy number array (Oncoscan™) and a large NGS panel (NovoPM™) (n = 10), FISH (n = 13) and RNA sequencing (n = 24) together with 21 ileal NET and 29 nonfunctioning PanNET (NF-PanNET). These analyses revealed a unique genomic profile with frequent isolated loss of chromosome 1 (14 cases-61%) and few pathogenic mutations (KMT2C in 2 cases, ARID1A in 1 case). Unsupervised RNAseq-based clustering showed that SP-PanNET were closer to NF-PanNET than ileal NET with an exclusive beta cell-like signature. SP-PanNET showed TGF-β pathway activation signatures associated with extracellular matrix remodeling and similar signature were reproduced in vitro when pancreatic stellate cells were exposed to serotonin. SP-PanNET immunohistochemical profile resemble that of ileal NET except for PDX1 and PAX6 expression to a lesser extend suggesting that these two markers may be useful to diagnose SP-PanNET. Taken together, this suggests that SP-PanNET are a very specific PanNET entity with a peculiar biology leading to the characteristic fibrotic aspect.

New frontiers in imaging including radiomics updates for pancreatic neuroendocrine neoplasms

OBJECTIVE

To illustrate the applications of various imaging tools including conventional MDCT, MRI including DWI, CT & MRI radiomics, FDG & DOTATATE PET-CT for diagnosis, staging, grading, prognostication, treatment planning and assessing treatment response in cases of pancreatic neuroendocrine neoplasms (PNENs).

BACKGROUND

Gastroenteropancreatic neuroendocrine neoplasms (GEP NENs) are very diverse clinically & biologically. Their treatment and prognosis depend on staging and primary site, as well as histological grading, the importance of which is also reflected in the recently updated WHO classification of GEP NENs. Grade 3 poorly differentiated neuroendocrine carcinomas (NECs) are aggressive & nearly always advanced at diagnosis with poor prognosis; whereas Grades-1 and 2 well-differentiated neuroendocrine tumors (NETs) can be quite indolent. Grade 3 well-differentiated NETs represent a new category of neoplasm with an intermediate prognosis. Importantly, the evidence suggest grade heterogeneity can occur within a given tumor and even grade progression can occur over time. Emerging evidence suggests that several non-invasive qualitative and quantitative imaging features on CT, dual-energy CT (DECT), MRI, PET and somatostatin receptor imaging with new tracers, as well as texture analysis, may be useful to grade, prognosticate, and accurately stage primary NENs. Imaging features may also help to inform choice of treatment and follow these neoplasms post-treatment.

CONCLUSION

GEP NENs treatment and prognosis depend on the stage as well as histological grade of the tumor. Traditional ways of imaging evaluation for diagnosis and staging does not yet yield sufficient information to replace operative and histological evaluation. Recognition of important qualitative imaging features together with quantitative features and advanced imaging tools including functional imaging with DWI MRI, DOTATATE PET/CT, texture analysis with radiomics and radiogenomic features appear promising for more accurate staging, tumor risk stratification, guiding management and assessing treatment response.

Pancreatic Neoplasms: CT Evaluation of the Uncommon Presentations of Common Lesions and Common Presentations of the Uncommon Lesions!

Pancreatic masses are commonly encountered entities in radiology practice. Pancreatic ductal adenocarcinomas (PDAC) are the commonest pancreatic malignancies that typically present as infiltrative hypodense focal masses in the pancreatic head, which are hypoattenuating to the pancreatic parenchyma on pancreatic parenchymal and venous phases. However, there are various atypical imaging features of PDACs that create a diagnostic dilemma like tumor in body or tail, diffuse glandular involvement, isoattenuating tumors, cystic changes, or calcifications. Also, few relatively uncommon pancreatic malignancies like pancreatic neuroendocrine tumors, cystic pancreatic tumors, pancreatic lymphoma, and pancreatic metastases present with overlapping features. Accurate radiological characterization of pancreatic masses is important for optimal management and prognostication. Thus, it is imperative for radiologists to be aware of all the uncommon presentations of common pancreatic lesions and common presentations of uncommon pancreatic lesions to avoid erroneous interpretations and establishing the correct diagnosis.

Prediction of recurrence after surgery based on preoperative MRI features in patients with pancreatic neuroendocrine tumors

OBJECTIVES

To investigate useful MRI features in pancreatic neuroendocrine tumor (PNET) patients for predicting recurrence and its timing after surgery.

METHODS

A total of 99 patients with PNET who underwent MRI and surgery from 2000 to 2018 were enrolled. Two radiologists independently assessed MRI findings, including size, location, margin, T1 and T2 signal intensity, enhancement patterns, common bile duct (CBD) or main pancreatic duct (MPD) dilatation, vascular invasion, lymph node enlargement, DWI, and ADC value. Imaging findings associated with recurrence and disease-free survival (DFS) were assessed using logistic regression analysis and Cox proportional hazard regression analysis.

