Genetic basis of phaeochromocytoma and paraganglioma

[Paragangliomas - Essentials for the ENT Doctor]

Paragangliomas of the head and neck area should be detected early and diagnosed in their complexity at specialized centers, treated and, in the presence of paraganglioma syndrome, cared for for life. The continuing education article focuses in an abridged form on the most important basics of a complex clinical picture and deals with both sporadic head and neck paragangliomas and hereditary paraganglioma syndromes. It contains concise recommendations regarding genetic testing, the diagnosis of multicentric tumors, the multidisciplinary treatment approach and the need for lifelong monitoring.

Research progress on the pathogenesis of the SDHB mutation and related diseases

With the improvement of genetic testing technology in diseases in recent years, researchers have a more detailed and clear understanding of the source of cancers. Succinate dehydrogenase B (SDHB), a mitochondrial gene, is related to the metabolic activities of cells and tissues throughout the body. The mutations of SDHB have been found in pheochromocytoma, paraganglioma and other cancers, and is proved to affect the occurrence and progress of those cancers due to the important structural functions. The importance of SDHB is attracting more and more attention of researchers, however, reviews on the structure and function of SDHB, as well as on the mechanism of its carcinogenesis is inadequate. This paper reviews the relationship between SDHB mutations and related cancers, discusses the molecular mechanism of SDHB mutations that may lead to tumor formation, analyzes the mutation spectrum, structural domains, and penetrance of SDHB and sorts out some of the previously discovered diseases. For the patients with SDHB mutation, it is recommended that people in SDHB mutation families undergo regular genetic testing or SDHB immunohistochemistry (IHC). The purpose of this paper is hopefully to provide some reference and help for follow-up researches on SDHB.

Image-Guided Precision Medicine in the Diagnosis and Treatment of Pheochromocytomas and Paragangliomas

In this comprehensive review, we aimed to discuss the current state-of-the-art medical imaging for pheochromocytomas and paragangliomas (PPGLs) diagnosis and treatment. Despite major medical improvements, PPGLs, as with other neuroendocrine tumors (NETs), leave clinicians facing several challenges; their inherent particularities and their diagnosis and treatment pose several challenges for clinicians due to their inherent complexity, and they require management by multidisciplinary teams. The conventional concepts of medical imaging are currently undergoing a paradigm shift, thanks to developments in radiomic and metabolic imaging. However, despite active research, clinical relevance of these new parameters remains unclear, and further multicentric studies are needed in order to validate and increase widespread use and integration in clinical routine. Use of AI in PPGLs may detect changes in tumor phenotype that precede classical medical imaging biomarkers, such as shape, texture, and size. Since PPGLs are rare, slow-growing, and heterogeneous, multicentric collaboration will be necessary to have enough data in order to develop new PPGL biomarkers. In this nonsystematic review, our aim is to present an exhaustive pedagogical tool based on real-world cases, dedicated to physicians dealing with PPGLs, augmented by perspectives of artificial intelligence and big data.

From Diagnosis to Therapy-PET Imaging for Pheochromocytomas and Paragangliomas

PURPOSE OF REVIEW

Pheochromocytoma and paraganglioma (PPGLs) are neuroendocrine tumors with diverse clinical presentations. PPGLs can be sporadic but often are associated with various syndromes, which can have variable clinical presentations. A thorough workup is therefore critical for staging, treatment, and follow-up. Imaging is an essential part of the workup and diagnosis of PPGLs.

RECENT FINDINGS

Improvements in cross-sectional imaging with radionuclides have increased specificity and sensitivity for identifying and treating PPGLs. Furthermore, a variety of targets on PPGLs has allowed for optimal imaging with radionuclides that can be used for staging and treatment. Currently, radionuclides are being evaluated for staging and treatment of PPGLs. Developing novel radionuclides that can identify disease sites and target them simultaneously provides a potential for improving survival and outcomes in patients with PPGLs. Given the clinical diversity among PPGLs, expanding the therapeutic arsenal against locally advanced or metastatic PPGLs can allow clinicians to evaluate and treat PPGLs thoroughly.

