Contrasting clinical manifestations of SDHB and VHL associated chromaffin tumours

Retroperitoneal paraganglioma with loss of heterozygosity of the von Hippel-Lindau gene: a case report and review of the literature

Von Hippel-Lindau (VHL) disease is an autosomal dominant disease related to germline mutations in VHL. In VHL disease, pheochromocytoma develops in 10%-20% of patients because of germline mutations and loss of heterozygosity of VHL. However, the rate of paraganglioma associated with VHL is low compared with that of pheochromocytoma, and the reason is unknown. In this study, we performed germline and somatic mutation analyses of retroperitoneal paraganglioma that developed in a patient with clinically diagnosed VHL disease and investigated the tumorigenic mechanism of paraganglioma. The patient was a 25-year-old woman who was considered to have VHL disease on the basis of her family history. She was referred to our clinic to investigate a tumor at the bifurcation of the common iliac artery. The tumor was diagnosed as retroperitoneal paraganglioma by clinical evaluations. A left renal cell carcinoma was also suspected. Polymerase chain reaction direct sequencing analysis and polymorphic microsatellite analysis within the VHL locus suggested that loss of heterozygosity of VHL was associated with paraganglioma and renal cell carcinoma. Multiplex ligation-dependent probe amplification analysis showed a loss of the copy number of VHL exons in paraganglioma. These results suggest that VHL disease contributes to the development of paraganglioma. A literature review showed no reported common missense variants involved in the progression of paraganglioma. The loss of heterozygosity of VHL can be a tumorigenic mechanism of retroperitoneal paraganglioma in VHL disease. However, the low rate of paraganglioma compared with pheochromocytoma is not explained by their genetic background alone.

Functional Imaging of Paragangliomas with an Emphasis on Von Hippel-Lindau-Associated Disease: A Mini Review

Few reports have presented data and results on functional (i.e., nuclear medicine) imaging of paragangliomas and pheochromocytomas (PGLs/PHEOs) for von Hippel-Lindau (VHL) patients. Nuclear medicine localization modalities for chromaffin tumors can be specific or nonspecific. Specific methods make use of the expression of the human norepinephrine transporter (hNET) and vesicular monoamine transporters (VMATs) by these tumors. These permit the use of radiolabeled ligands that enter the synthesis and storage pathway of catecholamines. Nonspecific methods are not related to the synthesis, uptake, or storage of catecholamines but make use of the tumors' high glucose metabolism or expression of somatostatin receptors. Consensuses and guidelines suggest that metastatic and sporadic PHEOs/PGLs in VHL patients (as in patients with chromaffin tumors of yet unknown genotype) should be evaluated first with ¹⁸F-dihydroxyphenylalanine (¹⁸F-DOPA) positron emission tomography/computed tomography (PET/CT). The functional imaging of second choice is ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) for PHEOs in VHL patients. ¹²³I-MIBG, ⁶⁸Ga-DOTATATE/DOTATOC/DOTANOC PET/CT, or ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT can be a second choice of functional imaging for PGLs in VHL patients.

Detection and management of retroperitoneal cystic lesions: A case report and review of the literature

The identification of cystic lesions within the retroperitoneal space is a rare event that poses clinicians the challenge of a difficult diagnosis and disease management. Retroperitoneal cystic lesions account for a group of lesions that range from common benign lesions (e.g., lymphoceles developing as a surgical complication) to rare aggressive malignant neoplasms. Currently, in the majority of cases, image-guided procedures allow for a pathological diagnosis to be achieved in these challenging lesions, thus offering the chance of an appropriate treatment; however, the overall clinical assessment of retroperitoneal cysts is highly demanding. The present study reports the management of a representative clinical case, presenting with a voluminous cystic mass able to dislocate cave vein, whose diagnosis was preceded by a deep vein thrombosis. Computed tomography-scan and ultrasound guided percutaneous drainage were performed to achieve the diagnosis. Following the discussion of the current case report, a review of the pathological and radiological characteristics of retroperitoneal cystic lesions is presented.