RESULTS

The median follow-up period was 40.4 months, and recurrence after surgery occurred in 12.1% (12/99). Among them, 6 patients experienced recurrence within 1 year, and 9 patients experienced recurrence within 2 years after surgery. In multivariate analysis, major venous invasion (OR 10.76 [1.14-101.85], p = 0.04) was associated with recurrence within 1 year, and portal phase iso- to hypoenhancement (OR 51.89 [1.73-1557.89], p = 0.02), CBD or MPD dilatation (OR 10.49 [1.35-81.64], p = 0.03) and larger size (OR 1.05 [1.00-1.10], p = 0.046) were associated with recurrence within 2 years. The mean DFS was 116.4 ± 18.5 months, and the 5-year DFS rate was 85.7%. In multivariate analysis, portal phase iso- to hypoenhancement (HR 21.36 [2.01-197.77], p = 0.01), ductal dilatation (HR 5.22 [1.46-18.68], p = 0.01), major arterial invasion (HR 42.90 [3.66-502.48], p = 0.003), and larger size (HR 1.04 [1.01-1.06], p = 0.01) showed a significant effect on poor DFS.

CONCLUSION

MRI features, including size, enhancement pattern, vascular invasion, and ductal dilatation, are useful in predicting recurrence and poor DFS after surgery in PNET. Key Points • MRI features are useful for predicting prognosis in patients with PNET after surgery. • PV or SMV invasion (OR 10.49 [1.35-81.64], p = 0.04) was significantly associated with 1-year recurrence. • Portal phase iso- to hypoenhancement (HR 21.36), CBD or MPD dilatation (HR 5.22), arterial invasion (HR 42.90), and larger size (HR 1.04) had significant effects on poor DFS (p < 0.05).

Pancreatic neuroendocrine neoplasms: Clinicopathological features and pathological staging

The nomenclature and classification of pancreatic neuroendocrine neoplasms has evolved in the last 15 years based on the advances in knowledge of the genomics, clinical behaviour and response to therapies. The current 2019 World Health Organization classification of pancreatic neuroendocrine neoplasms categorises them into three groups; pancreatic neuroendocrine tumours (PanNETs)(grade 1 grade 2, grade 3), pancreatic neuroendocrine carcinomas and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) based on the mitotic rate, Ki-67 index, morphological differentiation and/or co-existing tissue subtype. PanNETs are also classified into non-functional NET, insulinoma, gastrinoma, VIPoma, glucagonoma, somatostatinoma, ACTH-producing NET and serotonin producing NET based on hormone production and clinical manifestations. A portion of the cases were associated with genetic syndromes such as multiple neuroendocrine neoplasia 1 (MEN 1), neurofibromatosis and Von Hippel-Lindau syndrome. In view of the distinctive pathology and clinical behaviour of PanNENs, the current 8th AJCC/UICC staging system has separated prognostic staging grouping for PanNETs from the pancreatic neuroendocrine carcinomas or MiNENs. Pancreatic neuroendocrine carcinomas and MiNENs are staged according to the prognostic stage grouping for exocrine pancreatic carcinoma. The new stage grouping of PanNETs was validated to have survival curves separated between different prognostic groups. This refined histological and staging would lead to appropriate selections of treatment strategies for the patients with pancreatic neuroendocrine neoplasms.

Role of Endoscopic Ultrasound in the Diagnosis of Pancreatic Neuroendocrine Neoplasms

Although pancreatic neuroendocrine neoplasms (PNENs) are relatively rare tumors, their number is increasing with advances in diagnostic imaging modalities. Even small lesions that are difficult to detect using computed tomography or magnetic resonance imaging can now be detected with endoscopic ultrasound (EUS). Contrast-enhanced EUS is useful, and not only diagnosis but also malignancy detection has become possible by evaluating the vascularity of tumors. Pathological diagnosis using EUS with fine-needle aspiration (EUS-FNA) is useful when diagnostic imaging is difficult. EUS-FNA can also be used to evaluate the grade of malignancy. Pooling the data of the studies that compared the PNENs grading between EUS-FNA samples and surgical specimens showed a concordance rate of 77.5% (κ-statistic = 0.65, 95% confidence interval = 0.59–0.71, p < 0.01). Stratified analysis for small tumor size (2 cm) showed that the concordance rate was 84.5% and the kappa correlation index was 0.59 (95% confidence interval = 0.43–0.74, p < 0.01). The evolution of ultrasound imaging technologies such as contrast-enhanced and elastography and the artificial intelligence that analyzes them, the evolution of needles, and genetic analysis, will further develop the diagnosis and treatment of PNENs in the future.

