The succinate dehydrogenase genetic testing in a large prospective series of patients with paragangliomas

Current management of carotid body tumors

Carotid body tumors (CBTs) are neoplasms that occur at the bifurcation of the carotid artery and are pathologically classified as paragangliomas. In the 4th edition of the WHO classification, paragangliomas are categorized as neoplasms with malignant potential. Clinically, about 5% of CBTs present with malignant features such as metastasis. Currently, it is challenging to distinguish between tumors with benign courses and those that present malignantly. Recent advances in genetic testing have elucidated the genetic characteristics of paragangliomas, including carotid body tumors. Over 20 genes have been identified as being involved in tumor development. Particularly in head and neck paragangliomas, abnormalities in genes related to succinate dehydrogenase are frequently observed. Research is ongoing to understand the mechanisms by which these genes contribute to tumor development. The definitive treatment for CBTs is surgical resection. These tumors are prone to bleeding and often adhere firmly to the carotid artery, making intraoperative bleeding control challenging. The risk of lower cranial nerve paralysis is relatively high, and there is a risk of stroke because of manipulation of the carotid artery. Preoperative evaluation with angiography is essential, and a multi-disciplinary surgical team approach is necessary. In cases where the tumor is difficult to resect or has metastasized, radiation therapy or chemotherapy are employed. Clinical trials involving targeted molecular therapies and radiopharmaceuticals have recently been conducted, with some applied clinically. The development of various new treatments is anticipated, providing hope for therapeutic options in refractory cases.

Whole-body MRI in oncology: A comprehensive review

Whole-Body Magnetic Resonance Imaging (WB-MRI) has cemented its position as a pivotal tool in oncological diagnostics. It offers unparalleled soft tissue contrast resolution and the advantage of sidestepping ionizing radiation. This review explores the diverse applications of WB-MRI in oncology. We discuss its transformative role in detecting and diagnosing a spectrum of cancers, emphasizing conditions like multiple myeloma and cancers with a proclivity for bone metastases. WB-MRI's capability to encompass the entire body in a singular scan has ushered in novel paradigms in cancer screening, especially for individuals harboring hereditary cancer syndromes or at heightened risk for metastatic disease. Additionally, its contribution to the clinical landscape, aiding in the holistic management of multifocal and systemic malignancies, is explored. The article accentuates the technical strides achieved in WB-MRI, its myriad clinical utilities, and the challenges in integration into standard oncological care. In essence, this review underscores the transformative potential of WB-MRI, emphasizing its promise as a cornerstone modality in shaping the future trajectory of cancer diagnostics and treatment.

The evolutionary impact of childhood cancer on the human gene pool

Germline pathogenic variants associated with increased childhood mortality must be subject to natural selection. Here, we analyze publicly available germline genetic metadata from 4,574 children with cancer [11 studies; 1,083 whole exome sequences (WES), 1,950 whole genome sequences (WGS), and 1,541 gene panel] and 141,456 adults [125,748 WES and 15,708 WGS]. We find that pediatric cancer predisposition syndrome (pCPS) genes [n = 85] are highly constrained, harboring only a quarter of the loss-of-function variants that would be expected. This strong indication of selective pressure on pCPS genes is found across multiple lines of germline genomics data from both pediatric and adult cohorts. For six genes [ELP1, GPR161, VHL and SDHA/B/C], a clear lack of mutational constraint calls the pediatric penetrance and/or severity of associated cancers into question. Conversely, out of 23 known pCPS genes associated with biallelic risk, two [9%, DIS3L2 and MSH2] show significant constraint, indicating that they may monoallelically increase childhood cancer risk. In summary, we show that population genetic data provide empirical evidence that heritable childhood cancer leads to natural selection powerful enough to have significantly impacted the present-day gene pool.

High incidence of occult familial SDHD cases amongst Czech patients with head and neck paragangliomas

Introduction

Head and neck paragangliomas (HNPGLs) are rare neuroendocrine tumors, which are mostly benign in nature. Amongst all genes, Succinate Dehydrogenase Subunit D (SDHD) is the most commonly mutated in familial HNPGLs. In about 30% of HNPGLs, germline mutations in SDHD can also occur in the absence of positive family history, thus giving rise to "occult familial" cases. Our aim was to evaluate the pattern of SDHD germline mutations in Czech patients with HNPGLs.

Materials and methods

We analyzed a total of 105 patients with HNPGLs from the Otorhinolaryngology departments of 2 tertiary centers between 2006 - 2021. All underwent complex diagnostic work-up and were also consented for genetic analysis.

Results

Eighty patients aged 13-76 years were included; around 60% with multiple PGLs were males. Carotid body tumor was the most frequently diagnosed tumor. Germline SDHD mutation was found in only 12% of the Czech patients; approximately 78% of those harboring the mutation had negative family history. The mutation traits had higher affiliation for multiple tumors with nearly 70% patients of ≤ 40 years of age.

Conclusion

An SDHD mutation variant was shared amongst unrelated patients but no founder-effect was established. Our findings confirmed that the pattern of SDHD mutation distribution amongst HNPGLs in Czech Republic differs from most studies worldwide.

Research in the genetics of pheochromocytoma and paraganglioma: a bibliometric analysis from 2002 to 2022

Over the past two decades, there has been a significant growth in articles focusing on the genetics of pheochromocytoma and paraganglioma (PPGL). We used bibliometric methods to investigate the historical changes and trend in PPGL research. There was a total of 1263 articles published in English from 2002 to 2022 included in our study. The number of annual publications and citations in this field has been increasing in the past 20 years. Furthermore, most of the publications originated from the European countries and the United States. The co-occurrence analysis showed close cooperation between different countries, institutions, or authors. The dual-map discipline analysis revealed that majority articles focused on four disciplines: #2 (Medicine, Medical, Clinical), #4 (Molecular, Biology, Immunology), #5 (Health, Nursing, Medicine), and #8 (Molecular, Biology, Genetics). The hotspot analysis revealed the keywords that have been landmark for PPGL genetics research in different time periods, and there was continued interest in gene mutations, especially on SDHX family genes. In conclusion, this study displays the current status of research and future trends in the genetics of PPGL. In future, more in-depth research should concentrate on crucial mutation genes and their specific mechanisms to assist in molecular target therapy. It is hoped that this study may help to provide directions for future research on genes and PPGL.

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.

Reduced Risk of Corporal Tumors in Patients With Head and Neck Paragangliomas With p.Pro81Leu Mutations

OBJECTIVE

Patients with head and neck paragangliomas who are positive for the SDHD p.Pro81Leu (P81L) mutation are thought to have a distinct phenotype from other SDHx mutations, but few studies have focused on this mutation. The objective of this study was to determine the hazard of developing a second primary, metastatic, or recurrent paraganglioma in SDHx patients with or without P81L.

STUDY DESIGN

Retrospective chart review of 60 patients with head and neck paragangliomas and genetic testing, followed for a median of 9 years.

SETTING

Single academic medical center.

METHODS

Univariable Cox proportional hazards regression evaluated second primary and recurrent paragangliomas in patients with SDHD P81L, SDHx non-P81L, and nonhereditary paraganglioma.

RESULTS

This series comprised 31 patients without SDHx, 14 with SDHD P81L, and 15 with other SDHx mutations. At a median 9 years of follow-up, corporal (not head and neck) second primary paragangliomas occurred in 31% of patients with SDHx non-P81L mutations, compared with 0% and 4% of patients with SDHD P81L and without SDHx mutations, respectively. Second corporal paragangliomas were more likely in patients with SDHx non-P81L mutations than in those without a mutation (hazard ratio = 5.461, 95% confidence interval: 0.596-50.030, p = .13).

CONCLUSION

This is the first study to report a lower likelihood of corporal tumors for patients with head and neck paragangliomas with SDH mutations positive for P81L. Larger studies are needed to determine if head and neck paraganglioma patients with P81L qualify for less intensive imaging surveillance to screen for second primary paragangliomas outside the head and neck.