Outcomes of annual surveillance imaging in an adult and paediatric cohort of succinate dehydrogenase B mutation carriers

OBJECTIVE

For 'asymptomatic carriers' of the succinate dehydrogenase subunit B (SDHB) gene mutations, there is currently no consensus as to the appropriate modality or frequency of surveillance imaging. We present the results of a surveillance programme of SDHB mutation carriers.

DESIGN

Review of clinical outcomes of a surveillance regimen in patients identified to have an SDHB gene mutation, based on annual MRI, in a single UK tertiary referral centre.

PATIENTS

A total of 92 patients were identified with an SDHB gene mutation. a total of 27 index patients presented with symptoms, and 65 patients were identified as asymptomatic carriers.

MEASUREMENTS

Annual MRI of the abdomen, with alternate year MRI of the neck, thorax and pelvis. Presence of an SDHB-related tumour included paraganglioma (PGL), phaeochromocytoma (PCC), renal cell carcinoma (RCC) and gastrointestinal stromal tumour (GIST).

RESULTS

A total of 43 PGLs, eight PCCs and one RCC occurred in the 27 index patients (23 solitary, four synchronous, five metachronous). A further 15 SDHB-related tumours (11 PGLs, three RCCs, one GIST) were identified in the asymptomatic carriers on surveillance screening (25% of screened carriers): 10 on the first surveillance imaging and five on subsequent imaging 2-6 years later. A total of 11 patients had malignant disease.

CONCLUSIONS

SDHB-related tumours are picked up as early as 2 years after initial negative surveillance scan. We believe the high malignancy rate and early identification rate of tumours justifies the use of 1-2 yearly imaging protocols and MRI-based imaging could form the mainstay of surveillance in this patient group thereby minimizing radiation exposure.

Somatic and germline mutations in NETs: Implications for their diagnosis and management

It is now understood that specific somatic and germline mutations may lead to the development of the neuroendocrine tumours (NETs). NETs usually occur as sporadic isolated tumours, although they also may present as part of complex familial endocrine cancer syndromes, such as multiple endocrine neoplasia type 1 (MEN1) and type 2 (MEN2), Von Hippel-Lindau (VHL) and neurofibromatosis syndromes, tuberous sclerosis, Carney triad and dyad, Reed syndrome and polycythaemia-paraganglioma syndromes. Only in MEN2 syndrome is there a specific genotype-phenotype correlation, although in both sporadic and syndromic NETs some gene mutations are associated with specific clinico-pathological features and prognosis. There have been several advances in our understanding of the NETs leading to earlier detection and targeted therapeutic treatment, but given the poor prognosis associated with metastatic NETs, it will be necessary to find new biomarkers for the prediction of malignant potential and to find novel therapeutic targets for NETs.

Endocrine manifestations of von Hippel-Lindau disease

von Hippel-Lindau (VHL) disease is an autosomal dominant disorder caused by heterozygous mutations in the VHL tumor suppressor gene that is characterized by the occurrence of multiple endocrine and nonendocrine lesions. This review focuses on the endocrine manifestations of VHL disease. Pancreatic neuroendocrine proliferations (ductuloinsular complexes, islet dysplasia, endocrine microadenoma, and neuroendocrine tumors), pheochromocytomas, and extra-adrenal paragangliomas are important endocrine manifestations of VHL disease. They frequently display characteristic clinical, biochemical, and histopathologic features that, although not pathognomonic, can be helpful in suggesting VHL disease as the underlying etiology and distinguishing these tumors from sporadic cases. Recent improvements in treatment and outcomes of renal cell carcinomas have allowed pancreatic neuroendocrine tumors to emerge as a significant source of metastatic disease, making the accurate recognition and classification of these neoplasms by the pathologist of utmost importance to determine prognosis, treatment, and follow-up strategies for affected patients.