Intratumoral Fibrosis and Tumor Growth Pattern as Prognostic Factors in Optimally Resected Pancreatic Neuroendocrine Neoplasms: An Analysis of 168 Cases

OBJECTIVES

Pancreatic neuroendocrine neoplasms (PanNENs) can recur after curative resection. We sought to establish the significance of tumor fibrosis and tumor growth pattern as predictors of recurrence-free survival and overall survival.

METHODS

A retrospective query of an institutional surgical database was performed from 2000 to 2018 to identify optimally resected PanNENs. All eligible slides were reviewed by an experienced gastrointestinal pathologist for established histopathologic prognostic factors, as well as fibrosis and tumor growth pattern. We evaluated the effect of the interested variables through Cox proportional hazards models.

RESULTS

One hundred sixty-eight cases were considered. The majority of patients (90%) had grade 1 or 2 tumors, 46% showed significant fibrosis, and 22% demonstrated an infiltrative growth pattern. Twenty-one percent of patients had a recurrence. In multivariable analysis, lymphovascular invasion with a hazard ratio (HR) of 5.1 and infiltrative growth pattern (HR, 2.8) were significantly associated with increased risk of recurrence and increased risk of death (HR, 3.6 and 2.7, respectively). There was a significant decrease in recurrence-free survival and overall survival for fibrosis and infiltrative growth pattern.

CONCLUSIONS

In optimally resected PanNENs, the presence of fibrosis and infiltrative growth pattern are significant risk factors for recurrence and/or decreased survival.

Differentiating pancreatic neuroendocrine tumors from pancreatic ductal adenocarcinomas by the "Duct-Road Sign": A preliminary magnetic resonance imaging study

To assess the duct-road sign and tumor-to-duct ratio (TDR) in MRI for differentiating pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal-adenocarcinomas (PDACs).Retrospectively reviewed MRI characteristics of 78 pancreatic masses (histopathology-proven 25 PNETs and 53 PDACs). Receiver operating characteristics with TDR and diagnostic performance of the duct-road sign for differential diagnosis were performed.The prevalence of duct-road sign in PNETs was higher than that for PDACs (84% vs 0%; P < .001). A strong correlation (r = 0.884, P < .001) was observed between MRI for PNETs and the frequency of this sign. Performance characteristics of the duct-road sign in MRI for PNET diagnosis were sensitivity (84%, [21 of 25]), specificity (100%, [53 of 53]), positive predictive value (100%, [21 of 21]), negative predictive value (92.9%, [53 of 57]), and accuracy (94.8%, [74 of 78]). In the intention-to-diagnose analysis, the corresponding values were 67.7% (21 of 31), 100% (53 of 53), 100% (21 of 21), 84.1% (53 of 63), and 88.1% (74 of 84). The TDR in PNETs was observed to be greater than that in PDACs (14.6 ± 9.3 vs 6.9 ± 3.8, P = .001). TDR with a cut-off value of 7.7 had high sensitivity (84%) and specificity (66%) with area under curve (0.802, 95% CI: 0.699, 0.904; P < .001) for distinguishing PNETs from PDACs.The presence of duct-road sign and TDR > 7.7 on MRI may assist in diagnosis for PNET instead of PDAC.

Differentiation of pancreatic neuroendocrine tumors from pancreas renal cell carcinoma metastases on CT using qualitative and quantitative features

PURPOSE

To assess qualitative and quantitative imaging features on enhanced CT that may differentiate pancreatic neuroendocrine tumors (PNETs) from pancreatic renal cell carcinoma (RCC) metastases.

METHODS

This IRB-approved multi-center retrospective case-control study compared 43 resected PNETs and 28 resected RCC metastases with pre-operative enhanced CT identified consecutively between 2003 and 2017. Two blinded radiologists (R1/R2) independently assessed tumor location, attenuation (relative to pancreas), composition (solid/cystic/mixed), homogeneity (homogeneous/heterogeneous), calcification, multiplicity, and for main pancreatic duct (MPD) dilation. Tumors were segmented for quantitative texture analysis. Data were analyzed with Chi square, logistic regression, and receiver operating characteristic (ROC). Inter-observer agreement was assessed (Cohen's kappa).

RESULTS

There was no difference in age, gender, location, attenuation, or composition (P > 0.05) between groups. PNETs were larger than RCC metastases (37 ± 23 mm vs. 26 ± 21 mm, P = 0.038), more frequently solitary (P < 0.001), subjectively more heterogeneous (P = 0.033/0.144, R1/R2), and associated with calcification (P = 0.002/0.004) and MPD dilation (P = 0.025/0.006). Agreement for subjective features was moderate-to-almost perfect (K = 0.4879-0.9481). Quantitative texture analysis showed higher entropy in PNETs (6.32 ± 0.49 versus 5.96 ± 0.53; P = 0.004) with no difference in other features studied (P > 0.05). Entropy had ROC area under the curve for diagnosis of PNET of 0.77 ± 0.06, with optimal sensitivity/specificity of 71.4/79.1%.

