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Phaeochromocytomas and paragangliomas (collectively termed PPGL) are rare yet highly heritable neuroendocrine tumours, with over one-third of cases associated with germline pathogenic variants (PVs) in numerous genes. PVs in the succinate dehydrogenase subunit-A gene (SDHA) were initially implicated in hereditary PPGL in 2010, and SDHA has since become an important susceptibility gene accounting for up to 2.8% of cases. However, it remains poorly understood, particularly regarding the clinical nature of SDHA PPGL, rates of recurrence and metastasis, and the nature of metastatic disease. We present a narrative review of SDHA-related PPGL, covering pathophysiology, relevance to current clinical practice, and considerations for clinical genetics. We analyse a pool of 107 previously reported cases of SDHA-associated PPGL to highlight the spectrum of SDHA-related PPGL. Our analysis demonstrates that SDHA PPGL occurs across a wide age range (11-81 years) and affects men and women equally. SDHA PPGL typically presents as single tumours (91%), usually occurring in the head and neck (46%) or abdomen (43%, including 15% with phaeochromocytomas). Metastatic disease was reported in 25.5% of cases, with bone (82%) and lymph nodes (71%) being the most common sites of metastasis, often identified many years after the initial diagnosis. A family history of SDHA-related neoplasia was rare, reported in only 4% of cases. Understanding the clinical nature and risks associated with SDHA PVs is essential for facilitating the optimal management of patients and their families.

Context: Carriers of germline pathogenic variants (PVs) in succinate dehydrogenase type B (SDHB) are at increased risk of developing pheochromocytomas and paragangliomas (PPGLs). Understanding their outcomes can guide recommendations for risk assessment and early detection., Objective: We performed a systematic review and meta-analysis of the following outcomes in SDHB PV carriers: age-specific risk of developing tumors, metastatic progression, second primary tumor development, and mortality., Methods: PubMed, MEDLINE, and EMBASE were searched. Sixteen studies met the inclusion criteria and were sorted into 4 outcome categories: age-specific penetrance, metastatic disease, risk of second tumor, and mortality. We assessed heterogeneity and performed a meta-analysis across studies using a random-effects model with the DerSimonian and Laird method., Results: Penetrance of PPGLs for nonproband/nonindex SDHB PV carriers by age 20 was 4% (95% CI, 3%-6%), 11% (95% CI, 8%-15%) by age 40, 24% (95% CI, 19%-31%) by age 60%, and 35% (95% CI, 25%-47%) by age 80. The overall risk of metastatic disease for nonproband/nonindex carriers with PPGLs was 9% (95%, CI 5%-16%) per lifetime. In all affected cases (combining both proband/index and nonproband/nonindex carriers with tumors), the risk of a second tumor was 24% (95% CI, 18%-31%) and all-cause 5-year mortality was 18% (95% CI, 6%-40%)., Conclusion: Penetrance for PPGLs in SDHB PV carriers increases linearly with age. Affected carriers are at risk of developing and dying of metastatic disease, or of developing second tumors. Lifelong surveillance is appropriate., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society.)

Phaeochromocytoma and paraganglioma are highly heritable tumours; half of those associated with a germline mutation are caused by mutations in genes for Krebs's cycle enzymes, including succinate dehydrogenase (SDH). Inheritance of SDH alleles is assumed to be Mendelian (probability of 50% from each parent). The departure from transmission of parental alleles in a ratio of 1:1 is termed transmission ratio distortion (TRD). We sought to assess whether TRD occurs in the transmission of SDHB pathogenic variants (PVs). This study was conducted with 41 families of a discovery cohort from Royal North Shore Hospital, Australia, and 41 families from a validation cohort from St. Bartholomew's Hospital, United Kingdom (UK). Inclusion criteria were a clinically diagnosed SDHB PV and a pedigree available for at least two generations. TRD was assessed in 575 participants with the exact binomial test. The transmission ratio for SDHB PV was 0.59 (P = 0.005) in the discovery cohort, 0.67 (P < 0.001) in the validation cohort, and 0.63 (P < 0.001) in the combined cohort. No parent-of-origin effect was observed. TRD remained significant after adjusting for potential confounders: 0.67 (P < 0.001) excluding families with incomplete family size data; 0.58 (P < 0.001) when probands were excluded. TRD was also evident for SDHD PVs in a cohort of 81 patients from 13 families from the UK. The reason for TRD of SDHB and SDHD PVs is unknown, but we hypothesize a survival advantage selected during early embryogenesis. The existence of TRD for SDHB and SDHD has implications for reproductive counselling, and further research into the heterozygote state.