Surgical Resection of Pheochromocytomas and Paragangliomas is Associated with Lower Cholesterol Levels

BACKGROUND

Catecholamine excess in patients with pheochromocytomas or paragangliomas (PPGLs) can lead to hypertension, diabetes and hyperlipidemia. The aim was to investigate the prevalence of hyperlipidemia and the effect of surgical resection.

METHODS

One hundred and thirty-two patients with PPGLs underwent an operation at the National Institutes of Health from 2009 to 2016, of which 54 patients met the inclusion criteria. Clinical demographics, BMI, genetic mutations, tumor size, perioperative catecholamine levels and perioperative lipid panels were retrospectively reviewed. Spearman correlation between catecholamines and lipid levels was evaluated. Paired Wilcoxon and paired t test were used to analyze differences in pre- and postoperative lipid levels.

RESULTS

Preoperatively, 51 patients (94.4%) had elevated catecholamines, thirteen (24.1%) had elevated total cholesterol (TC) (>200 mg/dL), nine (16.6%) had elevated LDL (>130 mg/dL) and ten (18.5%) had elevated triglycerides (>150 mg/dL). Serum and urinary metanephrine levels were positively associated with TC (r = 0.2792, p = 0.0372 and r = 0.4146, p = 0.0031, respectively) and LDL levels (r = 0.2977, p = 0.0259 and r = 0.4434, p = 0.0014, respectively). Mean TC decreased from 176.4 to 166.3 mg/dL (p = 0.0064) and mean HDL decreased from 56.7 to 53.2 mg/dL (p = 0.0253) after PPGL resection (median 3.1 months (range 1.3-50.2) between lipid panels). Most patients with elevated TC (76.9%) had improvement with mean TC decreasing from 225 to 200.2 mg/dL (p = 0.0230). Of patients with elevated LDL, 66.7% had improvement with mean LDL decreasing from 149 to 131.1 mg/dL (p = 0.0313).

CONCLUSIONS

The prevalence of hyperlipidemia in patients with PPGLs is 46%. Future prospective studies are needed to determine whether surgical resection improves TC and/or LDL levels.

[An incidental finding of retrocaval extraadrenal pheochromocytoma]

As part of diagnostic work-up of a 71-year-old patient with resistant hypertension, an extraadrenal mass was found. After further imaging and biochemical evaluation an extraadrenal pheochromocytoma was diagnosed and after alpha-receptor blockade was removed via posterior approach laparoscopically in the course. The pheochromocytoma is a rare catecholamine-producing tumor with an incidence of 1-2 per 100 000. In about 1-25 % it is located extraadrenal. Establishing the diagnosis is dependent on the demonstration of significant catecholamine excess. Afterwards imaging with CT or MRI should be performed. After administration of alpha-blockers, the complete surgical resection is the treatment of choice.

The characterization of pheochromocytoma and its impact on overall survival in multiple endocrine neoplasia type 2

CONTEXT

Pheochromocytoma (PHEO) occurs in 50% of patients with multiple endocrine neoplasia type 2 (MEN2). It is unknown if the presence of PHEO is associated with more aggressive medullary thyroid cancer (MTC).

OBJECTIVE

To present our experience with MEN2 PHEO and evaluate whether PHEO impacts MTC overall survival in patients with RET codon 634 mutations.

DESIGN

We performed a retrospective chart review of MEN2 patients at MD Anderson Cancer Center from 1960 through 2012.

PATIENTS

The study group comprised 85 patients (group 1) with MEN2-associated PHEO. Of these, 59 patients (subgroup 1) with RET codon 634 mutations were compared to 48 patients (group 2) with RET codon 634 mutations, but without MEN2-associated PHEO.