CONCLUSIONS

Compared to pancreatic RCC metastases, PNETs are larger, more frequently solitary, contain calcification, show MPD dilation, and are subjectively and quantitatively more heterogeneous tumors.

[Pancreatic Neuroendocrine Tumor Presenting as Acute Pancreatitis]

We report a case of acute pancreatitis secondary to pancreatic neuroendocrine tumor. A 46-year old man presented with upper abdominal pain. The serum amylase and lipase were elevated. Abdominal computed tomography (CT) and magnetic resonance cholangiopancreatography revealed a 1.7 cm sized mass at the pancreas body with a dilatation of the upstream pancreatic duct and mild infiltrations of peripancreatic fat. An endoscopic ultrasound-guided fine needle biopsy was performed for the pancreatic mass, but only necrotic tissue was observed on the pathologic examination. A chest and neck CT scan revealed anterior mediastinal, paratracheal, and cervical lymph node enlargement, which were indicative of metastasis. An ultrasound-guided core needle biopsy was performed for the enlarged neck lymph node, and pathologic examination revealed a metastatic poorly differentiated carcinoma. Immunohistochemical analysis showed positive staining for synaptophysin, chromogranin A, and CD 56, indicative of a neuroendocrine carcinoma.

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.

Endoscopic ultrasound appearance of pancreatic serotonin-staining neuroendocrine neoplasms

BACKGROUND/OBJECTIVES

The pancreatic localization of serotonin-staining neuroendocrine neoplasms is extremely rare. This is a retrospective study aimed at analyzing the endoscopic ultrasound appearance of pancreatic serotoninoma.

METHODS

Between 2010 and 2016, all consecutive patients with histologically proven pancreatic serotoninoma who had undergone endoscopic ultrasound were enrolled.

RESULTS

Eight patients (six F, median age 68.5 years) had a diagnosis of pancreatic serotoninoma and underwent endoscopic ultrasound examinations. Median diameter of the lesion was ten mm. The nodule echotexture was hypoechoic in seven out of eight cases. The most frequent localization was the pancreatic neck (four); in three cases, the tumor was located in the pancreatic head and in one in the body. In seven cases the tumor caused a main pancreatic duct dilation; in three cases also the secondary ducts were dilated. In one case a dilation of the common bile duct was observed. At contrast-enhanced endoscopic ultrasound no one showed the typical contrast-enhancement. Elastography (available in two patients) showed a rigid pattern of the lesion.

CONCLUSIONS

From this case series a specific endoscopic ultrasound appearance resulted for pancreatic serotoninoma, different from other types of pancreatic neuroendocrine neoplasm, but it is difficult to differentiate it from a pancreatic adenocarcinoma or an intraductal papillary mucinous neoplasm.

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.

Pancreatic carcinoids (serotonin-producing pancreatic neuroendocrine neoplasms): Report of 5 cases and review of the literature

INTRODUCTION

Pancreatic neuroendocrine neoplasms (pNENs) are relatively rare tumors representing 1% to 2% of all pancreatic neoplasms. These tumors can secrete a variety of biologically active substances giving rise to distinct clinical symptoms or can be clinically nonfunctioning. Apart from insulinomas and gastrinomas, which constitute the majority of functioning pNENs, some tumors may secrete serotonin presenting with the features of the carcinoid syndrome. These so-called pancreatic carcinoids are considered relatively rare tumors and are associated with increased urinary levels of 5-hydroxyindoleacetic acid (5-HIAA). It has recently been suggested that the prevalence of such tumors might be underestimated.

CASES

We present a series of 5 patients from our database of 138 pNENs (5/138, 3.62%), harboring serotonin-producing pNENs and describe their distinctive clinical, biochemical, histopathological features, and response to treatment along with a review of the relevant available literature.

CONCLUSION

Such tumors are considered rare, although this may be an underestimate as systematic screening for the presence of serotonin in tissue or elevated urinary 5-HIAA levels in patients with apparently nonfunctioning pNENs is not currently recommended. In order to reach such a consensus, data from large prospective studies are needed in order to evaluate the impact of this type of tumors in survival and clinical outcome, since some studies have suggested a worse prognosis.

Post-obstructive cyst formation in pancreas and cystic acinar transformation: Are they same?