Succinate dehydrogenase (SDH)-deficient renal carcinoma: a morphologically distinct entity: a clinicopathologic series of 36 tumors from 27 patients

Succinate dehydrogenase (SDH)-deficient renal carcinoma has been accepted as a provisional entity in the 2013 International Society of Urological Pathology Vancouver Classification. To further define its morphologic and clinical features, we studied a multi-institutional cohort of 36 SDH-deficient renal carcinomas from 27 patients, including 21 previously unreported cases. We estimate that 0.05% to 0.2% of all renal carcinomas are SDH deficient. Mean patient age at presentation was 37 years (range, 14 to 76 y), with a slight male predominance (M:F=1.7:1). Bilateral tumors were observed in 26% of patients. Thirty-four (94%) tumors demonstrated the previously reported morphology at least focally, which included: solid or focally cystic growth, uniform cytology with eosinophilic flocculent cytoplasm, intracytoplasmic vacuolations and inclusions, and round to oval low-grade nuclei. All 17 patients who underwent genetic testing for mutation in the SDH subunits demonstrated germline mutations (16 in SDHB and 1 in SDHC). Nine of 27 (33%) patients developed metastatic disease, 2 of them after prolonged follow-up (5.5 and 30 y). Seven of 10 patients (70%) with high-grade nuclei metastasized as did all 4 patients with coagulative necrosis. Two of 17 (12%) patients with low-grade nuclei metastasized, and both had unbiopsied contralateral tumors, which may have been the origin of the metastatic disease. In conclusion, SDH-deficient renal carcinoma is a rare and unique type of renal carcinoma, exhibiting stereotypical morphologic features in the great majority of cases and showing a strong relationship with SDH germline mutation. Although this tumor may undergo dedifferentiation and metastasize, sometimes after a prolonged delay, metastatic disease is rare in the absence of high-grade nuclear atypia or coagulative necrosis.

Pancreatic paraganglioma - a rare and dangerous entity. Vascular anatomy and impact on management

Pancreatic paragangliomas are extremely rare with less than 20 cases ever described in the world literature. There is no detailed report of the vascular anatomy in this entity and its possible impact on patient management. We present a case of large pancreatic head paraganlioma in a 53-year-old woman. The tumour had a predominant arterial blood supply via both the hepatic artery and the superior mesenteric artery. Complex inflow was complemented by supplementary branches from the right renal artery. The arteriovenous communications within the lesion represented the most dangerous aspect of excision and the tumour removal was accompanied with a considerable blood loss. After pancreaticoduodenectomy, patient experienced transient elevation of liver function tests with no other identifiable cause than a change in portal haemodynamics. It is advisable that the precise knowledge of vascular anatomy in pancreatic head paraganglioma should be obtained prior to any intervention.

Perioperative management of pheochromocytoma and catecholamine-induced dilated cardiomyopathy in a pediatric patient

Dilated cardiomyopathy resulting from pheochromocytoma-mediated catecholamine excess poses a unique challenge to heart failure management. Although early screening of patients with familial neoplastic syndromes at risk for pheochromocytoma may facilitate early resection, the resultant manifestations of prolonged catecholamine excess among patients with undiagnosed pheochromocytoma may lead to myocardial fibrosis with both systolic and diastolic dysfunction. Furthermore, the hemodynamic effects of catecholamine excess exacerbate the risks of perioperative hemodynamic instability in the setting of such myocardial depression. This report describes an approach to the perioperative care of a child who had pheochromocytoma and catecholamine-induced cardiomyopathy with ventricular dysfunction refractory to medical management.

Pheochromocytoma and paraganglioma: an endocrine society clinical practice guideline

OBJECTIVE

The aim was to formulate clinical practice guidelines for pheochromocytoma and paraganglioma (PPGL).

PARTICIPANTS

The Task Force included a chair selected by the Endocrine Society Clinical Guidelines Subcommittee (CGS), seven experts in the field, and a methodologist. The authors received no corporate funding or remuneration.