MAIN OUTCOME MEASURES

Of 85 patients with MEN2 and PHEO, 70 had MEN2A and 15 had MEN2B. Median age at PHEO diagnosis was 32 years. The initial manifestation of MEN2 was MTC in 60% of patients, synchronous MTC and PHEO in 34%, and PHEO in 6% of patients. Of patients, 72% had bilateral PHEO, and most tumors were synchronous (82%). Subgroup analysis of MEN2 patients with and without PHEO, who were carriers of RET codon 634, the most common mutation with PHEO, showed no significant differences in the stage of MTC at initial diagnosis. The median follow-up time for patients with PHEO was 249 months and without PHEO was 67 months (P < .01). Survival analyses among RET 634 carriers did not show shorter survival for patients with PHEO. The median survival time for patients with PHEO was 499 months and without PHEO was 444 months (P < .05).

CONCLUSIONS

PHEO in MEN2 patients are usually bilateral and unlikely to be metastatic. Subgroup analysis of patients with RET 634 mutations with and without PHEO showed that PHEO was not associated with a more advanced stage of MTC at diagnosis or a shorter survival.

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.

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.

Role of ultrasound and color Doppler imaging in the detection of carotid paragangliomas

INTRODUCTION

Carotid body paragangliomas (PGLs) are highly vascularized lesions that arise from the paraganglia located at the carotid bifurcation.

PURPOSE

To evaluate the usefulness of gray-scale ultrasound (US) and color Doppler ultrasound (CDUS) in the detection and follow-up of carotid PGLs of the neck.

MATERIALS AND METHODS

The authors retrospectively reviewed US and CDUS examinations of the neck performed in 40 patients with PGL syndrome type 1 and single or bilateral neck PGLs confirmed by CT or MRI; the patients had a total of 60 PGLs of the neck. US and CDUS outcome was compared to the outcome of second-line imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT). The following findings were considered: presence/absence of focal lesions at US imaging and difference in maximum diameter of the lesion measured at US and MRI/CT. Results were compared using the Student's t-test.

RESULTS

Of the 60 PGLs of the neck only 5 (8.3%) were not visualized at US or CDUS examination. The difference in maximum diameter of these lesions measured at CT/MRI and US/CDUS ranged between -5 mm and +16 mm (mean difference 2.2 ± 6.0). This difference was statistically significant (p = 0.008).

CONCLUSIONS

US and CDUS are useful methods for identifying carotid PGLs also measuring less than 10 mm in diameter. However, diagnostic accuracy of US and CDUS is reduced in the measurement of the exact dimensions of the lesions.

Clinical and imaging overview of functional adrenal neoplasms

Adrenal adenoma, adrenocortical carcinoma, pheochromocytoma and neuroblastoma are four discrete adrenal neoplasms that have the potential for functional activity. Functional adrenal neoplasms can secrete cortisol, aldosterone, sex hormones or catecholamines. These heterogeneous groups of tumors show varied biological behavior and clinical outcomes. These neoplasms are encountered with increasing clinical frequency as a result of an expansion in the volume of medical imaging carried out. The clinical presentation, including prognosis and treatment options, and the imaging features of these neoplasms are discussed. The key radiological observations of each of these neoplasms are shown using multimodality images. Familiarity with the clinical and imaging features of these neoplasms improves diagnosis, and facilitates appropriate clinical decision-making and patient management.

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.

