Systematic screening and treatment evaluation of hereditary neck paragangliomas

Clinical Practice Guidance: Surveillance for phaeochromocytoma and paraganglioma in paediatric succinate dehydrogenase gene mutation carriers

The succinate dehydrogenase (SDH) enzyme complex functions as a key enzyme coupling the oxidation of succinate to fumarate in the citric acid cycle. Inactivation of this enzyme complex results in the cellular accumulation of the oncometabolite succinate, which is postulated to be a key driver in tumorigenesis. Succinate accumulation inhibits 2-oxoglutarate-dependent dioxygenases, including DNA and histone demethylase enzymes and hypoxic gene response regulators. Biallelic inactivation (typically resulting from one inherited and one somatic event) at one of the four genes encoding the SDH complex (SDHA/B/C/D) is the most common cause for SDH deficient (dSDH) tumours. Germline mutations in the SDHx genes predispose to a spectrum of tumours including phaeochromocytoma and paraganglioma (PPGL), wild type gastrointestinal stromal tumours (wtGIST) and, less commonly, renal cell carcinoma and pituitary tumours. Furthermore, mutations in the SDHx genes, particularly SDHB, predispose to a higher risk of malignant PPGL, which is associated with a 5-year mortality of 50%. There is general agreement that biochemical and imaging surveillance should be offered to asymptomatic carriers of SDHx gene mutations in the expectation that this will reduce the morbidity and mortality associated with dSDH tumours. However, there is no consensus on when and how surveillance should be performed in children and young adults. Here, we address the question: "What age should clinical, biochemical and radiological surveillance for PPGL be initiated in paediatric SDHx mutation carriers?".

Can subunit-specific phenotypes guide surveillance imaging decisions in asymptomatic SDH mutation carriers?

OBJECTIVE

With the discovery that familial phaeochromocytoma and paraganglioma syndrome can be caused by mutations in each subunit of the succinate dehydrogenase enzyme (SDH), has come the recognition that mutations in the individual subunits have their own distinct natural histories. Increased genetic screening is leading to the identification of increasing numbers of, mostly asymptomatic, gene mutation carriers and the implementation of screening strategies for these individuals. Yet there is, to date, no international consensus regarding screening strategies for asymptomatic carriers.

DESIGN

A comprehensive PubMed search from 1/1/2000 to 28/2/2018 was undertaken using multiple search terms and subsequently a manual review of references in identified papers to identify all clinically relevant cases and cohorts. In this review, the accumulated, published experience of phenotype and malignancy risks of individual SDH subunits is analysed. Where possible screening results for asymptomatic SDH mutation carriers have been analysed separately to define the penetrance in asymptomatic carriers (asymptomatic penetrance).

RESULTS

The combined data confirms that "asymptomatic penetrance" is highest for SDHD and when there is penetrance, the most likely site to develop a PGL is head and neck (SDHD) and extra-adrenal abdominal (SDHB). However, the risk in SDHB carriers of developing HNPGL is also high (35.5%) and a PCC is low (15.1%), and in SDHD carriers there is a high risk of developing a PCC (35.8%) or abdominal PGL (9.4%) and a small, but significant risk at other sympathetic sites. The data suggest that the risk of malignant transformation is the same for both PCC and extra-adrenal abdominal PGLs (30%-35%) in SDHB carriers. In SDHD carriers, the risk of malignant transformation was highest in HNPGLs (7.5%) and similar for sympathetic sites (3.8%-5.2%).

CONCLUSIONS

Using this data, we suggest surveillance screening of asymptomatic carriers can be tailored to the underlying SDH subunit and review possible surveillance programmes.

The spectrum of SDHD mutations in Russian patients with head and neck paraganglioma

AIM OF THE STUDY

It was found that the mutations in the SDHD gene, encoding one of subunits of the succinate dehydrogenase complex, lead to the development of head and neck paraganglioma (HNPGL). We analyzed this gene in 91 patients with HNPGL from Russia.

MATERIALS AND METHODS

DNA was isolated from the whole blood. A screening for mutations was performed by Sanger sequencing.

RESULTS

We revealed three missense mutations that have been described previously: p.Pro81Leu, p.His102Arg, p.Tyr114Cys. Moreover, we identified a novel potentially pathogenic variant (p.Trp105*).

CONCLUSIONS

We found that mutations in the SDHD gene were less common in Russian patients compared with the majority of European populations. It was shown that the p.His102Arg mutation is a major mutation in Russia. We confirmed the previous suggestion that a bilateral localization of the tumor and the carotid type represent a marker of the genetically determined form of HNPGL.

Active surveillance management of head and neck paragangliomas: case series and review of the literature

Background:

Head and neck paragangliomas are rare. They are usually slow-growing, benign, non-catecholamine secreting tumours, traditionally treated with surgical excision. Complications of surgical excision include lower cranial nerve palsies, stroke and death.