Genotype-phenotype associations in paragangliomas of the temporal bone in a multi-ethnic cohort

BACKGROUND

Temporal bone paragangliomas are rare tumours with variable presentation that can be hereditary. Identification of clinical and genetic factors of aggressive tumour behaviour is important.

OBJECTIVE

To determine the underlying genetic mutations and genotype/phenotype correlations in a multi-ethnic population of South Florida with sporadic temporal bone paragangliomas.

METHODS

In a cohort of glomus tympanicum (GT) and glomus jugulare (GJ) cases, we assessed the frequency of pathogenic single nucleotide variants, insertions, deletions, and duplications in coding exons of genes that have been associated with paragangliomas (SDHB, SDHC, SDHD, SDHA, SDHAF2, RET, NF1, VHL, TMEM127, and MAX).

RESULTS

None of the 12 GT cases had mutations. Among 13 GJ cases, we identified four mutation carriers (31%); two in SDHC, one in SDHB, and one in SDHD. All patients with pathogenic mutations were of Hispanic ethnicity, presented at a younger age (mean 27.5 versus 52.11 years), and with more advanced disease when compared to mutation-negative GJ cases.Conclusions and Significance: Mutations in the SDH genes are found in 31% of sporadic GJ. SDH-associated GJ had advanced disease and a 50% risk of metastasis. Our data supports emerging recommendations for genetic screening in all populations with GJ tumours as the genetic status informs management.

Structure of the human respiratory complex II

Human complex II is a key protein complex that links two essential energy-producing processes: the tricarboxylic acid cycle and oxidative phosphorylation. Deficiencies due to mutagenesis have been shown to cause mitochondrial disease and some types of cancers. However, the structure of this complex is yet to be resolved, hindering a comprehensive understanding of the functional aspects of this molecular machine. Here, we have determined the structure of human complex II in the presence of ubiquinone at 2.86 Å resolution by cryoelectron microscopy, showing it comprises two water-soluble subunits, SDHA and SDHB, and two membrane-spanning subunits, SDHC and SDHD. This structure allows us to propose a route for electron transfer. In addition, clinically relevant mutations are mapped onto the structure. This mapping provides a molecular understanding to explain why these variants have the potential to produce disease.

Hereditary head and neck paraganglioma: from basics to practical consequences

PURPOSE OF REVIEW

This review summarizes practical recommendations for screening, work-up, and management of hereditary head and neck paragangliomas based on the growing molecular and empirical understanding of this disease.

RECENT FINDINGS

The proportion of hereditary cases among head and neck paragangliomas is significant (∼33 to 50%), and specific genetic alterations may increase the risk of malignancy. Genotyping should be performed for each case, and patients carrying a pathological mutation should be regularly screened for new tumors. Computed tomography (CT), magnetic resonance imaging (MRI), digital subtraction angiography (DSA), and functional positron emission tomography (PET) can provide a reliable preoperative diagnosis in the absence of histology. Comparative data on therapeutic outcome and morbidity now render radiation, stereotactic radiosurgery, and active surveillance preferable over surgery in highly advanced cases of jugulotympanic and vagal paragangliomas, whereas surgery remains the first choice for most carotid body paragangliomas.

SUMMARY

Complete paraganglioma removal continues to be the primary therapeutic goal; however, this is sometimes impossible to accomplish with acceptable morbidity. In these cases, therapy selection should focus on preserving cranial nerve function and minimizing both tumor-associated and therapy-associated complications, particularly in genetically predisposed patients. An interdisciplinary approach to the management of hereditary head and neck paragangliomas is strongly recommended.

Efficacy and Safety of Tyrosine Kinase Inhibitors in Patients with Metastatic Pheochromocytomas/Paragangliomas

CONTEXT

Tyrosine kinase inhibitors (TKIs) can be used to treat locally unresectable or distantly metastatic pheochromocytomas/paragangliomas (PPGLs), such as sunitinib, according to the National Comprehensive Cancer Network guidelines in 2022. However, the precise effect of different TKIs in metastatic PPGLs is still unclear.

OBJECTIVE

The aim of this meta-analysis is to assess the efficacy and safety of TKIs in metastatic PPGLs.

METHODS

The PubMed, Cochrane Library, Scopus, Clinical Trial, and Embase databases were searched by synonyms of 48 TKIs and metastatic PPGLs from inception up to August 2022. Outcomes were tumor response or survival data and the incidence of adverse events (AEs) after treatment. The MIONRS scale and the JBI's tools for case series were used for interventional and observational studies to assess risk of bias, respectively. The combined effects with fixed- or random-effect models, the combined median with the weighted median of medians method and their 95% CIs were reported.

RESULTS

A total of 7 studies with 160 patients were included. Tumor responses in metastatic PPGLs in 5 studies with available data showed the pooled proportion of partial response (PR), stable disease, and disease control rate (DCR) of, respectively, 0.320 (95% CI 0.155-0.486), 0.520 (95% CI 0.409-0.630), and 0.856 (95% CI 0.734-0.979). The combined median progressive-free survival in 6 studies was 8.9 months (95% CI 4.1-13.5) and the proportion of those who discontinued due to AEs in 5 studies was 0.143 (95% CI 0.077-0.209).

CONCLUSION

This meta-analysis suggests that patients with metastatic PPGLs can benefit from TKI therapy with PR and DCR up to more than 30% and 80%. However, because of restricted studies, larger clinical trials should be performed in the future.

SDHx mutation and pituitary adenoma: can in vivo 1H-MR spectroscopy unravel the link?

Germline mutations in genes encoding succinate dehydrogenase (SDH) are frequently involved in pheochromocytoma/paraganglioma (PPGL) development and were implicated in patients with the '3PAs' syndrome (associating pituitary adenoma (PA) and PPGL) or isolated PA. However, the causality link between SDHx mutation and PA remains difficult to establish, and in vivo tools for detecting hallmarks of SDH deficiency are scarce. Proton magnetic resonance spectroscopy (1H-MRS) can detect succinate in vivo as a biomarker of SDHx mutations in PGL. The objective of this study was to demonstrate the causality link between PA and SDH deficiency in vivo using 1H-MRS as a novel noninvasive tool for succinate detection in PA. Three SDHx-mutated patients suffering from a PPGL and a macroprolactinoma and one patient with an apparently sporadic non-functioning pituitary macroadenoma underwent MRI examination at 3 T. An optimized 1H-MRS semi-LASER sequence (TR = 2500 ms, TE = 144 ms) was employed for the detection of succinate in vivo. Succinate and choline-containing compounds were identified in the MR spectra as single resonances at 2.44 and 3.2 ppm, respectively. Choline compounds were detected in all the tumors (three PGL and four PAs), while a succinate peak was only observed in the three macroprolactinomas and the three PGL of SDHx-mutated patients, demonstrating SDH deficiency in these tumors. In conclusion, the detection of succinate by 1H-MRS as a hallmark of SDH deficiency in vivo is feasible in PA, laying the groundwork for a better understanding of the biological link between SDHx mutations and the development of these tumors.

Extraadrenal pheochromocytoma presenting with severe hematuria and postmicturition cephalgia, a case report of a rare bladder tumor entity

Paraganglioma (PGL) of the urinary bladder are a very rare tumor entity. Treatment of a PGL requires a multidisciplinary approach. We report on a case of a malignant pheochromocytoma (PHEO) of the bladder in a male adult due to a succinate dehydrogenase B (SDHB) subunit gene mutation where a partial cystectomy was perfomed after preoperative alpha blocking.

When a Multidisciplinary Approach Is Life-Saving: A Case Report of Cardiogenic Shock Induced by a Large Pheochromocytoma

BACKGROUND

Pheochromocytoma is known for its instantaneous presentation, especially in the younger population. Hemodynamic instability may be the cause of severe complications and impede patients' ability to undergo surgical treatment. These tumours are surgically difficult to treat due to the risk of catecholamine release during their manipulations, and when they are large, the tumour size represents an additional challenge. In our report, cardiogenic shock developed due to increases in systemic vascular resistance, and the lesion's size induced surgeons to perform open surgery.