Succinate dehydrogenase gene mutations are strongly associated with paraganglioma of the organ of Zuckerkandl

Organ of Zuckerkandl paragangliomas (PGLs) are rare neuroendocrine tumors that are derived from chromaffin cells located around the origin of the inferior mesenteric artery extending to the level of the aortic bifurcation. Mutations in the genes encoding succinate dehydrogenase subunits (SDH) B, C, and D (SDHx) have been associated with PGLs, but their contribution to PGLs of the organ of Zuckerkandl PGLs is not known. We aimed to describe the clinical presentation of patients with PGLs of the organ of Zuckerkandl and investigate the prevalence of SDHx mutations and other genetic defects among them. The clinical characteristics of 14 patients with PGL of the organ of Zuckerkandl were analyzed retrospectively; their DNA was tested for SDHx mutations and deletions. Eleven out of 14 (79%) patients with PGLs of the organ of Zuckerkandl were found to have mutations in the SDHB (9) or SDHD (2) genes; one patient was found to have the Carney-Stratakis syndrome (CSS), and his PGL was discovered during surgery for gastrointestinal stromal tumor. Our results show that SDHx mutations are prevalent in pediatric and adult PGLs of the organ of Zuckerkandl. Patients with PGLs of the organ of Zuckerkandl should be screened for SDHx mutations and the CSS; in addition, asymptomatic carriers of an SDHx mutation among the relatives of affected patients may benefit from tumor screening for early PGL detection.

Immunohistochemistry for SDHB triages genetic testing of SDHB, SDHC, and SDHD in paraganglioma-pheochromocytoma syndromes

Up to 30% of pheochromocytomas and paragangliomas are associated with germline RET, Von Hippel-Lindau (VHL), neurofibromatosis type I (NF1), and succinate dehydrogenase subunits (SDHB, SDHC, and SDHD) mutations. Genetic testing allows familial counseling and identifies subjects at high risk of malignancy (SDHB mutations) or significant multiorgan disease (RET, VHL, or NF1). However, conventional genetic testing for all loci is burdensome and costly. We performed immunohistochemistry for SDHB on 58 tumors with known SDH mutation status. We defined positive as granular cytoplasmic staining (a mitochondrial pattern), weak diffuse as a cytoplasmic blush lacking definite granularity, and negative as completely absent staining in the presence of an internal positive control. All 12 SDH mutated tumors (6 SDHB, 5 SDHD, and 1 SDHC) showed weak diffuse or negative staining. Nine of 10 tumors with known mutations of VHL, RET, or NF1 showed positive staining. One VHL associated tumor showed weak diffuse staining. Of 36 tumors without germline mutations, 34 showed positive staining. One paraganglioma with no known SDH mutation but clinical features suggesting familial disease was negative, and one showed weak diffuse staining. We also performed immunohistochemistry for SDHB on 143 consecutive unselected tumors of which 21 were weak diffuse or negative. As SDH mutations are virtually always germline, we conclude that approximately 15% of all pheochromocytomas or paragangliomas are associated with germline SDH mutation and that immunohistochemistry can be used to triage genetic testing. Completely absent staining is more commonly found with SDHB mutation, whereas weak diffuse staining often occurs with SDHD mutation.

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.

Phaeochromocytomas and sympathetic paragangliomas

BACKGROUND

About 24 per cent of phaeochromocytomas (PCCs) and sympathetic paragangliomas (sPGLs) appear in familial cancer syndromes, including multiple endocrine neoplasia type 2, von Hippel-Lindau disease, neurofibromatosis type 1 and PCC-paraganglioma syndrome. Identification of these syndromes is of prime importance for patients and their relatives. Surgical resection is the treatment of choice for both PCC and sPGL, but controversy exists about the management of patients with bilateral or multiple tumours.

METHODS

Relevant medical literature from PubMed, Ovid and Embase websites until 2009 was reviewed for articles on PCC, sPGL, hereditary syndromes and their treatment.

DISCUSSION

Genetic testing for these syndromes should become routine clinical practice for those with PCC or sPGL. Patients should be referred to a clinical geneticist. Patients and family members with proven mutations should be entered into a standardized screening protocol. The preferred treatment of PCC and PGL is surgical resection; to avoid the lifelong consequences of bilateral adrenalectomy, cortex-sparing adrenalectomy is the treatment of choice.