Up to 40% of pheochromocytomas (PCCs) and paragangliomas (PGLs) are hereditary. Germline mutations/deletions in fumarate hydratase ( FH ) cause hereditary leiomyomatosis and renal cell carcinoma syndrome which manifests predominantly with FH-deficient uterine/cutaneous leiomyomas and renal cell carcinomas (RCCs)-tumors characterized by loss of immunohistochemical (IHC) expression of FH and/or positive staining for S-(2-succino)-cysteine. Occasional patients develop PCC/PGL. We investigated the incidence, morphologic, and clinical features of FH-deficient PCC/PGL. We identified 589 patients with PCC/PGLs that underwent IHC screening for FH and/or S-(2-succino)-cysteine. Eight (1.4%) PCC/PGLs were FH deficient (1.1% in an unselected population). The median age for FH-deficient cases was 55 (range: 30 to 77 y) with 50% arising in the adrenal. All 4 with biochemical data were noradrenergic. Two (25%) metastasized, 1 dying of disease after 174 months. Germline testing was performed on 7 patients, 6 of whom had FH missense mutations. None were known to have a significant family history before presentation or developed cutaneous leiomyomas, or FH-deficient RCC at extended follow-up. The patient wild-type for FH on germline testing was demonstrated to have somatic FH mutation and loss of heterozygosity corresponding to areas of subclonal FH deficiency in her tumor. One patient did not undergo germline testing, but FH mutation was demonstrated in his tumor. We conclude that FH-deficient PCC/PGL are underrecognized but can be identified by IHC. FH-deficient PCC/PGL are strongly associated with germline missense mutations but are infrequently associated with leiomyoma or RCC, suggesting there may be a genotype-phenotype correlation. FH-deficient PCC/PGL may have a higher metastatic risk., Competing Interests: Conflicts of Interest and Source of Funding: R.J.C.B. has served on advisory boards for Amgen, Eisai, Kyowa Kirin, Ipsen and received speaking honoraria from Amgen, Eisai, and Kyowa Kirin unrelated to the current work. For the remaining authors none were declared., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc.)

Context: Carriers of succinate dehydrogenase type B (SDHB) pathogenic variants (PVs) are at risk of pheochromocytoma and paraganglioma (PPGL) from a young age. It is widely recommended carriers enter a surveillance program to detect tumors, but there are limited studies addressing outcomes of surveillance protocols for SDHB PV carriers., Objective: The purpose of this study was to describe surveillance-detected (s-d) tumors in SDHB PV carriers enrolled in a surveillance program and to compare their outcomes to probands., Methods: This was a multicenter study of SDHB PV carriers with at least 1 surveillance episode (clinical, biochemical, imaging) in Australian genetics clinics. Data were collected by both retrospective and ongoing prospective follow-up. Median duration of follow-up was 6.0 years., Results: 181 SDHB PV carriers (33 probands and 148 nonprobands) were assessed. Tumors were detected in 20% of nonprobands undergoing surveillance (age range 9-76 years). Estimated 10-year metastasis-free survival was 66% for probands and 84% for nonprobands with s-d tumors (P = .027). S-d tumors were smaller than those in probands (median 27 mm vs 45 mm respectively, P = .001). Tumor size ≥40 mm was associated with progression to metastatic disease (OR 16.9, 95% CI 2.3-187.9, P = .001). Patients with s-d tumors had lower mortality compared to probands: 10-year overall survival was 79% for probands and 100% for nonprobands (P = .029)., Conclusion: SDHB carriers with s-d tumors had smaller tumors, reduced risk of metastatic disease, and lower mortality than probands. Our results suggest that SDHB PV carriers should undertake surveillance to improve clinical outcomes., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society.)

Mosaic or somatic EPAS1 mutations are associated with a range of phenotypes including pheochromocytoma and/or paraganglioma (PPGL), polycythemia and somatostatinoma. The pathogenic potential of germline EPAS1 variants however is not well understood. We report a number of germline EPAS1 variants occurring in patients with PPGL, including a novel variant c.739C>A (p.Arg247Ser); a previously described variant c.1121T>A (p.Phe374Tyr); several rare variants, c.581A>G (p.His194Arg), c.2353C>A (p.Pro785Thr) and c.2365A>G (p.Ile789Val); a common variant c.2296A>C (p.Thr766Pro). We performed detailed functional studies to understand their pathogenic role in PPGL. In transient transfection studies, EPAS1/HIF-2α p.Arg247Ser, p.Phe374Tyr and p.Pro785Thr were all stable in normoxia. In co-immunoprecipitation assays, only the novel variant p.Arg247Ser showed diminished interaction with pVHL. A direct interaction between HIF-2α Arg247 and pVHL was confirmed in structural models. Transactivation was assessed by means of a HRE-containing reporter gene in transiently transfected cells, and significantly higher reporter activity was only observed with EPAS1/HIF-2α p.Phe374Tyr and p.Pro785Thr. In conclusion, three germline EPAS1 variants (c.739C>A (p.Arg247Ser), c.1121T>A (p.Phe374Tyr) and c.2353C>A (p.Pro785Thr)) all have some functional features in common with somatic activating mutations. Our findings suggest that these three germline variants are hypermorphic alleles that may act as modifiers to the expression of PPGLs.