CASE PRESENTATION

A 46-year-old female patient was admitted to our intensive care unit with hypertension and later cardiogenic shock. Systolic dysfunction was noted, along with severely increased systemic vascular resistance. A CT scan showed a left-sided 8.5 cm adrenal mass, which was confirmed as pheochromocytoma using meta-iodobenzylguanidine scintigraphy. Anaesthesiologists and the surgical team planned an effective strategy of treatment. Given the lesion's size and its apparent invasion of the neighbouring organs, open adrenalectomy (after prolonged hemodynamic stabilisation) was considered safer. The surgery was successful, and the patient remains free from disease two years after the initial event.

CONCLUSIONS

Large pheochromocytoma can be safely and effectively treated with open surgery by experienced hands but only by seeking to reach hemodynamic stabilisation and minimising the release of catecholamine before and during surgery.

Bilateral Pheochromocytoma with Germline MAX Variant without Family History

Recently, the genetic background of pheochromocytomas/paragangliomas (PPGLs) has been rapidly revealed. These tumors have been referred to as the “ten percent tumor”; however, the frequency of genetic variants of PPGLs has turned out to be more common than expected. PPGLs are potentially hereditary tumors and appear clinically sporadic. Here, we report a case of bilateral pheochromocytoma (PCC) with a variant in the MYC-associated factor X (MAX) gene (c.295 + 1G > A). A male patient was diagnosed with adrenal pheochromocytoma (PCC) and underwent a left adrenalectomy at the age of 40. A new tumor in the right adrenal gland was detected at the age of 43. Urinary metanephrine and normetanephrine concentrations gradually increased. The size of the right adrenal PCC continued to increase one year after detection. Genetic testing of the peripheral blood revealed the presence of a pathogenic variant in MAX. The natural history of adrenal PCCs with the MAX variant has not yet been clarified, because the number of reported cases is not sufficient. Thus, clinicians should consider a MAX variant when they find bilateral or multiple PCCs.

Head and Neck Paragangliomas: An Update on the Molecular Classification, State-of-the-Art Imaging, and Management Recommendations

Paragangliomas are neuroendocrine tumors that derive from paraganglia of the autonomic nervous system, with the majority of parasympathetic paragangliomas arising in the head and neck. More than one-third of all paragangliomas are hereditary, reflecting the strong genetic predisposition of these tumors. The molecular basis of paragangliomas has been investigated extensively in the past couple of decades, leading to the discovery of several molecular clusters and more than 20 well-characterized driver genes (somatic and hereditary), which are more than are known for any other endocrine tumor. Head and neck paragangliomas are largely related to the pseudohypoxia cluster and have been previously excluded from most molecular profiling studies. This review article introduces the molecular classification of paragangliomas, with a focus on head and neck paragangliomas, and discusses its impact on the management of these tumors. Genetic testing is now recommended for all patients with paragangliomas to provide screening and surveillance recommendations for patients and relatives. While CT and MRI provide excellent anatomic characterization of paragangliomas, gallium 68 tetraazacyclododecane tetraacetic acid-octreotate (ie, ⁶⁸Ga-DOTATATE) has superior sensitivity and is recommended as first-line imaging in patients with head and neck paragangliomas with concern for multifocal and metastatic disease, patients with known multifocal and metastatic disease, and in candidates for targeted peptide-receptor therapy. Keywords: Molecular Imaging, MR Perfusion, MR Spectroscopy, Neuro-Oncology, PET/CT, SPECT/CT, Head/Neck, Genetic Defects © RSNA, 2022.

Universal Germline Panel Testing for Individuals With Pheochromocytoma and Paraganglioma Produces High Diagnostic Yield

BACKGROUND

Practice guidelines to identify individuals with hereditary pheochromocytomas and paragangliomas (PPGLs) advocate for sequential gene testing strategy guided by specific clinical features and predate the routine use of multigene panel testing (MGPT).

OBJECTIVE

To describe results of MGPT for hereditary PPGL in a clinically and ancestrally diverse cohort.

SETTING

Commercial laboratory based in the United States.

METHODS

Clinical data and test results were retrospectively reviewed in 1727 individuals who had targeted MGPT from August 2013 through December 2019 because of a suspicion of hereditary PPGL.

RESULTS

Overall, 27.5% of individuals had a pathogenic or likely pathogenic variant (PV), 9.0% had a variant of uncertain significance, and 63.1% had a negative result. Most PVs were identified in SDHB (40.4%), followed by SDHD (21.1%), SDHA (10.1%), VHL (7.8%), SDHC (6.7%), RET (3.7%), and MAX (3.6%). PVs in FH, MEN1, NF1, SDHAF2, and TMEM127 collectively accounted for 6.5% of PVs. Clinical predictors of a PV included extra-adrenal location, early age of onset, multiple tumors, and positive family history of PPGL. Individuals with extra-adrenal PGL and a positive family history were the most likely to have a PV (85.9%). Restricting genetic testing to SDHB/C/D misses one-third (32.8%) of individuals with PVs.

CONCLUSION

Our data demonstrate a high diagnostic yield in individuals with and without established risk factors, a low inconclusive result rate, and a substantial contribution to diagnostic yield from rare genes. These findings support universal testing of all individuals with PPGL and the use of concurrent MGPT as the ideal platform.

SDHC phaeochromocytoma and paraganglioma: A UK-wide case series

OBJECTIVE

Phaeochromocytomas and paragangliomas (PPGL) are rare, but strongly heritable tumours. Variants in succinate dehydrogenase (SDH) subunits are identified in approximately 25% of cases. However, clinical and genetic information of patients with SDHC variants are underreported.

DESIGN

This retrospective case series collated data from 18 UK Genetics and Endocrinology departments.

PATIENTS

Both asymptomatic and disease-affected patients with confirmed SDHC germline variants are included.

MEASUREMENTS

Clinical data including tumour type and location, surveillance outcomes and interventions, SDHC genetic variant assessment, interpretation, and tumour risk calculation.

RESULTS

We report 91 SDHC cases, 46 probands and 45 non-probands. Fifty-one cases were disease-affected. Median age at genetic diagnosis was 43 years (range: 11-79). Twenty-four SDHC germline variants were identified including six novel variants. Head and neck paraganglioma (HNPGL, n = 30, 65.2%), extra-adrenal paraganglioma (EAPGL, n = 13, 28.2%) and phaeochromocytomas (PCC) (n = 3, 6.5%) were present. One case had multiple PPGLs. Malignant disease was reported in 19.6% (9/46). Eight cases had non-PPGL SDHC-associated tumours, six gastrointestinal stromal tumours (GIST) and two renal cell cancers (RCC). Cumulative tumour risk (95% CI) at age 60 years was 0.94 (CI: 0.79-0.99) in probands, and 0.16 (CI: 0-0.31) in non-probands, respectively.

CONCLUSIONS

This study describes the largest cohort of 91 SDHC patients worldwide. We confirm disease-affected SDHC variant cases develop isolated HNPGL disease in nearly 2/3 of patients, EAPGL and PCC in 1/3, with an increased risk of GIST and RCC. One fifth developed malignant disease, requiring comprehensive lifelong tumour screening and surveillance.

[Succinate dehydrogenase in cancer]

Succinate dehydrogenase (SDH) is a mitochondrial enzyme that participates in both the tricarboxylic acid cycle and the electron transport chain. Mutations in genes encoding SDH are responsible for a predisposition to pheochromocytomas and paragangliomas, and more rarely, to gastrointestinal stromal tumors or renal cell carcinomas. A decrease in SDH activity, not explained by genetics, has also been observed in more common cancers. One of the consequences of the inactivation of SDH is the excessive production of its substrate, succinate, which acts as an oncometabolite by promoting a pseudohypoxic status and an extensive epigenetic rearrangement. Understanding SDH-related oncogenesis now makes it possible to develop innovative diagnostic methods and to consider targeted therapies for the management of affected patients.