Pancreatic "acinar cell cystadenoma" (PACA) is a rare benign pancreatic cystic lesion showing acinar cell differentiation. The neoplastic nature of PACA has been questioned and its exact pathogenesis remains unclear. To investigate that acinar cell differentiation is a non-specific metaplastic phenomenon that can occur in pancreatic ductal system, especially when chronically inflamed and dilated, and doesn't necessarily imply an acinar cell neoplasm, we retrospectively analyzed cases diagnosed as PACA and cases with post-obstructive cystic dilatation of pancreatic ducts for acinar cell differentiation using immunohistochemistry for trypsin. The etiology of obstruction was microscopic periductal pancreatic neuroendocrine tumors (PanNET) and pancreatic ductal adenocarcinomas (PDAC). All cases of post-obstructive cystic dilatation showed multiple varying sized cysts distal to the obstruction with histologic findings virtually identical to PACAs. The cysts in both conditions were lined by a single layer of non-dysplastic flattened to columnar ductal-type epithelium with areas of acinar cell differentiation. Trypsin immunohistochemistry confirmed presence of acinar cell differentiation in all cases of post-obstructive cysts and PACAs. Our results suggest that acinar cell differentiation is common in post-obstructive cyst formation, and changes are identical to PACAs. These findings further support the notion that PACA is a benign non-neoplastic cystic lesion with acinar cell differentiation. The findings also suggest that in cases with histology resembling "PACA" or showing diffuse ductal cystic dilation, careful gross examination should be carried out for a proximal obstructive lesion, which can be subtle and easily be missed on initial examination.

National Rise of Primary Pancreatic Carcinoid Tumors: Comparison to Functional and Nonfunctional Pancreatic Neuroendocrine Tumors

BACKGROUND

New guidelines recommend differentiating between carcinoid and pancreatic neuroendocrine tumors (PNETs) during clinical trials. However, little is known about the behavior and incidence of primary pancreatic carcinoid tumors.

STUDY DESIGN

We performed a retrospective cohort study using the National Cancer Data Base (NCDB) to identify adults with primary PNETs diagnosed between 2004 and 2013. The Kaplan-Meier method was used to evaluate overall survival, and multivariate Cox proportional hazards model was used to assess the hazard of death in resected patients.

RESULTS

Of 10,752 patients, 12.7% were diagnosed with carcinoid tumors, 84.7% with nonfunctional and 2.6% with functional PNETs. Although the number of functional PNETs has remained relatively constant over time, rates of nonfunctional and carcinoid tumors have risen dramatically. Only 36 (5.7%) carcinoid tumors were diagnosed in 2004; this increased to 497 (27.7%) in 2013. Overall survival was significantly longer for carcinoid compared with functional and nonfunctional tumors (log-rank p < 0.0001), with 5-year survival rates of 63.1%, 58.3%, and 52.6%, respectively. For patients having resection, overall survival further improved for carcinoid tumors relative to functional (log-rank p = 0.0011) and nonfunctional (log-rank p < 0.0001) tumors, but the survival difference between functional and nonfunctional tumors disappeared (log-rank p = 0.4579); 5-year survival rates were 89.2%, 76.6%, and 78.7%, respectively. On multivariate Cox regression of the resected cohort, mortality was significantly higher for patients with functional (hazard ratio [HR] 1.81) and nonfunctional (HR 1.40) PNETs compared with carcinoid tumors.

CONCLUSIONS

Primary pancreatic carcinoid tumors are increasingly being diagnosed. Differentiating PNET subtypes plays an important role in prognostication. Resection remains a critical component of care.

Neuroendocrine carcinoma of the pancreas with similar genetic alterations to invasive ductal adenocarcinoma

Neuroendocrine carcinoma (NEC) of the pancreas is very rare, and its origin is not fully elucidated. Here, we present a case of a small-size NEC of the pancreas that is genetically similar to invasive ductal adenocarcinoma (IDA). A 65-year-old man was referred to our hospital due to obstructive jaundice and found to have a 12-mm solid tumor in the pancreas head. The tumor exhibited low vascularity on enhanced computed tomography, and endoscopic retrograde pancreatographic imaging revealed an irregular obstruction in a branch duct of the pancreas. The patient was thereby diagnosed with a pancreatic ductal cancer, and stomach-preserving pancreaticoduodenectomy with regional lymph node resection was performed. Histochemical analysis of the resected tumor showed that the neoplastic cells with scanty cytoplasm and hyperchromatic nuclei strongly expressed chromogranin A and synaptophysin. The Ki-67 index was 40 % in the most proliferative tumor regions, and the tumor was diagnosed as a NEC of the pancreas. However, in the analysis of genetic alterations of the tumor tissue, the neoplastic cells showed altered KRAS, TP53, and SMAD4/DPC4, suggesting that the NEC in our case is genetically related to IDA. Our data suggest that poorly differentiated IDAs may transform into NECs.