EVIDENCE

This evidence-based guideline was developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe both the strength of recommendations and the quality of evidence. The Task Force reviewed primary evidence and commissioned two additional systematic reviews.

CONSENSUS PROCESS

One group meeting, several conference calls, and e-mail communications enabled consensus. Committees and members of the Endocrine Society, European Society of Endocrinology, and Americal Association for Clinical Chemistry reviewed drafts of the guidelines.

CONCLUSIONS

The Task Force recommends that initial biochemical testing for PPGLs should include measurements of plasma free or urinary fractionated metanephrines. Consideration should be given to preanalytical factors leading to false-positive or false-negative results. All positive results require follow-up. Computed tomography is suggested for initial imaging, but magnetic resonance is a better option in patients with metastatic disease or when radiation exposure must be limited. (123)I-metaiodobenzylguanidine scintigraphy is a useful imaging modality for metastatic PPGLs. We recommend consideration of genetic testing in all patients, with testing by accredited laboratories. Patients with paraganglioma should be tested for SDHx mutations, and those with metastatic disease for SDHB mutations. All patients with functional PPGLs should undergo preoperative blockade to prevent perioperative complications. Preparation should include a high-sodium diet and fluid intake to prevent postoperative hypotension. We recommend minimally invasive adrenalectomy for most pheochromocytomas with open resection for most paragangliomas. Partial adrenalectomy is an option for selected patients. Lifelong follow-up is suggested to detect recurrent or metastatic disease. We suggest personalized management with evaluation and treatment by multidisciplinary teams with appropriate expertise to ensure favorable outcomes.

Non-functioning paraganglioma of the urinary bladder: A case report and review of the literature

Paragangliomas are extra-adrenal tumors of the autonomic nervous system and may be found within the skull base, neck, mediastinum and periaortic region. Paragangliomas of the urinary bladder are rare, and non-functioning bladder paraganglioma is even rarer and not easily recognized. Histological examination is often key in leading to a definitive diagnosis. The current report presents a case of a 28-year-old female with urinary bladder paraganglioma. The patient presented with no classical signs and symptoms, and these were only appreciated following histological examination of a transurethral resection specimen that elucidated the correct diagnosis. In the present report, the clinical features, diagnosis, management and pathological observations of paraganglioma of the urinary bladder are discussed.

Non-pheochromocytoma (PCC)/paraganglioma (PGL) tumors in patients with succinate dehydrogenase-related PCC-PGL syndromes: a clinicopathological and molecular analysis

OBJECTIVE

Although the succinate dehydrogenase (SDH)-related tumor spectrum has been recently expanded, there are only rare reports of non-pheochromocytoma/paraganglioma tumors in SDHx-mutated patients. Therefore, questions still remain unresolved concerning the aforementioned tumors with regard to their pathogenesis, clinicopathological phenotype, and even causal relatedness to SDHx mutations. Absence of SDHB expression in tumors derived from tissues susceptible to SDH deficiency is not fully elucidated.

DESIGN AND METHODS

Three unrelated SDHD patients, two with pituitary adenoma (PA) and one with papillary thyroid carcinoma (PTC), and three SDHB patients affected by renal cell carcinomas (RCCs) were identified from four European centers. SDHA/SDHB immunohistochemistry (IHC), SDHx mutation analysis, and loss of heterozygosity analysis of the involved SDHx gene were performed on all tumors. A cohort of 348 tumors of unknown SDHx mutational status, including renal tumors, PTCs, PAs, neuroblastic tumors, seminomas, and adenomatoid tumors, was investigated by SDHB IHC.

RESULTS

Of the six index patients, all RCCs and one PA displayed SDHB immunonegativity in contrast to the other PA and PTC. All immunonegative tumors demonstrated loss of the WT allele, indicating bi-allelic inactivation of the germline mutated gene. Of 348 tumors, one clear cell RCC exhibited partial loss of SDHB expression.