Method:

A retrospective case note analysis was conducted of patients with head and neck paragangliomas treated with a watch-and-scan policy from March 2003 to September 2015, and the relevant literature was reviewed.

Results:

Fifteen head and neck paragangliomas were identified. None of the patients developed a new lower cranial nerve palsy or progression of their presenting hearing loss during the follow-up period. Five patients displayed an increase in maximum linear dimension of 4 mm over an average of 57.4 months. A review of the literature showed that a watch-and-surveillance scan policy is evolving as a treatment option for head and neck paragangliomas without malignant risk factors.

Conclusion:

Readily available surveillance scanning in head and neck paragangliomas enables the monitoring of head and neck paragangliomas, which may allow for avoidance of major surgery.

Identification of eight novel SDHB, SDHC, SDHD germline variants in Danish pheochromocytoma/paraganglioma patients

Background

Germline mutations in the succinate dehydrogenase complex genes SDHB, SDHC, and SDHD predispose to pheochromocytomas and paragangliomas. Here, we examine the SDHB, SDHC, and SDHD mutation spectrum in the Danish population by screening of 143 Danish pheochromocytoma and paraganglioma patients.

Methods

Mutational screening was performed by Sanger sequencing or next-generation sequencing. The frequencies of variants of unknown clinical significance, e.g. intronic, missense, and synonymous variants, were determined using the Exome Aggregation Consortium database, while the significance of missense mutations was predicted by in silico and loss of heterozygosity analysis when possible.

Results

We report 18 germline variants; nine in SDHB, six in SDHC, and three in SDHD. Of these 18 variants, eight are novel. We classify 12 variants as likely pathogenic/pathogenic, one as likely benign, and five as variants of unknown clinical significance.

Conclusions

Identifying and classifying SDHB, SDHC, and SDHD variants present in the Danish population will augment the growing knowledge on variants in these genes and may support future clinical risk assessments.

Treatment of cervical paragangliomas

OBJECTIVE

Review of the treatment of cervical paraganglioma.

MATERIAL AND METHODS

Review of the literature based on a Medline database.

RESULTS

The treatment of choice consists of a multidisciplinary approach based on a detailed clinical, laboratory and radiological work-up. Vascular reconstruction may be necessary when the tumour invades the artery wall. The main complication of surgery is damage to cranial nerves involved in speech and/or swallowing. Treatment of bilateral tumours must be conducted in two stages. The first side to be operated depends on the sites and size of the tumours, as the primary objective is to avoid bilateral vagus nerve palsy. Radiotherapy has been used to treat paragangliomas for several years and achieves tumour stabilization in the majority of cases. Potential indications reported in the literature are: inoperable tumours, recurrence after surgery, some bilateral tumours and malignant tumours.

CONCLUSION

Surgery is the standard treatment for cervical paraganglioma. Radiotherapy can be proposed when surgery is contraindicated.

Structural basis for malfunction in complex II

Complex II couples oxidoreduction of succinate and fumarate at one active site with that of quinol/quinone at a second distinct active site over 40 Å away. This process links the Krebs cycle to oxidative phosphorylation and ATP synthesis. The pathogenic mutation or inhibition of human complex II or its assembly factors is often associated with neurodegeneration or tumor formation in tissues derived from the neural crest. This brief overview of complex II correlates the clinical presentations of a large number of symptom-associated alterations in human complex II activity and assembly with the biochemical manifestations of similar alterations in the complex II homologs from Escherichia coli. These analyses provide clues to the molecular basis for diseases associated with aberrant complex II function.

The endemic paraganglioma syndrome type 1: origin, spread, and clinical expression

CONTEXT

Anecdotal evidence suggests a high incidence in Trentino, Italy, of head and neck paragangliomas (HNPGL), a rare autosomal dominant disease called paraganglioma type 1 syndrome and caused by germ-line mutations of the SDHD gene.

OBJECTIVE

The aim of this study was to investigate the origin, spread, and clinical expression of the disease in this geographic region.

DESIGN, SETTING, AND PARTICIPANTS

Trentino natives with HNPGL were recruited for establishing clinical expression of the disease, presence of a founder effect, and age of common ancestor. A large sample of the local population was recruited for determination of mutation prevalence and spread.

MAIN OUTCOME MEASURES

SDHD genetic testing was offered to first-degree relatives, and clinical surveillance was offered to at-risk carriers. The hypothesis of a founder effect was explored by haplotype analysis, and time to the most recent common ancestor was estimated by decay of haplotype sharing over time.

RESULTS

A total of 287 of the 540 recruited individuals from 95 kindreds carried the SDHD c.341A>G p.Tyr114Cys mutation. The prevalent phenotype was bilateral or multiple HNPGL, with low prevalence of pheochromocytoma and malignant forms. Penetrance was high. A common ancestor was dated between the 14th and 15th century, with the mutation spreading from the Mocheni Valley, a geographic, cultural and, presumably, a genetic isolate to 1.5% of the region's population.