Case Report: Genetic Alterations Associated with the Progression of Carotid Paraganglioma

Paragangliomas (PGLs) are rare neuroendocrine tumors that can develop from any paraganglion across the body. The carotid body is the most often location of PGLs in the head and neck region. Carotid PGLs (CPGLs) are characterized by predominantly non-aggressive behavior; however, all tumors have the potential to metastasize. To date, molecular mechanisms of paraganglioma progression remain elusive. We report a case of a 38-year-old woman with metastatic CPGL manifesting as a recurrent tumor with lymph node metastasis. The tumor was fast-growing and had a high Ki-67 proliferation index. Immunohistochemical (IHC) examination and whole-exome sequencing were performed for both recurrent tumor and metastasis. A germline pathogenic splice acceptor variant in the SDHB gene was found in the patient. Immunoreactivity of the SDHB subunit was weak diffuse in both samples, indicating deficiency of the succinate dehydrogenase. Moreover, the recurrent tumor exhibited loss of heterozygosity (LOH) at the SDHB locus, that is according to Knudson's "two-hit" hypothesis of cancer causation. We also identified a rare somatic promotor mutation in the TERT gene associated with the tumor progression. Obtained results confirmed the indicative role of the germline SDHB mutation for metastatic CPGLs, as well as the potential prognostic value of the TERT promoter mutation.

Radiotherapy of benign intracranial tumours

We present the updated recommendations of the French Society for Radiation Oncology on benign intracranial tumours. Most of them are meningiomas, vestibular schwannomas, pituitary adenomas, craniopharyngiomas, and glomus tumours. Some grow very slowly, and can be observed without specific treatment, especially if they are asymptomatic. Symptomatic or growing tumours are treated by surgery, which is the reference treatment. When surgery is not possible, due to the location of the lesion, or general conditions, radiotherapy can be applied, as it is if there is a postoperative growing residual tumour, or a local relapse. Indications have to be discussed at a multidisciplinary panel, with precise evaluation of the benefit and risks of the treatments. The techniques to be used are the most modern ones, as multimodal imaging and image-guided radiation therapy. Stereotactic treatments, using fractionated or single doses depending on the size or the location of the tumours, are commonly realized, to avoid as much a possible the occurrence of late side effects.

Precision Medicine in Phaeochromocytoma and Paraganglioma

Precision medicine is a term used to describe medical care, which is specifically tailored to an individual patient or disease with the aim of ensuring the best clinical outcome whilst reducing the risk of adverse effects. Phaeochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumours with uncertain malignant potential. Over recent years, the molecular profiling of PPGLs has increased our understanding of the mechanisms that drive tumorigenesis. A high proportion of PPGLs are hereditary, with non-hereditary tumours commonly harbouring somatic mutations in known susceptibility genes. Through detailed interrogation of genotype-phenotype, correlations PPGLs can be classified into three different subgroups or clusters. Thus, PPGLs serve as an ideal paradigm for developing, testing and implementing precision medicine concepts in the clinic. In this review, we provide an overview of PPGLs and highlight how detailed molecular characterisation of these tumours provides current and future opportunities for precision oncology.

[Clinical and laboratory features of hereditary pheochromocytoma and paraganglioma]

The widespread introduction of genetic testing in recent years has made it possible to determine that more than a third of cases of pheochromocytomas and paragangliomas (PPPGs) are caused by germline mutations. Despite the variety of catecholamine-producing tumors manifestations, there is a sufficient number of clinical and laboratory landmarks that suggest a hereditary genesis of the disease and even a specific syndrome. These include a family history, age of patient, presence of concomitant conditions, and symptoms of the disease. Considering that each of the mutations is associated with certain diseases that often determine tactics of treatment and examination of a patient, e.g. high risk of various malignancies. Awareness of the practitioner on the peculiarities of the course of family forms of PPPGs will allow improving the tactics of managing these patients.The article provides up-to-date information on the prevalence of hereditary PPPGs. The modern views on the pathogenesis of the disease induced by different mutations are presented. The main hereditary syndromes associated with PPPGs are described, including multiple endocrine neoplasia syndrome type 2A and 2B, type 1 neurofibromatosis, von Hippel-Lindau syndrome, hereditary paraganglioma syndrome, as well as clinical and laboratory features of the tumor in these conditions. The main positions on the necessity of genetic screening in patients with PPPGs are given.

Potential Biomarkers of Metastasizing Paragangliomas and Pheochromocytomas

Paragangliomas and pheochromocytomas (PPGLs) are rare neuroendocrine tumors originating from paraganglionic tissue in many sites of the body. Most PPGLs are characterized by nonaggressive behavior but all of them have the potential to metastasize. PPGLs represent a great diagnostic dilemma as it is difficult to recognize tumors that are likely to be metastasizing; criteria of malignancy can be found both in benign and metastatic forms. This review aims to analyze the current knowledge of the nature of metastasizing PPGLs paying particular attention to head and neck paragangliomas (HNPGLs). Potential predictors of the malignancy risk for PPGLs were summarized and discussed. These data may also help in the development of diagnostic and prognostic strategies, as well as in the identification of novel potential therapeutic targets for patients with PPGLs.

The Influence of Young Age on Difficulties in the Surgical Resection of Carotid Body Tumors

Simple Summary

The aim of this study was to reveal the factors affecting the complexity and difficulties in performing surgery to resect carotid body tumors (CBTs). We analyzed 20 patients with 21 CBTs. We used the “same day surgery” procedure, including preoperative embolization of the feeding arteries in the morning and resection surgery in the afternoon of the same day. Four patients underwent resection of the carotid artery, followed by reconstruction. These four patients were between 18 to 23 years of age at the time of surgery. The mean blood loss and operative time in these patients differed significantly from those in older patients. These results indicated that young age may influence the difficulties faced in CBT surgery, resulting in an increased risk of carotid artery resection. The results obtained from our study could help surgeons safely and effectively perform resection surgery for CBTs.

Abstract

This study evaluated patient characteristics that affect the complexity and difficulties of performing surgery to resect carotid body tumors (CBTs). We retrospectively reviewed the medical records of 20 patients with 21 CBTs who were enrolled in the study. The median patient age was 46 years and the mean tumor diameter was 37.6 mm. The mean blood loss and operative time were 40.3 mL and 183 min, respectively. Four patients underwent resection of the carotid artery followed by reconstruction. These four patients were between 18 to 23 years of age at the time of surgery. The mean blood loss and operative time in these patients were 166 mL and 394 min, respectively, which differed significantly from those of older patients. Therefore, young age influenced the difficulties faced in surgical resection of CBT, with an increased risk of blood loss and carotid artery resection.

International initiative for a curated SDHB variant database improving the diagnosis of hereditary paraganglioma and pheochromocytoma

BACKGROUND

SDHB is one of the major genes predisposing to paraganglioma/pheochromocytoma (PPGL). Identifying pathogenic SDHB variants in patients with PPGL is essential to the management of patients and relatives due to the increased risk of recurrences, metastases and the emergence of non-PPGL tumours. In this context, the 'NGS and PPGL (NGSnPPGL) Study Group' initiated an international effort to collect, annotate and classify SDHB variants and to provide an accurate, expert-curated and freely available SDHB variant database.

METHODS

A total of 223 distinct SDHB variants from 737 patients were collected worldwide. Using multiple criteria, each variant was first classified according to a 5-tier grouping based on American College of Medical Genetics and NGSnPPGL standardised recommendations and was then manually reviewed by a panel of experts in the field.

RESULTS

This multistep process resulted in 23 benign/likely benign, 149 pathogenic/likely pathogenic variants and 51 variants of unknown significance (VUS). Expert curation reduced by half the number of variants initially classified as VUS. Variant classifications are publicly accessible via the Leiden Open Variation Database system (https://databases.lovd.nl/shared/genes/SDHB).

CONCLUSION

This international initiative by a panel of experts allowed us to establish a consensus classification for 223 SDHB variants that should be used as a routine tool by geneticists in charge of PPGL laboratory diagnosis. This accurate classification of SDHB genetic variants will help to clarify the diagnosis of hereditary PPGL and to improve the clinical care of patients and relatives with PPGL.

