[Genetics of paragangliomas and pheochromocytomas]

Genetic and epigenetic differences of benign and malignant pheochromocytomas and paragangliomas (PPGLs)

Pheochromocytomas and paragangliomas (PPGLs) are tumors arising from the adrenal medulla and sympathetic/parasympathetic paraganglia, respectively. According to Th e Cancer Genome Atlas (TCGA), approximately 40% of PPGLs are due to germ line mutations in one of 16 susceptibility genes, and a further 30% are due to somatic alterations in at least seven main genes (VHL, EPAS1, CSDE1, MAX, HRAS, NF1, RET, and possibly KIF1B). Th e diagnosis of malignant PPGL was straight forward in most cases as it was defined as presence of PPGL in non-chromaffin tissues. Accordingly, there is an extreme need for new diagnostic marker(s) to identify tumors with malignant prospective. Th e aim of this study was to review all suggested genetic and epigenetic alterations that are remarkably different between benign and malignant PPGLs. It seems that more than two genetic mutation clusters in PPGLs and other genetic and methylation biomarkers could be targeted for malignancy discrimination in different studies.

Treatment responses to antiangiogenetic therapy and chemotherapy in nonsecreting paraganglioma (PGL4) of urinary bladder with SDHB mutation: A case report

INTRODUCTION

Paraganglioma (PGL) is a rare neuroendocrine tumor. Currently, the malignancy is defined as the presence of metastatic spread at presentation or during follow-up. Several gene mutations are listed in the pathogenesis of PGL, among which succinate dehydrogenase (SDHX), particularly the SDHB isoform, is the main gene involved in malignancy. A 55-year-old male without evidence of catecholamine secretion had surgery for PGL of the urinary bladder. After 1 year, he showed a relapse of disease and demonstrated malignant PGL without evidence of catecholamine secretion with a germline heterozygous mutation of succinate dehydrogenase B (SDHB). After failure of a second surgery for relapse, he started medical treatment with sunitinib daily but discontinued due to serious side effects. Cyclophosphamide, vincristine, and dacarbazine (CVD) chemotherapeutic regimen stopped the disease progression for 7 months.

CONCLUSION

Malignant PGL is a very rare tumor, and SDHB mutations must be always considered in molecular diagnosis because they represent a critical event in the progression of the oncological disease. Currently, there are few therapeutic protocols, and it is often difficult, as this case demonstrates, to decide on a treatment option according to a reasoned set of choices.

Molecular markers of paragangliomas/pheochromocytomas

Paragangliomas/pheochromocytomas comprise rare tumors that arise from the extra-adrenal paraganglia, with an incidence of about 2 to 8 per million people each year. Approximately 40% of cases are due to genetic mutations in at least one out of more than 30 causative genes. About 25-30% of pheochromocytomas/paragangliomas develop under the conditions of a hereditary tumor syndrome a third of which are caused by mutations in the VHL gene. Together, the gene mutations in this disorder have implicated multiple processes including signaling pathways, translation initiation, hypoxia regulation, protein synthesis, differentiation, survival, proliferation, and cell growth. The present review contemplates the mutations associated with the development of pheochromocytomas/paragangliomas and their potential to serve as specific markers of these tumors and their progression. These data will improve our understanding of the pathogenesis of these tumors and likely reveal certain features that may be useful for early diagnostics, malignancy prognostics, and the determination of new targets for disease therapeutics.

Hypertension: The role of biochemistry in the diagnosis and management

Hypertension is defined as a persistently elevated blood pressure ≥140/90mmHg. It is an important treatable risk factor for cardiovascular disease, with a high prevalence in the general population. The most common cause, essential hypertension, is a widespread disease - however, secondary hypertension is under investigated and under diagnosed. Collectively, hypertension is referred to as a "silent killer" - frequently it displays no overt symptomatology. It is a leading risk factor for death and disability globally, with >40% of persons aged over 25 having hypertension. A vast spectrum of conditions result in hypertension spanning essential through resistant, to patients with an overt endocrine cause. A significant number of patients with hypertension have multiple cardiovascular risk factors at the time of presentation. Both routine and specialised biochemical investigations are paramount for the evaluation of these patients and their subsequent management. Biochemical testing serves to identify those hypertensive individuals who are at higher risk on the basis of evidence of dysglycaemia, dyslipidaemia, renal impairment, or target organ damage and to exclude identifiable causes of hypertension. The main target of biochemical testing is the identification of patients with a specific and treatable aetiology of hypertension. Information gleaned from biochemical investigation is used to risk stratify patients and tailor the type and intensity of subsequent management and treatment. We review the approach to the biochemical investigation of patients presenting with hypertension and propose a diagnostic algorithm for work-up.

Malignant paraganglioma in children treated with embolization prior to surgical excision

Background

Paragangliomas (PGL) are rare tumors derived from neural crest cells, whose origins may vary along the chain of the sympathetic nervous system. Such tumors are often characterized by secretion of catecholamines, but sometimes they are biochemically inactive, which makes diagnosis often challenging. Malignant paraganglioma is defined by the presence of this tumor at sites where chromaffin cells are usually not found or by local invasion of the primary tumor. Recurrence, either regional or metastatic, usually occurs within 5 years of the initial complete resection but long-term recurrence is also described. Malignancy is often linked to a SDHB mutation. Preoperative embolization has been applied in the surgical management of PGLs with the objective to decrease intra-operative blood loss and surgery length without complications.