CONCLUSIONS

A combination of particular demographic, geographical, and historical conditions has resulted in the oldest and largest SDHD founder effect so far characterized and has transformed a rare disease into an endemic disease with major public health implications.

SDH mutations in tumorigenesis and inherited endocrine tumours: lesson from the phaeochromocytoma-paraganglioma syndromes

A genetic predisposition for paragangliomas and adrenal or extra-adrenal phaeochromocytomas was recognized years ago. Beside the well-known syndromes associated with an increased risk of adrenal phaeochromocytoma, Von Hippel Lindau disease, multiple endocrine neoplasia type 2 and neurofibromatosis type 1, the study of inherited predisposition to head and neck paragangliomas led to the discovery of the novel 'paraganglioma-phaeochromocytoma syndrome' caused by germline mutations in three genes encoding subunits of the succinate dehydrogenase (SDH) enzyme (SDHB, SDHC and SDHD) thus opening an unexpected connection between mitochondrial tumour suppressor genes and neural crest-derived cancers. Germline mutations in SDH genes are responsible for 6% and 9% of sporadic paragangliomas and phaeochromocytomas, respectively, 29% of paediatric cases, 38% of malignant tumours and more than 80% of familial aggregations of paraganglioma and phaeochromocytoma. The disease is characterized by autosomal dominant inheritance with a peculiar parent-of-origin effect for SDHD mutations. Life-time tumour risk seems higher than 70% with variable clinical manifestantions depending on the mutated gene. In this review we summarize the most recent knowledge about the role of SDH deficiency in tumorigenesis, the spectrum and prevalence of SDH mutations derived from several series of cases, the related clinical manifestantions including rare phenotypes, such as the association of paragangliomas with gastrointestinal stromal tumours and kidney cancers, and the biological hypotheses attempting to explain genotype to phenotype correlation.

The first Dutch SDHB founder deletion in paraganglioma-pheochromocytoma patients

Background

Germline mutations of the tumor suppressor genes SDHB, SDHC and SDHD play a major role in hereditary paraganglioma and pheochromocytoma. These three genes encode subunits of succinate dehydrogenase (SDH), the mitochondrial tricarboxylic acid cycle enzyme and complex II component of the electron transport chain. The majority of variants of the SDH genes are missense and nonsense mutations. To date few large deletions of the SDH genes have been described.

Methods

We carried out gene deletion scanning using MLPA in 126 patients negative for point mutations in the SDH genes. We then proceeded to the molecular characterization of deletions, mapping breakpoints in each patient and used haplotype analysis to determine whether the deletions are due to a mutation hotspot or if a common haplotype indicated a single founder mutation.

Results

A novel deletion of exon 3 of the SDHB gene was identified in nine apparently unrelated Dutch patients. An identical 7905 bp deletion, c.201-4429_287-933del, was found in all patients, resulting in a frameshift and a predicted truncated protein, p.Cys68HisfsX21. Haplotype analysis demonstrated a common haplotype at the SDHB locus. Index patients presented with pheochromocytoma, extra-adrenal PGL and HN-PGL. A lack of family history was seen in seven of the nine cases.

Conclusion

The identical exon 3 deletions and common haplotype in nine patients indicates that this mutation is the first Dutch SDHB founder mutation. The predominantly non-familial presentation of these patients strongly suggests reduced penetrance. In this small series HN-PGL occurs as frequently as pheochromocytoma and extra-adrenal PGL.

Surgical management of carotid body tumors

BACKGROUND

Carotid body tumors (CBT) should be considered when evaluating every lateral neck mass.

METHODS

A retrospective study was conducted of 52 patients with 57 CBT. The surgical approach and complications were reviewed. All patients were operated on without preoperative embolization.

RESULTS

Multifocal paraganglioma (PG) were detected in six cases. A succinate dehydrogenase subunit D (SDHD) mutation was discovered in four patients. Vascular peroperative complication occurred in one case. Vascular reconstruction was decided peroperatively in five cases (8.8%). Vascular reconstruction was 0% for Shamblin 1 or 2 tumors, but 28.5% for Shamblin 3. A postoperative nerve paresis was reported in 24 patients (42.1%) and vagal nerve paralysis persisted in four cases (7.01%). The rate of serious complications, e.g., permanent nerve palsy, preoperative and postoperative complications, was 14.03%; it was 2.3% for Shamblin 1 or 2 tumors and 35.7% for Shamblin 3. One patient had malignant PG with node metastasis and was not referred for radiotherapy. No recurrence or metastasis was reported after 6-year follow-up.

CONCLUSION

Early surgical treatment is recommended in almost all patients after preoperative evaluation and detection of multifocal tumors. Surgical excision of small tumors was safe and without complication, but resection of Shamblin 3 tumors can be challenging. Routine preoperative embolization of carotid body paragangliomas is not required.