Familial SDHB gene mutation in disseminated non-hypoxia-related malignant paraganglioma treated with [90Y]Y/[177Lu]Lu- DOTATATE

Familial paraganglioma may be related to mutations in succinate dehydrogenase (SDH) enzyme complex genes. Among patients with hereditary paraganglioma, SDH subunit B (SDHB) gene mutations are associated with the highest morbidity and mortality related to a higher malignancy rate. We report a family with the c.689G>A (p.Arg230His) mutation in the SDHB gene identified in two family members, a father and his daughter. While the 14-year-old daughter had no evidence of clinical disease, recurrent and later disseminated [¹³¹I]metaiodobenzylguanidine uptake-negative head and neck paraganglioma with multiple bone metastases developed in the father who underwent peptide receptor radionuclide therapy with [⁹⁰Y]Y/[¹⁷⁷Lu]Lu-dodecane tetraacetic acid octreotate (DOTATATE) at the time of the genetic diagnosis. This treatment was repeated 6 years later due to disease progression and the patient, who is currently 49 years old, remains alive and in good overall clinical condition at 8 years of follow-up after the original presentation at our unit. The growing armamentarium of imaging methods available for such patients may inform decision making regarding choice of the optimal treatment approach, potentially contributing to improved outcomes.

FDG PET-CT imaging in head and neck paragangliomas: A centre experience

Head and neck paragangliomas (HNPGLs) are rare tumours with ~ 30% genetic mutations, mainly in succinate dehydrogenase (SDHx) genes. The utility of FDG PET-CT in HNPGLs is questioned by recent developments in novel radiotracers. We therefore performed a retrospective study in a single tertiary referral centre to address the utility of FDG PET/CT in HNPGLs.

METHODS

Clinical data on genetic testing and follow-up were collected for patients who had FDG PET-CT scans from 2004 to 2016. Receiver operator characteristic (ROC) analysis was used to compare standardized uptake values (SUVs), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) between lesions in patients who had a clinically related event: event (+) and those who did not: event (-). Similarly, we compared PET parameters between SDHx+ patients and a control group with low probability of mutation.

RESULTS

Of 153 HNPGL patients, 73 (29 SDHx+) with 93 FDG-positive lesions were identified: 53.8% of lesions were assessed in a pre-therapeutic setting. In comparison with a reference extracted from clinicoradiological database, FDG PET-CT showed good performance to detect HNPGLs (96.6% accuracy). In this study population, 16 disease progression, 1 recurrence and 1 death were recorded and event (+) patients had lesions with higher SUVmax (p = .03 and p = .02, respectively). Conversely, there were no differences in PET parameters between lesions in SDHx+ patients and controls with low probability of SDHx+ mutations.

CONCLUSIONS

FDG PET-CT has clinical utility in HNPGLs, mostly before local treatment. There were no significant differences in PET parameters between SDHx patients and a sporadic HNPGL population. However, regardless of SDHx mutation status, a high SUVmax was associated with more clinical events and prompts to a closer follow-up.

International consensus on initial screening and follow-up of asymptomatic SDHx mutation carriers

Approximately 20% of patients diagnosed with a phaeochromocytoma or paraganglioma carry a germline mutation in one of the succinate dehydrogenase (SDHx) genes (SDHA, SDHB, SDHC and SDHD), which encode the four subunits of the SDH enzyme. When a pathogenic SDHx mutation is identified in an affected patient, genetic counselling is proposed for first-degree relatives. Optimal initial evaluation and follow-up of people who are asymptomatic but might carry SDHx mutations have not yet been agreed. Thus, we established an international consensus algorithm of clinical, biochemical and imaging screening at diagnosis and during surveillance for both adults and children. An international panel of 29 experts from 12 countries was assembled, and the Delphi method was used to reach a consensus on 41 statements. This Consensus Statement covers a range of topics, including age of first genetic testing, appropriate biochemical and imaging tests for initial tumour screening and follow-up, screening for rare SDHx-related tumours and management of elderly people who have an SDHx mutation. This Consensus Statement focuses on the management of asymptomatic SDHx mutation carriers and provides clinicians with much-needed guidance. The standardization of practice will enable prospective studies in the near future.

Genetic Variants in Patients with Multiple Head and Neck Paragangliomas: Dilemma in Management

Multiple head and neck paragangliomas (HNPGLs) are neuroendocrine tumors of a mostly benign nature that can be associated with a syndrome, precipitated by the presence of a germline mutation. Familial forms of the disease are usually seen with mutations of SDHx genes, especially the SDHD gene. SDHB mutations are predisposed to malignant tumors. We found 6 patients with multiple tumors amongst 30 patients with HNPGLs during the period of 2016 to 2021. We discuss the phenotypic and genetic patterns in our patients with multiple HNPGLs and explore the management possibilities related to the disease. Fifty percent of our patients had incidental findings of HNPGLs. Twenty-one biochemically silent tumors were found. Four patients had germline mutations, and only one had a positive family history. Three out of five underwent surgery without permanent complications. Preventative measures (genetic counselling and tumor surveillance) represent the gold standard in effectively controlling the disease in index patients and their relatives. In terms of treatment, apart from surgical and radiotherapeutic interventions, new therapeutic measures such as gene targeted therapy have contributed very sparsely. With the lack of standardized protocols, management of patients with multiple HNPGLs still remains very challenging, especially in those with sporadic or malignant forms of the disease.

Incomplete penetrance of a novel SDHD variation causing familial head and neck paraganglioma

Objective

Identification of variations in tumour suppressor genes encoding the tetrameric succinate dehydrogenase (SDHx) mitochondrial enzyme complex may lead to personalised therapeutic concepts for the orphan disease, familial paraganglioma (PGL) type 1‐5. We undertook to determine the causative variation in a family suffering from idiopathic early‐onset (22 ± 2 years) head and neck PGL by PCR and Sanger sequencing.

Design

Prospective genetic study.

Setting

Tertiary Referral Otolaryngology Centre.

Participants

Twelve family members.

Main outcome measures

Main outcomes were clinical analysis and SDH genotyping

Results and Conclusions

A novel heterozygous c.298delA frameshift variation in exon 3 of SDH subunit D (SDHD) was associated with a paternal transmission pattern of PGL in affected family members available to the study. Family history over five generations in adulthood indicated a variable penetrance for PGL inheritance in older generations. The c.298delA variant would cause translation of a 34‐residue C‐terminus distal to lysine residue 99 in the predicted transmembrane domain II of the full‐length sequence p.(Thr100LeufsTer35) and would affect the translation products of all protein‐coding SDHD isoforms containing transmembrane topologies required for positional integration in the inner mitochondrial membrane and complex formation. These results underly the importance of genetic screening for PGL also in cases of unclear inheritance, and variation carriers should benefit from screening and lifelong follow‐up.

Helping young children understand inherited cancer predisposition syndromes using bibliotherapy

Communication with children about hereditary conditions in the family can be difficult for parents. Yet, good communication strategies are leading determinants of adaptation and resilience. With inherited cancer predisposition syndromes that can affect young children such as Li-Fraumeni syndrome (LFS) and hereditary pheochromocytoma and paraganglioma syndrome (HPPS), genetic testing and subsequent surveillance in at-risk children is the optimal intervention. Given testing often commences early, providing children and their parents with appropriate genetic counseling and communication strategies is important for informed decision making. To inform such communication strategies, we used a bibliotherapeutic framework, where stories are delivered prescriptively (i.e., 'bibliotherapy'), to develop a psycho-educational resource for children aged 5-10 years old at risk of either LFS or HPPS. Illustrated storybooks for children were created based on models of developmental comprehension. To ascertain their experience, parents were invited to read a storybook to their child/ren and participate in semi-structured qualitative interviews. Transcripts were analyzed thematically using a general inductive approach. The bibliotherapeutic resource reportedly supported parents with communication about these issues without raising emotional distress in either themselves or their children. The key stages of a bibliotherapeutic interaction were facilitated by the use of this resource, and all parents reported that it would have been useful when their children were first tested and/or diagnosed. This study lays the foundation for the application of bibliotherapy as a psycho-educational intervention in genetic counseling and demonstrates that bibliotherapy may improve the process of communication between parents and children regarding pediatric-inherited cancer syndromes.