CONCLUSIONS

These findings strengthen the etiological association of SDHx genes with pituitary neoplasia and provide evidence against a link between PTC and SDHx mutations. Somatic deletions seem to constitute the second hit in SDHB-related renal neoplasia, while SDHx alterations do not appear to be primary drivers in sporadic tumorigenesis from tissues affected by SDH deficiency.

Hypoxia-inducible factor signaling in pheochromocytoma: turning the rudder in the right direction

Many solid tumors, including pheochromocytoma (PHEO) and paraganglioma (PGL), are characterized by a (pseudo)hypoxic signature. (Pseudo)hypoxia has been shown to promote both tumor progression and resistance to therapy. The major mediators of the transcriptional hypoxic response are hypoxia-inducible factors (HIFs). High levels of HIFs lead to transcription of hypoxia-responsive genes, which are involved in tumorigenesis. PHEOs and PGLs are catecholamine-producing tumors arising from sympathetic- or parasympathetic-derived chromaffin tissue. In recent years, substantial progress has been made in understanding the metabolic disturbances present in PHEO and PGL, especially because of the identification of some disease-susceptibility genes. To date, fifteen PHEO and PGL susceptibility genes have been identified. Based on the main transcription signatures of the mutated genes, PHEOs and PGLs have been divided into two clusters, pseudohypoxic cluster 1 and cluster 2, rich in kinase receptor signaling and protein translation pathways. Although these two clusters seem to show distinct signaling pathways, recent data suggest that both clusters are interconnected by HIF signaling as the important driver in their tumorigenesis, and mutations in most PHEO and PGL susceptibility genes seem to affect HIF-α regulation and its downstream signaling pathways. HIF signaling appears to play an important role in the development and growth of PHEOs and PGLs, which could suggest new therapeutic approaches for the treatment of these tumors.

Warburg effect's manifestation in aggressive pheochromocytomas and paragangliomas: insights from a mouse cell model applied to human tumor tissue

A glycolytic profile unifies a group of pheochromocytomas and paragangliomas (PHEOs/PGLs) with distinct underlying gene defects, including von Hippel-Lindau (VHL) and succinate dehydrogenase B (SDHB) mutations. Nevertheless, their tumor aggressiveness is distinct: PHEOs/PGLs metastasize rarely in VHL-, but frequently in SDHB-patients. To date, the molecular mechanisms causing the more aggressive phenotype in SDHB-PHEOs/PGLs remain largely unknown. Recently, however, an excellent model to study aggressive PHEOs (mouse tumor tissue (MTT) cells) has been developed from mouse PHEO cells (MPC). We employed this model for a proteomics based approach to identify changes characteristic for tumor aggressiveness, which we then explored in a homogeneous set of human SDHB- and VHL-PHEOs/PGLs. The increase of glucose transporter 1 in VHL, and of hexokinase 2 in VHL and SDHB, confirmed their glycolytic profile. In agreement with the cell model and in support of decoupling of glycolysis, the Krebs cycle and oxidative phosphorylation (OXPHOS), SDHB tumors showed increased lactate dehydrogenase levels. In SDHB-PGLs OXPHOS complex activity was increased at complex III and, as expected, decreased at complex II. Moreover, protein and mRNA expression of all tested OXPHOS-related genes were higher in SDHB- than in VHL-derived tumors. Although there was no direct evidence for increased reactive oxygen species production, elevated superoxide dismutase 2 expression may reflect elevated oxidative stress in SDHB-derived PHEOs/PGLs. For the first time, we show that despite dysfunction in complex II and evidence for a glycolytic phenotype, the Warburg effect does not seem to fully apply to SDHB-PHEOs/PGLs with respect to decreased OXPHOS. In addition, we present evidence for increased LDHA and SOD2 expression in SDHB-PHEOs/PGLs, proteins that have been proposed as promising therapeutic targets in other cancers. This study provides new insight into pathogenic mechanisms in aggressive human PHEOs/PGLs, which may lead to identifying new diagnostic and prognostic markers in the near future.