Uncommon presentations of common pancreatic neoplasms: a pictorial essay

Pancreatic neoplasms are a wide group of solid and cystic lesions with different and often characteristic imaging features, clinical presentations, and management. Among solid tumors, ductal adenocarcinoma is the most common: it arises from exocrine pancreas, comprises about 90% of all pancreatic neoplasms, and generally has a bad prognosis; its therapeutic management must be multidisciplinary, involving surgeons, oncologists, gastroenterologists, radiologists, and radiotherapists. The second most common solid pancreatic neoplasms are neuroendocrine tumors: they can be divided into functioning or non-functioning and present different degrees of malignancy. Cystic pancreatic neoplasms comprise serous neoplasms, which are almost always benign, mucinous cystic neoplasms and intraductal papillary mucinous neoplasms, which can vary from benign to frankly malignant lesions, and solid pseudopapillary tumors. Other pancreatic neoplasms, such as lymphoma, metastases, or pancreatoblastoma, are rarely seen in clinical practice and have different and sometimes controversial managements. Rare clinical presentations and imaging appearance of the most common pancreatic neoplasms, both solid and cystic, are more frequently seen and clinically relevant than rare pancreatic tumors; their pathologic and radiologic appearances must be known to improve their management. The purpose of this paper is to present some rare or uncommon clinical and radiological presentations of common pancreatic neoplasms providing examples of multi-modality imaging approach with pathologic correlations, thus describing the histopathological bases that can explain the peculiar imaging features, in order to avoid relevant misdiagnosis and to improve lesion management.

Pathologic Evaluation and Reporting of Intraductal Papillary Mucinous Neoplasms of the Pancreas and Other Tumoral Intraepithelial Neoplasms of Pancreatobiliary Tract: Recommendations of Verona Consensus Meeting

BACKGROUND

There are no established guidelines for pathologic diagnosis/reporting of intraductal papillary mucinous neoplasms (IPMNs).

DESIGN

An international multidisciplinary group, brought together by the Verona Pancreas Group in Italy-2013, was tasked to devise recommendations.

RESULTS

(1) Crucial to rule out invasive carcinoma with extensive (if not complete) sampling. (2) Invasive component is to be documented in a full synoptic report including its size, type, grade, and stage. (3) The term "minimally invasive" should be avoided; instead, invasion size with stage and substaging of T1 (1a, b, c; ≤ 0.5, > 0.5-≤ 1, > 1 cm) is to be documented. (4) Largest diameter of the invasion, not the distance from the nearest duct, is to be used. (5) A category of "indeterminate/(suspicious) for invasion" is acceptable for rare cases. (6) The term "malignant" IPMN should be avoided. (7) The highest grade of dysplasia in the non-invasive component is to be documented separately. (8) Lesion size is to be correlated with imaging findings in cysts with rupture. (9) The main duct diameter and, if possible, its involvement are to be documented; however, it is not required to provide main versus branch duct classification in the resected tumor. (10) Subtyping as gastric/intestinal/pancreatobiliary/oncocytic/mixed is of value. (11) Frozen section is to be performed highly selectively, with appreciation of its shortcomings. (12) These principles also apply to other similar tumoral intraepithelial neoplasms (mucinous cystic neoplasms, intra-ampullary, and intra-biliary/cholecystic).

CONCLUSIONS

These recommendations will ensure proper communication of salient tumor characteristics to the management teams, accurate comparison of data between analyses, and development of more effective management algorithms.

Expression of CD24, a Stem Cell Marker, in Pancreatic and Small Intestinal Neuroendocrine Tumors

OBJECTIVES

CD24 has been considered a normal and cancer stem cell marker. Potential intestinal stem cells weakly express CD24. In the pancreas, CD24 is a possible cancer stem cell marker for ductal adenocarcinoma.

METHODS

Expression of CD24 in intestinal and pancreatic neuroendocrine tumors (NETs) was examined. Immunohistochemistry was performed on benign duodenum, ileum mucosa, and pancreas, as well as primary duodenal, primary and metastatic ileal, and pancreatic NETs.

RESULTS

Scattered CD24-positive cells were noted in the duodenal and ileal crypts, most of which showed a strong subnuclear labeling pattern. Similar expression was observed in 41 (95%) of 43 primary ileal NETs but in only four (15%) of 26 duodenal NETs (P < .01). In addition, metastatic ileal NETs retained CD24 expression. Pancreatic islets did not express CD24, and only rare cells had subnuclear labeling of CD24 in the pancreatic ducts. Unlike ileal NETs, only five (5%) of 92 pancreatic NETs expressed CD24 in the subnuclear compartment (P < .01). All five NETs showed a unique morphology with prominent stromal fibrosis.