Head and Neck Paragangliomas: Patterns of Otolaryngology Referrals for Genetic Testing Over 2 Decades

Objective

A large proportion of head and neck paragangliomas (HNPGLs) arise in patients with a genetic predisposition due to pathogenic variants in succinate dehydrogenase (SDHx) genes. Contemporary practice guidelines recommend consideration of referral for genetic testing for all patients with HNPGLs. We sought to assess adherence to these recommendations, factors associated with referral, and temporal trends in referral patterns by otolaryngologists over the past 2 decades.

Study Design

Retrospective cohort study.

Setting

Single tertiary care center.

Methods

All patients with newly diagnosed HNPGLs treated at a single academic center between 2000 and 2019 were included. Bivariable association of specific features of referral for genetic testing by treating surgeons were tested with χ² and Wilcoxon rank-sum tests. Logistic regression was used to assess temporal trends in referral patterns overall and for specific clinical subgroups over time.

Results

Of 221 patients included, only 77 (34.8%) were referred for genetic testing. Factors associated with referral included young age, family history of paraganglioma, more recent year of diagnosis (ie, closer to study end date), tumor subsite (all P < .0001), and treatment by an otolaryngologist (vs vascular surgeon or neurosurgeon, P = .009). Overall, referral rates increased over time (P = .0002), but even in the most recent 5 years, only 51% of newly diagnosed patients were referred.

Conclusion

Our analysis suggests that referral rates for genetic testing in patients with HNPGLs are growing yet are still largely based on young age, family history, and tumor subsite.

What Have We Learned from Molecular Biology of Paragangliomas and Pheochromocytomas?

Recent advances in molecular genetics and genomics have led to increased understanding of the aetiopathogenesis of pheochromocytomas and paragangliomas (PPGLs). Thus, pan-genomic studies now provide a comprehensive integrated genomic analysis of PPGLs into distinct molecularly defined subtypes concordant with tumour genotypes. In addition, new embryological discoveries have refined the concept of how normal paraganglia develop, potentially establishing a developmental basis for genotype-phenotype correlations for PPGLs. The challenge for modern pathology is to translate these scientific discoveries into routine practice, which will be based largely on histopathology for the foreseeable future. Here, we review recent progress concerning the cell of origin and molecular pathogenesis of PPGLs, including pathogenetic mechanisms, genetic susceptibility and molecular classification. The current roles and tools of pathologists are considered from a histopathological perspective, including differential diagnoses, genotype-phenotype correlations and the use of immunohistochemistry in identifying hereditary predisposition and validating genetic variants of unknown significance. Current and potential molecular prognosticators are also presented with the hope that predictive molecular biomarkers will be integrated into risk stratification scoring systems to assess the metastatic potential of these intriguing neoplasms and identify potential drug targets.

Hereditary Paraganglioma in an Omani Family

Pheochromocytomas are tumors derived from chromaffin cells within the medulla of adrenal glands, whereas paragangliomas are tumors derived from extra-adrenal chromaffin cells of the sympathetic prevertebral and paravertebral ganglia. The growing deployment of genetic testing has shown that approximately 30% of pheochromocytoma and paraganglioma (PPGL) patients carry familial pathogenic germline mutations in known PPGL-susceptibility genes. This prompts genetic screening of their family members and leads to an increase in the detection of asymptomatic PPGLs or non-secreting tumors reported in familial cases discovered after the index patient work-up. Here, we present three case reports of affected members of a single Omani family with a history of paraganglioma and highly variable clinical presentations among the affected members. Eight out of the 16 siblings (50.0%) in the second generation of the reported family pedigree were carriers of the succinate dehydrogenase B:c.574T>C mutation, reflecting the autosomal dominant inheritance risk of paraganglioma and other associated tumors. This report highlights the complexity of managing such families and encourages further discussion regarding the management of asymptomatic PPGL-associated mutation carriers. Genetic screening has enabled the early detection of PPGLs, for which early surgical intervention can significantly impact prognosis and treatment strategies to reduce morbidity and mortality. Although PPGLs are similar tumors, they warrant distinction from each other with respect to their differences in locations, manifestations, secretory functions, genetic syndromes, and propensity to metastasize. While current guidelines are clear concerning symptomatic PPGL cases, the management of asymptomatic mutation carriers requires further elucidation.

Radiation-Induced Malignant Peripheral Nerve Sheath Tumor of the Vagus Nerve Following Radiation Treatment of Cervical Paraganglioma

Radiation-induced sarcoma is a known but rare complication of radiation treatment for skull base paraganglioma. We present the cases of a female patient with multiple paraganglioma syndrome treated with external beam radiation treatment who presented 4 years later with a malignant peripheral nerve sheath tumor of the vagus nerve.

Characteristics and genetic testing outcomes of patients with clinically suspected paraganglioma/pheochromocytoma (PGL/PCC) syndrome in Singapore

BACKGROUND

Hereditary paraganglioma (PGL) and pheochromocytoma (PCC) syndromes are rare conditions, with limited data on spectrum of causative gene variants of these syndromes in Asian patients.

METHODS

We describe the clinical characteristics and genetic testing outcomes of patients with suspected hereditary PGL/PCC who were referred to a tertiary cancer genetics clinic in Singapore.

RESULTS

Among 2196 patients with suspected hereditary cancer syndrome evaluated at the cancer genetics clinic from 2000 to 2019, 13/2196 (0.6%) patients fulfilled clinical suspicion for hereditary PGL/PCC syndrome. After genetic counselling, 10 patients underwent multi-gene next generation sequencing and deletion/duplication analysis, including SDHAF2, SDHA, SDHB, SDHC, SDHD, VHL, NF1, RET, MAX, and TMEM127. Seven of 10 patients (70%) were identified to carry pathogenic variants, including 3 unrelated Chinese patients with head and neck PGL who carried the same SDHD: c.3G > C (p.Met1Ile) variant that was previously reported to be a possible founder variant in Chinese, and 3 patients with urogenital PGL and 1 patient with retroperitoneal PGL who carried different SDHB variants. Variant carriers were younger, more likely to present with multiple tumours, or have family history of paraganglioma or pheochromocytoma, than non- variant carriers.

CONCLUSION

Hereditary PGL/PCC accounts for only 0.6% of patients seen in an adult cancer genetics clinic in Asia. SDHD and SDHB genes remain the most important causative genes of hereditary PGL/PCC in Asia even when patients are tested with multi-gene NGS panel.

Systemic treatment of a metastatic carotid body tumor: A case report and literature review

RATIONALE

Carotid body tumors (CBTs) are head and neck paragangliomas (PGLs) with a low incidence of distant metastasis. To date, only a few metastatic cases treated with detailed systemic therapy are reported and effective management is still inconclusive. Herein, we reported a metastatic CBT case with systemic therapy and reviewed the reported systemic treatment.

PATIENT CONCERNS

A 56-year-old man noticed multiple painless nodules on the right side of the neck and developed debilitating chest and back pain 7 years after the CBT resection.

DIAGNOSES

Widespread bone and lymph nodes CBT metastases.

INTERVENTIONS

Biopsies of the enlarged lymph nodes confirmed the diagnosis of metastatic CBT and 18F-FDG PET-CT detected multiple right cervical lymph nodes and bone metastases. 24 cycles of cyclophosphamide, vincristine and dacarbazine (CVD) chemotherapy were given since May 2016 to Jul 2018 and dacarbazine maintenance therapy was given in the next 15 months follow-up period.

OUTCOMES

Partial remission was achieved according to the Response Evaluation in Criteria in Solid Tumors 1.1 criteria. A prominent control in the metastatic lesions were also observed in 18F-FDG PET-CT scan.

LESSONS

Evidence for systemic management of metastatic CBTs is mainly based on studies of PGLs and pheochromocytoma. According to our review on metastatic CBT cases treated with systemic therapy from 1981 to 2018, chemotherapy, especially the CVD regimen, was a common reported management. In SDHB mutated patients, sunitinib and temozolomide could also be considered.