Clinical aspects of SDHx-related pheochromocytoma and paraganglioma

Paragangliomas (PGLs) derive from either sympathetic chromaffin tissue in adrenal and extra-adrenal abdominal or thoracic locations, or from parasympathetic tissue of the head and neck. Mutations of nuclear genes encoding subunits B, C, and D of the mitochondrial enzyme succinate dehydrogenase (SDHB 1p35-p36.1, SDHC 1q21, SDHD 11q23) give rise to hereditary PGL syndromes PGL4, PGL3, and PGL1 respectively. The susceptibility gene for PGL2 on 11q13.1 remains unidentified. Mitochondrial dysfunction due to SDHx mutations have been linked to tumorigenesis by upregulation of hypoxic and angiogenesis pathways, apoptosis resistance and developmental culling of neuronal precursor cells. SDHB-, SDHC-, and SDHD-associated PGLs give rise to more or less distinct clinical phenotypes. SDHB mutations mainly predispose to extra-adrenal, and to a lesser extent, adrenal PGLs, with a high malignant potential, but also head and neck paragangliomas (HNPGL). SDHD mutations are typically associated with multifocal HNPGL and usually benign adrenal and extra-adrenal PGLs. SDHC mutations are a rare cause of mainly HNPGL. Most abdominal and thoracic SDHB-PGLs hypersecrete either norepinephrine or norepinephrine and dopamine. However, only some hypersecrete dopamine, are biochemically silent. The biochemical phenotype of SDHD-PGL has not been systematically studied. For the localization of PGL, several positron emission tomography (PET) tracers are available. Metastatic SDHB-PGL is the best localized by [(18)F]-fluorodeoxyglucose PET. The identification of SDHx mutations in patients with PGL is warranted for a tailor-made approach to the biochemical diagnosis, imaging, treatment, follow-up, and family screening.

Malignant paraganglioma associated with succinate dehydrogenase subunit B in an 8-year-old child: the age of first screening?

Several studies have shown that patients with succinate dehydrogenase subunit B (SDHB) mutations have a very high risk for developing malignant paragangliomas. However, there is no consensus of what age screening for paragangliomas should start. We report a case of an 8-year-old white girl with a 3-year history of catecholamine excess-related complaints who was diagnosed with a malignant SDHB-associated mediastinal paraganglioma. The patient presented with intermittent sweating, headache, nausea, vomiting, fatigue and weight loss that had been present since she was 5 years of age. A large posterior mediastinal mass measuring 6.4 cm x 3.1 cm x 4.6 cm was discovered on computed tomography (CT) and magnetic resonance imaging (MRI). Laboratory data included an elevated level of urine normetanephrine of 45,400 microg/g creatinine (upper reference limit 718 microg/g) and elevated level of plasma normetanephrine of 62.4 nmol/l (upper reference limit <0.90 nmol/l). She was diagnosed with a thoracic paraganglioma and subsequently underwent surgical removal of the tumor and two lymph nodes. Histopathologic examination confirmed metastatic paraganglioma. Postoperatively, her blood pressure normalized and plasma normetanephrine levels remained normal. Our patient first presented with paraganglioma-associated signs and symptoms at the young age of 5 years. This case clearly illustrates the need for increased vigilance and screening for paragangliomas in families with SDHB at a younger age than previously thought.

Familial pheochromocytomas and paragangliomas associated with mutations of the succinate dehydrogenase genes

Pheochromocytomas and other sympathetic paragangliomas are rare tumors of the adrenal gland or extra-adrenal chromaffin tissue. Mutations of the genes encoding three subunits of the mitochondrial enzyme succinate dehydrogenase give rise to hereditary paraganglioma. We will review the distinct clinical phenotypes of familial paraganglioma syndromes associated with mutations in genes encoding for three different subunits of succinate dehydrogenase. The current insights in optimal strategies for biochemical testing, tumor localization and therapy of paraganglioma will be discussed. Furthermore, we provide recommendations regarding genetic testing and tumor screening among relatives of patients with succinate dehydrogenase-related paraganglioma.