Case Presentation

We report two cases of patients with abdominal or pelvic malignant PGLs who have been treated surgically at our center after preoperative embolization. Surgery was a very challenging procedure with multiple surgical teams involved and embolization did not prevent major blood loss and intraoperative complications. Patients required adjuvant treatment with either chemotherapy or radiotherapy.

Conclusions

Many studies in the adult population have established recommendations for the diagnosis and therapeutic management of PGL, but few studies concern the pediatric population. Because malignant PGL is more important in the pediatric population, screening and early diagnosis of PGL is advisable in children with genetic predisposing. Surgical resection is the mainstay of treatment, but a multimodal approach is often required due to the complexity of cases.  The role of preoperative embolization is not established and in our experience it has provided little benefit and major complications.

Universal genetic screening uncovers a novel presentation of an SDHAF2 mutation

CONTEXT

Hereditary pheochromocytoma/paraganglioma (PC/PGL) accounts for up to 60% of previously considered sporadic tumors. Guidelines suggest that phenotype should guide genetic testing. Next-generation sequencing technology can simultaneously sequence 9 of the 18 known susceptibility genes in a timely, cost-efficient manner.

OBJECTIVE

Our aim was to confirm that universal screening is superior to targeted testing in patients with histologically confirmed PC and PGL.

METHODS

In two tertiary referral hospitals in Ireland, NGS was carried out on all histologically confirmed cases of PC/PGL diagnosed between 2004 and 2013. The following susceptibility genes were sequenced: VHL, RET, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, and MAX. A multiplex ligation-dependent probe amplification analysis was performed in VHL, SDHB, SDHC, SDHD, and SDHAF2 genes to detect deletions and duplications.

RESULTS

A total of 31 patients were tested, 31% (n = 10) of whom were found to have a genetic mutation. Of those patients with a positive genotype, phenotype predicted genotype in only 50% (n = 5). Significant genetic mutations that would have been missed in our cohort by phenotypic evaluation alone include a mutation in TMEM127, two mutations in SDHAF2, and two mutations in RET. Target testing would have identified three of the latter mutations based on age criteria. However, 20% of patients (n = 2) would not have satisfied any criteria for targeted testing including one patient with a novel presentation of an SDHAF2 mutation.

CONCLUSION

This study supports the value of universal genetic screening for all patients with PC/PGL.

Malignant pheochromocytoma in a 16-year-old patient with neurofibromatosis type 1

Patients with neurofibromatosis type I (NF1) feature a high risk of developing benign and malignant tumors, mainly those with a neuroectodermal origin, the risk being about 4 times higher than in the general population. Pheochromocytoma (PHEO) is a sporadic tumor (1∶100,000) arising from the adrenal medulla. Pheochromocytoma is a rare condition when occurring in conjunction with NF1 and occurs in about 1% of patients, rarely in those of pediatric age. In this study we present a 16-year-old patient with NF1 and malignant PHEO. Loss of heterozygosity analysis in PHEOs shows a reduction to homozygosity, observed for both 17p and 17q markers. This case confirms the importance of surveillance for malignant neoplasias in NF1 patients during childhood and adolescence. On the other hand, since 30% of PHEOs had germline mutations and, more rarely, somatic mutations, patients with PHEO should be investigated for associated genetic syndromes.

Pheochromocytoma and paraganglioma syndromes: genetics and management update

Pheochromocytomas (pheos) and paragangliomas (pgls) are rare tumours of the autonomic nervous system, originating from paraganglia, which are dispersed neuroendocrine organs characterized by catecholamine and peptide-producing cells derived from the neural crest. Medical textbooks have traditionally suggested that 10% of pheos are heritable. However, the frequency of heritable pheo has been underestimated. Three syndromic conditions-Von Hippel-Lindau (vhl), multiple endocrine neoplasia type 2 (men2), and neurofibromatosis type 1 (nf1)-and three genes-subunits of the succinate dehydrogenase (SDH) complex: SDHB, SDHC, and SDHD-are established causes of hereditary pheo-pgl. In the last few years, four new genes (SDHA, SDHAF2, MAX, and TMEM127) have been found to be associated with predisposition to these tumours. The present review, illustrated by three case reports, gives an update of the genetic basis of pheo-pgl and of the parent-of-origin effect implicated in the transmission of SDHD and SDHAF2. We discuss the referral criteria that should guide the decision to offer genetic testing to affected patients. We also specify the genes that are most likely implicated-based on particular features such as malignancy, bilateralism, or childhood-onset-to help geneticists efficiently order appropriate genetic tests. Finally, we review the screening recommendations for carriers of a pheo-pgl predisposition mutation.

[Gastrointestinal stromal tumors (GIST): at the forefront of targeted therapies]

Although gastrointestinal stromal tumors (GIST) are the most frequent sarcomas, they were usually not diagnosed before 1998. GIST derive from interstitial cells of Cajal, and may develop along the digestive tract, mainly from stomach and small intestine. GIST are characterized by the expression of KIT (CD117), and mutations KIT or PDGFRA are present in 85 % of cases. More than 150 different types of mutations have been reported. They are responsible for a constitutive activation of these tyrosine kinase receptors, in absence of their specific ligand. Detection of these mutations may help to confirm the diagnosis or to evaluate the prognosis. The mutations also have a predictive value. Indeed patients with metastatic GIST and duplication within exon 9 of KIT deserve to receive twice the dose of imatinib, while GIST with PDGFRA p.D842 V mutation are resistant to this drug. This review presents the main characteristics of GIST, and focus on the important insights of studies on GIST and their cell models in the field of oncology.