Head and Neck Paragangliomas-A Genetic Overview

Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors. Head and neck paragangliomas (HNPGL) can be categorized into carotid body tumors, which are the most common, as well as jugular, tympanic, and vagal paraganglioma. A review of the current literature was conducted to consolidate knowledge concerning PGL mutations, familial occurrence, and the practical application of this information. Available scientific databases were searched using the keywords head and neck paraganglioma and genetics, and 274 articles in PubMed and 1183 in ScienceDirect were found. From these articles, those concerning genetic changes in HNPGLs were selected. The aim of this review is to describe the known genetic changes and their practical applications. We found that the etiology of the tumors in question is based on genetic changes in the form of either germinal or somatic mutations. 40% of PCC and PGL have a predisposing germline mutation (including VHL, SDHB, SDHD, RET, NF1, THEM127, MAX, SDHC, SDHA, SDHAF2, HIF2A, HRAS, KIF1B, PHD2, and FH). Approximately 25–30% of cases are due to somatic mutations, such as RET, VHL, NF1, MAX, and HIF2A. The tumors were divided into three main clusters by the Cancer Genome Atlas (TCGA); namely, the pseudohypoxia group, the Wnt signaling group, and the kinase signaling group. The review also discusses genetic syndromes, epigenetic changes, and new testing technologies such as next-generation sequencing (NGS).

The SDHB Arg230His mutation causing familial paraganglioma alters glycolysis in a new Caenorhabditis elegans model

The conserved B-subunit of succinate dehydrogenase (SDH) participates in the tricarboxylic acid cycle (TCA) cycle and mitochondrial electron transport. The Arg230His mutation in SDHB causes heritable pheochromocytoma/paraganglioma (PPGL). In Caenorhabditiselegans, we generated an in vivo PPGL model (SDHB-1 Arg244His; equivalent to human Arg230His), which manifests delayed development, shortened lifespan, attenuated ATP production and reduced mitochondrial number. Although succinate is elevated in both missense and null sdhb-1(gk165) mutants, transcriptomic comparison suggests very different causal mechanisms that are supported by metabolic analysis, whereby only Arg244His (not null) worms demonstrate elevated lactate/pyruvate levels, pointing to a missense-induced, Warburg-like aberrant glycolysis. In silico predictions of the SDHA-B dimer structure demonstrate that Arg230His modifies the catalytic cleft despite the latter's remoteness from the mutation site. We hypothesize that the Arg230His SDHB mutation rewires metabolism, reminiscent of metabolic reprogramming in cancer. Our tractable model provides a novel tool to investigate the metastatic propensity of this familial cancer and our approach could illuminate wider SDH pathology.This article has an associated First Person interview with the first author of the paper.

Mutation profiling in eight cases of vagal paragangliomas

Background

Vagal paragangliomas (VPGLs) belong to a group of rare head and neck neuroendocrine tumors. VPGLs arise from the vagus nerve and are less common than carotid paragangliomas. Both diagnostics and therapy of the tumors raise significant challenges. Besides, the genetic and molecular mechanisms behind VPGL pathogenesis are poorly understood.

Methods

The collection of VPGLs obtained from 8 patients of Russian population was used in the study. Exome library preparation and high-throughput sequencing of VPGLs were performed using an Illumina technology.

Results

Based on exome analysis, we identified pathogenic/likely pathogenic variants of the SDHx genes, frequently mutated in paragangliomas/pheochromocytomas. SDHB variants were found in three patients, whereas SDHD was mutated in two cases. Moreover, likely pathogenic missense variants were also detected in SDHAF3 and SDHAF4 genes encoding for assembly factors for the succinate dehydrogenase (SDH) complex. In a patient, we found a novel variant of the IDH2 gene that was predicted as pathogenic by a series of algorithms used (such as SIFT, PolyPhen2, FATHMM, MutationTaster, and LRT). Additionally, pathogenic/likely pathogenic variants were determined for several genes, including novel genes and some genes previously reported as associated with different types of tumors.

Conclusions

Results indicate a high heterogeneity among VPGLs, however, it seems that driver events in most cases are associated with mutations in the SDHx genes and SDH assembly factor-coding genes that lead to disruptions in the SDH complex.

Multiple paragangliomas: a case report

Background

Carotid and vagal paragangliomas (CPGLs and VPGLs) are rare neoplasms that arise from the paraganglia located at the bifurcation of carotid arteries and vagal trunk, respectively. Both tumors can occur jointly as multiple paragangliomas accounting for approximately 10 to 20% of all head and neck paragangliomas. However, molecular and genetic mechanisms underlying the pathogenesis of multiple paragangliomas remain elusive.

Case presentation

We report a case of multiple paragangliomas in a patient, manifesting as bilateral CPGL and unilateral VPGL. Tumors were revealed via computed tomography and ultrasound study and were resected in two subsequent surgeries. Both CPGLs and VPGL were subjected to immunostaining for succinate dehydrogenase (SDH) subunits and exome analysis. A likely pathogenic germline variant in the SDHD gene was indicated, while likely pathogenic somatic variants differed among the tumors.

Conclusions

The identified germline variant in the SDHD gene seems to be a driver in the development of multiple paragangliomas. However, different spectra of somatic variants identified in each tumor indicate individual molecular mechanisms underlying their pathogenesis.

Case of functioning thoracic paraganglioma

Functioning thoracic paraganglioma (PGL) is rare in clinical practice. We present a 33-year-old man with this pathology, who came with right-sided chest pain and was found to have a right-sided paravertebral mass. Fine needle aspiration cytology revealed a PGL. Urine normetanephrine was elevated and meta- iodobenzylguanidine scan showed increased tracer uptake in the right hemithorax, suggestive of a functioning neuroendocrine tumour. The patient was subjected to right PGL excision by video-assisted thoracoscopic surgery, after adequate preoperative preparations. The perioperative period was uneventful, except for a transient rise in blood pressure during the surgery. His blood pressure continued to be normal in the postoperative period. In any patient with a paravertebral mass, the possibility of PGL should be kept in mind even if the patient is normotensive. Making a preoperative diagnosis is important, because excision of functioning PGL without adequate preoperative preparation may be detrimental.

The genetic basis of isolated mitochondrial complex II deficiency

Mitochondrial complex II (succinate:ubiquinone oxidoreductase) is the smallest complex of the oxidative phosphorylation system, a tetramer of just 140 kDa. Despite its diminutive size, it is a key complex in two coupled metabolic pathways - it oxidises succinate to fumarate in the tricarboxylic acid cycle and the electrons are used to reduce FAD to FADH₂, ultimately reducing ubiquinone to ubiquinol in the respiratory chain. The biogenesis and assembly of complex II is facilitated by four ancillary proteins, all of which are autosomally-encoded. Numerous pathogenic defects have been reported which describe two broad clinical manifestations, either susceptibility to cancer in the case of single, heterozygous germline variants, or a mitochondrial disease presentation, almost exclusively due to bi-allelic recessive variants and associated with an isolated complex II deficiency. Here we present a compendium of pathogenic gene variants that have been documented in the literature in patients with an isolated mitochondrial complex II deficiency. To date, 61 patients are described, harbouring 32 different pathogenic variants in four distinct complex II genes: three structural subunit genes (SDHA, SDHB and SDHD) and one assembly factor gene (SDHAF1). Many pathogenic variants result in a null allele due to nonsense, frameshift or splicing defects however, the missense variants that do occur tend to induce substitutions at highly conserved residues in regions of the proteins that are critical for binding to other subunits or substrates. There is phenotypic heterogeneity associated with defects in each complex II gene, similar to other mitochondrial diseases.