CONCLUSIONS

CD24 expression was frequent in primary and metastatic midgut NETs but rare in pancreatic and duodenal NETs. Expression of CD24 in ileal NETs may have future diagnostic and therapeutic implications.

Cadherin 17 is frequently expressed by 'sclerosing variant' pancreatic neuroendocrine tumour

AIMS

Recently, we described a series of pancreatic neuroendocrine tumours (PanNETs) featuring prominent stromal fibrosis, which we called sclerosing PanNETs. The aim of this study was to examine the pathological, immunophenotypic and clinical differences between sclerosing and non-sclerosing PanNETs.

METHODS AND RESULTS

One hundred and six PanNETs were identified, of which 15 (14%) were sclerosing NETs. Tissue microarrays containing 44 non-sclerosing and five sclerosing PanNETs, as well as sections from 10 additional sclerosing tumours, were immunohistochemically labelled for serotonin, CDX2, CDH17, and islet 1. Sclerosing PanNETs were smaller (P = 0.045) and more likely to show an infiltrative growth pattern (P < 0.001) than non-sclerosing PanNETs. They were frequently associated with a large pancreatic duct, causing duct stenosis. Additionally, we found significantly increased expression of the small intestinal NET markers serotonin, CDX2 and CDH17 in sclerosing PanNETs (P < 0.001) as compared with non-sclerosing PanNETs. No difference in clinical outcome was found; however, more sclerosing PanNETs were stage IIB or above (P = 0.035), with lymph node metastasis being seen in three of nine sclerosing PanNETs with a tumour size of <20 mm.

CONCLUSIONS

Sclerosing PanNETs have distinct pathological features and biomarker expression profiles. In addition, lymph node metastasis can be present even with small sclerosing PanNETs.

Pancreatic neuroendocrine tumors: pathologic and molecular characteristics

Pancreatic neuroendocrine neoplasms include mainly well-differentiated neuroendocrine tumors but also rare poorly differentiated neuroendocrine carcinomas. Molecular mechanisms underlying pancreatic neuroendocrine tumorigenesis have recently been elucidated. While alterations in the chromatin remodeling and PI3K/Akt/mTOR pathways are present in most well-differentiated pancreatic neuroendocrine tumors, mutations in TP53 and RB may contribute to the development of pancreatic poorly differentiated neuroendocrine carcinomas. With these discoveries, new molecular targeted therapies have become available and show promise in some patients with pancreatic well-differentiated neuroendocrine tumor.

Primary solid pancreatic tumors: recent imaging findings updates with pathology correlation

The imaging findings of primary solid pancreatic tumors have long been studied and are generally well-established. However, interestingly enough, a wealth of new information has recently appeared in the literature, including the imaging findings of novel or previously seldom-addressed pathological entities as well as atypical imaging findings of common tumors, both of which are well-correlated with the pathology findings. 5 %-14 % of pancreatic ductal adenocarcinomas have been reported on dynamic contrast-enhanced computed tomography to be isoattenuating, and thus making the imaging diagnosis challenging. The imaging-pathology correlation in such isoattenuating tumors is presented along with a discussion regarding the early imaging detection of pancreatic cancers. Colloid (or mucinous non-cystic) pancreatic cancer may resemble a less harmful cystic lesion due to its abundant extracellular mucin, and thus requiring caution in the image interpretation. Serotonin-producing neuroendocrine tumors have recently been recognized as a separate entity from usual neuroendocrine tumors. Exuberant fibrosis caused by serotonin metabolites and scarce tumor cells creates a unique pattern of pancreatic ductal obstruction seen on imaging. Small solid pseudopapillary tumors appear as unencapsulated, completely solid lesions with gradually increasing enhancement after contrast administration, unlike typical solid pseudopapillary neoplasms that present as a large mixed solid and degenerated cystic or hemorrhagic mass encapsulated by a thick capsule and which, therefore, tend to be misdiagnosed on imaging. Solid serous adenoma is a rare, solid variant of serous cystadenoma and appears on imaging as a hypervascular, solid nodule due to its genuinely microscopic cystic, alveolar, and ectatic tubular tumor architecture.