Impaired TCA cycle flux in mitochondria in skeletal muscle from type 2 diabetic subjects: marker or maker of the diabetic phenotype?

The diabetic phenotype is complex, requiring elucidation of key initiating defects. Recent research has shown that diabetic myotubes express a primary reduced tricarboxylic acid (TCA) cycle flux. A reduced TCA cycle flux has also been shown both in insulin resistant offspring of T2D patients and exercising T2D patients in vivo. This review will discuss the latest advances in the understanding of the molecular mechanisms regulating the TCA cycle with focus on possible underlying mechanism which could explain the impaired TCA flux in insulin resistant human skeletal muscle in type 2 diabetes. A reduced TCA is both a marker and a maker of the diabetic phenotype.

An update on the genetics of pheochromocytoma

Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are rare neuroendocrine tumors. About 30% or more of them are thought to be of inherited origin due to germ-line mutations in at least 10 well-characterized genes. There are data linking specific genotypes of these tumors to specific locations, typical biochemical phenotypes or future clinical behaviors. Conversely, clinical features, catecholamine production and immunohistochemistry evaluation can help with the proper order of genetic testing for PHEO and PGL. The identification of a germ-line mutation can lead to an early diagnosis, appropriate treatment, regular surveillance and better prognosis not only for the patient but also for their family members. Moreover, the latest discoveries in molecular pathogenesis of these tumors will provide an important basis for future personalized therapy.

Targeting cancer metabolism--aiming at a tumour's sweet-spot

Targeting cancer metabolism has emerged as a hot topic for drug discovery. Most cancers have a high demand for metabolic inputs (i.e. glucose/glutamine), which aid proliferation and survival. Interest in targeting cancer metabolism has been renewed in recent years with the discovery that many cancer-related (e.g. oncogenic and tumour suppressor) pathways have a profound effect on metabolism and that many tumours become dependent on specific metabolic processes. Considering the recent increase in our understanding of cancer metabolism and the increasing knowledge of the enzymes and pathways involved, the question arises: could metabolism be cancer's Achilles heel? During recent years, interest into the possible therapeutic benefit of targeting metabolic pathways in cancer has increased dramatically with academic and pharmaceutical groups actively pursuing this aspect of tumour physiology. Therefore, what has fuelled this revived interest in targeting cancer metabolism and what are the major advances and potential challenges faced in the race to develop new therapeutics in this area? This review will attempt to answer these questions by summarising recent developments in this field. We aim to illustrate why we, and others, believe that targeting metabolism in cancer presents such a promising therapeutic rationale.

Pheochromocytomas and paragangliomas: assessment of malignant potential

Pheochromocytomas and paragangliomas (PPGLs) are rare catecholamine-secreting tumors which arise from the adrenal glands or sympathetic neuronal tissue. Malignant transformation of these tumors occurs in a significant proportion and may therefore lower overall survival rates. In patients with PPGLs it is impossible to identify malignant disease without the presence of metastatic disease, something which can occur as long as 20 years after initial surgery. Early identification of malignant disease would necessitate a more aggressive treatment approach, something which may result in better disease outcome. We have therefore reviewed possible predictors of malignancy and current developments in order to help clinicians to swiftly assess malignant potential in patients with PPGLs. Currently, there is no absolute marker which can objectively reflect malignant potential. Tumor size is the most reliable predictor and should therefore be used as the baseline characteristic. The combination of various clinical markers (extra-adrenal disease and post-operative hypertension), biochemical markers (high dopamine, high norepinephrine and epinephrine to total catecholamine ratio) and/or histological markers (SNAIL, microRNAs and/or microarray results) can raise or lower the suspicion of malignancy. Furthermore, we discuss how clinical markers may affect biochemical results linked to malignancy, how biochemical results may distinguish hereditary syndromes, the role of imaging in determining malignant potential and tumor detection, and recent results of proposed histological markers.