Succinate dehydrogenase-deficient gastrointestinal stromal tumor of stomach diagnosed by endoscopic ultrasound-guided fine-needle biopsy: Report of a distinct subtype in cytology

Succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumors (GISTs) are characterized by the lack of mutations in KIT receptor tyrosine kinase complex and platelet derived growth factor receptor-alpha (PDGFRA) that are commonly found in the majority of GISTs. SDH-deficient GISTs comprise approximately 5%-10% of all GISTs. This subset may be associated with Carney Triad and Carney-Stratakis syndrome. SDH-deficient GISTs show unique demographic, radiologic, morphologic findings, clinical behavior, and treatment response. To our knowledge, the identification and characterization of this subset of GISTs have not yet been described in the cytopathology literature. By understanding the clinical as well as the other unique features of this tumor, in addition to the rapidly evolving identification of specific molecular alterations and targeted therapies, cytopathologists may play an important role in the diagnosis and work-up of these patients to allow clinicians to better manage and treat them. We present a young female with gastric SDH-deficient GIST diagnosed by fine-needle biopsy with supporting surgical pathology follow-up and molecular confirmation. This report suggests that the diagnosis of SDH-deficient GIST can be made on cytology in the appropriate clinical setting by using cytomorphologic features and demonstrating SDH loss by IHC on the cell block. In addition, molecular testing may be possible on the cytology cell block or supernatant to confirm the diagnosis.

Clinical Outcome of Carotid Body Paraganglioma Management: A Review of 10-Year Experience

Background

Carotid body paragangliomas are rare neoplasms usually benign, however sometimes presenting as highly aggressive tumors. Surgery is the main line of treatment.

Purpose

To study and describe clinical presentations, surgical approaches, postoperative complications, and treatment outcomes.

Materials and Methods

A single-institution retrospective analysis of 19 cases with carotid body paragangliomas who were candidates for surgery from January 2009 through January 2019 with a mean follow-up period of 58.8 months.

Results

The mean age was 46 years with the female predominance of 63%. The mean size of the tumor was 4.3 cm. All cases were presented with a painless pulsating neck lump located anteriorly at the level of the hyoid bone. Neck US was done in all cases as a primary screening investigation. CT scanning was the second main investigation performed in 17 cases (89.5%) revealing tumors attached to the carotid artery at its bifurcation. Urinary catecholamine metabolites were measured in all cases to rule out familial functioning types. 5 cases (26.3%) were malignant. All cases were surgically approached through transcervical transverse incision. 11, 5, and 3 cases were classified as Shamblin's type II, III, and I, respectively. All tumors were R0 resected with nodal neck dissection conducted in the malignant group. Major complications occurred in 4 cases (21%) during tumor dissection from the adventitia of carotid bifurcation. ECA ligation was performed in one case (5.3%). 2 patients (10.5%) suffered XII nerve paralysis. Carotid artery blowout occurred in one patient (5.3%) and was immediately controlled. No operative mortality occurred. All patients were free of disease during the follow-up period. 4 malignant cases (21%) suffered a systemic relapse to bone and lung metastasis justifying adjuvant chemotherapy, radiotherapy, or both.

Conclusions

Surgery is the treatment of choice for carotid body paragangliomas. Complete R0 resection should be justified especially in case of malignancy. Adjuvant chemotherapy or radiotherapy is an option for patients with primary malignancy or relapse.

A study of Titanium and Magnesium particle-induced oxidative stress and toxicity to human osteoblasts

Hybrid implants combine both Titanium (Ti) and Magnesium (Mg) are prevalent nowadays. The long-term implications of Ti and Mg implants within the human body are not yet fully understood. Many implant failure cases due to inflammation, allergic responses, and aspect loosening have been reported frequently. Particles generated through daily wear and tear of implants may worsen the situation by causing acute complications. An in-depth understanding of the behavior of metal particles with human osteoblasts is necessary. In this study, a novel and systematic attempt was made to understand the effects of different concentrations of Ti and Mg particles to the osteoblastic SAOS2 cell: toxicity, alterations to mitochondria, and changes to the specific gene and protein expression. Ti particles were found toxic to SAOS2 cells at different dosages, while Mg particles at lower concentrations could improve cell viability. To understand this phenomenon better, we have measured cellular reactive oxygen species (ROS) production and cell apoptosis & necrosis percentage. We also have checked the mitochondrial structure with transmission electron microscope (TEM), and mitochondrial function using Tetramethyl rhodamine, ethyl ester staining (TMRE). NDUFB6, SDHC, and ATP5F1 were the essential mitochondrial genes involved in the ROS production and ATP production. Immunocytochemistry (ICC) and real-time polymerase chain reaction (qPCR) were implemented to check the regulations of these related genes.

A SERIES OF TWO PATIENTS WITH CARDIAC PARAGANGLIOMAS

Objective

The objective of this report is to present 2 cases of cardiac paragangliomas (PGLs), and to outline the presentation, management, and associated genetic mutations.

Methods

Case 1, a 38-year-old female, presented with a 12-month history of paroxysmal palpitations, headaches, and weight loss. Her investigations included plasma free metanephrines and urinary metanephrines, 68-gallium DOTATATE positron emission tomography/computed tomography, and cardiac imaging. Case 2, a 28-year-old male, presented with a hypertensive crisis and abdominal pain on a background of hypertension. Given his abdominal pain, he was investigated with an abdominal computed tomography (CT) scan, followed by plasma free meta-nephrines and urinary metanephrines, echocardiogram, and 123-iodine meta-iodobenzylguanidine single-photon emission CT.

Results

Case 1 had an elevated plasma normetadrenaline of 6,750 pmol/L (reference range is <900 pmol/L) and 3-methoxytyramine of 1,845 pmol/L (reference range is <110 pmol/L). 68-gallium DOTATATE positron emission tomography/computed tomography showed an avid cardiac lesion. The lesion was resected, and histopathology confirmed PGL. Genetic studies revealed an SDHC gene mutation. For case 2, abdominal CT revealed a para-spinal mass. Workup for this lesion revealed elevated normetadrenaline of 56,000 pmol/L (reference range is <900 pmol/L). An echocardiogram, arranged for investigation of hypertension, showed an additional cardiac mass. A 123-iodine meta-iodobenzylguanidine single-photon emission CT scan confirmed that both masses were functioning. The lesions were successfully excised. He was found to have an SDHB gene mutation.

Conclusion

Both patients had long-standing symptoms secondary to catecholamine excess, thus it is important to promptly screen patients with unexplained hypertension or paroxysmal symptoms of palpitations, headaches, and diaphoresis with plasma free metanephrines or urinary metanephrines. All patients with PGLs should be offered genetic testing due to the high incidence of genetic mutations.

Genetic screening for monogenic hypertension in hypertensive individuals in a clinical setting

BACKGROUND

Monogenic hypertension describe a series of hypertensive syndromes that are inherited by Mendelian laws. Sometimes genetic testing is required to provide evidence for their diagnoses, precise classification and targeted treatment. This study is the first to investigate the clinical utility of a causative gene screening and the combined yield of gene product expression analyses in cases with suspected monogenic hypertension.

METHODS

We performed a large-scale multi-centre clinical genetic research of 1179 expertly selected hypertensive individuals from the Chinese Han population. Targeted sequencing were performed to evaluate 37 causative genes of potential cases of monogenic hypertension. Pathogenic and likely pathogenic variants were classified using the American College of Medical Genetics guidelines. Additionally, 49 variants of unknown significance (VUS) that had relatively high pathogenicity were selected and analysed using immunoblot protein expression assays.

RESULTS

21 pathogenic or likely pathogenic variants were identified in 33 of 1179 cases (2.80%). Gene product expression analyses showed 27 VUSs harboured by 49 individuals (4.16%) could lead to abnormally expressed protein levels. Consequently, combining genetic screening with gene product expression analyses increased the diagnostic yield from 2.80% to 6.79%. The main aetiologies established were primary aldosteronism (PA; 27, 2.29%) and pheochromocytoma and paraganglioma (PPGL; 10, 0.85%).

CONCLUSION

Molecular diagnoses obtained using causative gene screening combined with gene product expression analyses initially achieved a modest diagnostic yield. Our data highlight the predominant roles of PA and PPGL. Furthermore, we provide evidence indicating the enhanced diagnostic ability of combined genetic and functional evaluation.