Whipple made simple for surgical pathologists: orientation, dissection, and sampling of pancreaticoduodenectomy specimens for a more practical and accurate evaluation of pancreatic, distal common bile duct, and ampullary tumors

Pancreaticoduodenectomy (PD) specimens present a challenge for surgical pathologists because of the relative rarity of these specimens, combined with the anatomic complexity. Here, we describe our experience on the orientation, dissection, and sampling of PD specimens for a more practical and accurate evaluation of pancreatic, distal common bile duct (CBD), and ampullary tumors. For orientation of PDs, identification of the "trapezoid," created by the vascular bed at the center, the pancreatic neck margin on the left, and the uncinate margin on the right, is of outmost importance in finding all the pertinent margins of the specimen including the CBD, which is located at the upper right edge of this trapezoid. After orientation, all the margins can be sampled. We submit the uncinate margin entirely as a perpendicular inked margin because this adipose tissue-rich area often reveals subtle satellite carcinomas that are grossly invisible, and, with this approach, the number of R1 resections has doubled in our experience. Then, to ensure proper identification of all lymph nodes (LNs), we utilize the orange-peeling approach, in which the soft tissue surrounding the pancreatic head is shaved off in 7 arbitrarily defined regions, which also serve as shaved samples of the so-called "peripancreatic soft tissue" that defines pT3 in the current American Joint Committee on Cancer TNM. With this approach, our LN count increased from 6 to 14 and LN positivity rate from 50% to 73%. In addition, in 90% of pancreatic ductal adenocarcinomas there are grossly undetected microfoci of carcinoma. For determination of the primary site and the extent of the tumor, we believe bisectioning of the pancreatic head, instead of axial (transverse) slicing, is the most revealing approach. In addition, documentation of the findings in the duodenal surface of the ampulla is crucial for ampullary carcinomas and their recent site-specific categorization into 4 categories. Therefore, we probe both the CBD and the pancreatic duct from distal to the ampulla and cut the pancreatic head to the ampulla at a plane that goes through both ducts. Then, we sample the bisected pancreatic head depending on the findings of the case. For example, for proper staging of ampullary carcinomas, it is imperative to take the sections perpendicular to the duodenal serosa at the "groove" area, as ampullary carcinomas often extend to this region. Amputative (axial) sectioning of the ampulla, although good for documentation of the peri-Oddi spread of the intra-ampullary tumors, unfortunately disallows documentation of mucosal spread of the papilla of Vater tumors (those arising from the edge of the ampulla, where the ducts transition to duodenal mucosa and extending) into the neighboring duodenum. Axial sectioning also often fails to document tumor spread to the "groove" area. In conclusion, knowledge of the gross characteristics of the anatomic hallmarks is essential for proper dissection of PD specimens. The approach described above allows practical and accurate documentation and staging of pancreas, distal CBD, and ampullary cancers.

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.

Pancreatic imaging mimics: part 1, imaging mimics of pancreatic adenocarcinoma

OBJECTIVE

The purpose of this article is to describe the imaging features of diseases that may closely simulate pancreatic adenocarcinoma, either radiologically or pathologically.

CONCLUSION

Neoplastic and inflammatory diseases that can closely simulate pancreatic adenocarcinoma include neuroendocrine tumor, metastasis to the pancreas, lymphoma, groove pancreatitis, autoimmune pancreatitis, and focal chronic pancreatitis. Atypical imaging findings that should suggest diagnoses other than adenocarcinoma include the absence of significant duct dilatation, incidental detection, hypervascularity, large size (> 5 cm), IV tumor thrombus, and intralesional ducts or cysts.

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.

Serotonin expression in pancreatic neuroendocrine tumors correlates with a trabecular histologic pattern and large duct involvement

Pancreatic neuroendocrine tumors with prominent stromal fibrosis are often clinically, radiographically, and grossly indistinguishable from ductal adenocarcinoma. We recently described a small series of fibrotic pancreatic neuroendocrine tumors that express serotonin. To understand better the relationship between histopathologic patterns and serotonin expression, we reviewed 361 pancreatic neuroendocrine tumors to identify those with prominent stromal fibrosis exceeding 30% of total tumor area. We identified 52 cases and immunolabeled these neoplasms with antibodies to serotonin and Ki-67. Two predominant histologic subtypes were identified: 14 (26.9%) of 52 had a trabecular or trabecular-glandular cellular pattern with interspersed fibrosis, whereas 38 (73.1%) of 52 had solid architecture. Of the 52, 14 (26.9%) pancreatic neuroendocrine tumors showed at least focal serotonin immunoreactivity. Tumors with predominantly trabecular architecture were significantly more likely to express serotonin than those with solid architecture (P < .01). Only 2 of 34 pancreatic neuroendocrine tumors with fibrosis less than 30% of total tumor area expressed serotonin. The 14 serotonin-expressing tumors were less likely to have lymph node metastases (P = .016) and more likely to involve large pancreatic ducts (P < .01) than were the 38 serotonin-negative tumors. The serotonin-expressing tumors were also found in a younger patient population (P < .01). There was no significant association of serotonin immunoreactivity with Ki-67 proliferation index, tumor size, or distant metastases. Our data demonstrate a strong correlation between trabecular architecture and serotonin immunoreactivity in pancreatic neuroendocrine tumors with stromal fibrosis. Serotonin-expressing tumors are also less likely to have lymph node metastases and more likely to involve large pancreatic ducts.