Genetic testing for pheochromocytoma

Pheochromocytomas (PHEOs) and paragangliomas (PGLs) are rare, catecholamine-producing tumors that are usually sporadic. However, about 30% of these tumors have been identified as being of inherited origin. To date, nine genes have been confirmed as participating in PHEO or PGL tumorigenesis. Germline mutations were found in 100% of syndromic cases and in about 90% of patients with positive familial history. In nonsyndromic patients with apparently sporadic tumors, genetic mutations have been found in up to 27%, and genetic testing is now recommended for all patients with PHEOs and PGLs. Patients with syndromic lesions, a positive family history, or both should be tested for the appertaining gene. Recent discoveries have shown that the order of tested genes in nonsyndromic, nonfamilial cases can be based on histologic evaluation, location, and the biochemical phenotype of PHEOs and PGLs--the "rule of three." Identification of a gene mutation may lead to early diagnosis and treatment, regular surveillance, and a better prognosis for patients and their relatives.

Catecholamine metabolomic and secretory phenotypes in phaeochromocytoma

Phaeochromocytomas and paragangliomas (PPGLs) are highly heterogeneous tumours with variable catecholamine biochemical phenotypes and diverse hereditary backgrounds. This analysis of 18 catecholamine-related plasma and urinary biomarkers in 365 patients with PPGLs and 846 subjects without PPGLs examined how catecholamine metabolomic profiles are impacted by hereditary background and relate to variable hormone secretion. Catecholamine secretion was assessed in a subgroup of 156 patients from whom tumour tissue was available for measurements of catecholamine contents. Among all analytes, the free catecholamine O-methylated metabolites measured in plasma showed the largest tumour-related increases relative to the reference group. Patients with tumours due to multiple endocrine neoplasia type 2 and neurofibromatosis type 1 (NF1) showed similar catecholamine metabolite and secretory profiles to patients with adrenaline-producing tumours and no evident hereditary background. Tumours from these three patient groups contained higher contents of catecholamines, but secreted the hormones at lower rates than tumours that did not contain appreciable adrenaline, the latter including PPGLs due to von Hippel-Lindau (VHL) and succinate dehydrogenase (SDH) gene mutations. Large increases of plasma dopamine and its metabolites additionally characterised patients with PPGLs due to the latter mutations, whereas patients with NF1 were characterised by large increases in plasma dihydroxyphenylglycol and dihydroxyphenylacetic acid, the deaminated metabolites of noradrenaline and dopamine. This analysis establishes the utility of comprehensive catecholamine metabolite profiling for characterising the distinct and highly diverse catecholamine metabolomic and secretory phenotypes among different groups of patients with PPGLs. The data further suggest developmental origins of PPGLs from different populations of chromaffin cell progenitors.

Metastatic paraganglioma

Paragangliomas (PGLs) are chromaffin cell tumors arising from ganglia; when arising in the adrenal gland they are called pheochromocytomas. In recent years the opinion that metastatic disease is rare in PGL had to be revised, particularly in patients presenting with extra-adrenal PGL, with PGLs exceeding 5 cm in diameter, and/or those carrying an SDHB germline mutation. Metastases are expected to be present at the time of diagnosis in more than 10% of these patients. Measurement of plasma and urinary metanephrine levels is well established in diagnosing PGL. Recently, a dopaminergic phenotype (excess dopamine or methoxytyramine) was recognized as a good indicator of metastatic disease. Vast progress in targeted positron emission tomography (PET) imaging (eg, (18)F-FDA, (18)F-FDOPA, (18)F-FDG) now allows for reliable early detection of metastatic disease. However, once metastases are present, treatment options are limited. Survival of patients with metastatic PGL is variable, and frequently short. Here we review recent advances involving findings about the genetic background, the molecular pathogenesis, new diagnostic indicators, pathologic markers, and emerging treatment options for metastatic PGL.

Primary retroperitoneal paraganglioma simulating a pancreatic mass: a case report and review of the literature

Paragangliomas are extra-adrenal tumors of the autonomic nervous system and may be found within the skull base, neck, chest, and abdomen. When presenting within the abdominal cavity, they may arise as a primary retroperitoneal neoplasm and can mimic vascular malformations or other conditions related to specific retroperitoneal organs such as the pancreas, kidneys, or adrenals. Retroperitoneal paragangliomas are mostly benign with good prognosis; however, they can present with abdominal pain, palpable mass, or hypertensive episodes. Patients should be initially evaluated with catecholamine levels, followed by computed tomography or magnetic resonance imaging to locate the primary lesion. Surgical excision remains the mainstay of treatment, although advanced disease and proximity to vital organs can make excision difficult or impossible. This case report describes a patient who initially underwent work up for a suspected pancreatic head mass which was discovered to be a retroperitoneal paraganglioma by frozen section.

The evolving field of tyrosine kinase inhibitors in the treatment of endocrine tumors

Activation of tyrosine kinase receptors (TKRs) and their related pathways has been associated with development of endocrine tumors. Compounds that target and inactivate the kinase function of these receptors, tyrosine kinase inhibitors (TKIs), are now being applied to the treatment of endocrine tumors. Recent clinical trials of TKIs in patients with advanced thyroid cancer, islet cell carcinoma, and carcinoid have shown promising preliminary results. Significant reductions in tumor size have been described in medullary and papillary thyroid carcinoma, although no complete responses have been reported. Case reports have described significant tumor volume reductions of malignant pheochromocytomas and paragangliomas. In addition, these compounds showed an initial tumoricidal or apoptotic response followed by long-term static effects on tumor growth. Despite the promising preliminary results, this class of therapeutic agents has a broad spectrum of adverse effects, mediated by inhibition of kinase activities in normal tissues. These adverse effects will have to be balanced with their benefit in clinical use. New strategies will have to be applied in clinical research to achieve optimal benefits. In this review, we will address the genetic alterations of TKRs, the rationale for utilizing TKIs for endocrine tumors, and current information on tumor and patient responses to specific TKIs. We will also discuss the adverse effects related to TKI treatment and the mechanisms involved. Finally, we will summarize the challenges associated with use of this class of compounds and potential solutions.

New imaging approaches to phaeochromocytomas and paragangliomas

Formerly used concepts for phaeochromocytomas and paragangliomas have been challenged by recent discoveries that at least 24% of tumours are familial and thereby often multiple in various locations throughout the body. Furthermore, tumours are often malignant and perhaps more aggressive if associated with SDHB gene mutations. Some paragangliomas are clinically silent and may present only with dopamine hypersecretion. In the current era where CT and MRI are more commonly used, tumours are more often found as incidentalomas and MRI may be less specific for phaeochromocytoma and paraganglioma than previously thought. Because of unique tumour characteristics (e.g. the presence of cell membrane and intracellular vesicular norepinephrine transporters) these tumours were 'born' to be imaged by means of specific functional imaging approaches. Moreover, additional recent discoveries related to apoptosis, hypoxia, acidosis, anaerobic glycolysis and angiogenesis, often disturbed in tumour cells, open new options and challenges to specifically image phaeochromocytomas and paragangliomas and possibly link those results to their pathophysiology, genotypic alterations and metastatic potential. Functional imaging, especially represented by positron emission tomography (PET), offers an excellent approach by which tumour-specific processes can be detected, evaluated and seen in the context of tumour-specific behaviour and its genetic signature. In this review, we address the recent developments in new functional imaging modalities for phaeochromocytoma and paraganglioma and provide the reader with suggested imaging approaches in various phaeochromocytomas and paragangliomas of sympathetic origin. Current imaging algorithms of head and neck parasympathetic paragangliomas are not discussed. Finally, this review outlines some future perspectives of functional imaging of these tumours.