Background: Until recently, determining penetrance required large observational cohort studies. Data from the Exome Aggregate Consortium (ExAC) allows a Bayesian approach to calculate penetrance, in that population frequencies of pathogenic germline variants should be inversely proportional to their penetrance for disease. We tested this hypothesis using data from two cohorts for succinate dehydrogenase subunits A, B and C ( SDHA-C ) genetic variants associated with hereditary pheochromocytoma/paraganglioma (PC/PGL)., Methods: Two cohorts were 575 unrelated Australian subjects and 1240 unrelated UK subjects, respectively, with PC/PGL in whom genetic testing had been performed. Penetrance of pathogenic SDHA-C variants was calculated by comparing allelic frequencies in cases versus controls from ExAC (removing those variants contributed by The Cancer Genome Atlas)., Results: Pathogenic SDHA-C variants were identified in 106 subjects (18.4%) in cohort 1 and 317 subjects (25.6%) in cohort 2. Of 94 different pathogenic variants from both cohorts (seven in SDHA , 75 in SDHB and 12 in SDHC ), 13 are reported in ExAC (two in SDHA , nine in SDHB and two in SDHC ) accounting for 21% of subjects with SDHA-C variants. Combining data from both cohorts, estimated lifetime disease penetrance was 22.0% (95% CI 15.2% to 30.9%) for SDHB variants, 8.3% (95% CI 3.5% to 18.5%) for SDHC variants and 1.7% (95% CI 0.8% to 3.8%) for SDHA variants., Conclusion: Pathogenic variants in SDHB are more penetrant than those in SDHC and SDHA . Our findings have important implications for counselling and surveillance of subjects carrying these pathogenic variants., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2018. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Pheochromocytomas (PC) and paragangliomas (PGL) are endocrine tumors for which the genetic and clinicopathological features of metastatic progression remain incompletely understood. As a result, the risk of metastasis from a primary tumor cannot be predicted. Early diagnosis of individuals at high risk of developing metastases is clinically important and the identification of new biomarkers that are predictive of metastatic potential is of high value. Activation of TERT has been associated with a number of malignant tumors, including PC/PGL. However, the mechanism of TERT activation in the majority of PC/PGL remains unclear. As TERT promoter mutations occur rarely in PC/PGL, we hypothesized that other mechanisms - such as structural variations - may underlie TERT activation in these tumors. From 35 PC and four PGL, we identified three primary PCs that developed metastases with elevated TERT expression, each of which lacked TERT promoter mutations and promoter DNA methylation. Using whole genome sequencing, we identified somatic structural alterations proximal to the TERT locus in two of these tumors. In both tumors, the genomic rearrangements led to the positioning of super-enhancers proximal to the TERT promoter, that are likely responsible for the activation of the normally tightly repressed TERT expression in chromaffin cells., (© 2018 Society for Endocrinology.)

Background: Germline mutations in genes encoding subunits of succinate dehydrogenase (SDH) are associated with the development of pheochromocytoma (PC) and/or paraganglioma (PGL). As assembly factors have been identified as playing a role in maturation of individual SDH subunits and assembly of the functioning SDH complex, we hypothesized that SDHAF3 variants may be associated with PC/PGL and functionality of SDH., Methods: DNA was extracted from the blood of 37 individuals (from 23 families) with germline SDH mutations and 18 PC/PGL (15 sporadic, 3 familial) and screened for mutations using a custom gene panel, containing SDHAF3 (SDH assembly factor 3) as well as eight known PC/PGL susceptibility genes. Molecular and functional consequences of an identified sequence variant of SDHAF3 were assessed in yeast and mammalian cells (HEK293)., Results: Using massively parallel sequencing, we identified a variant in SDHAF3, c.157 T > C (p.Phe53Leu), associated with increased prevalence in familial and sporadic PC/PGL (6.6%) when compared to normal populations (1.2% [1000 Genomes], p = 0.003; 2.1% [Exome Aggregation Consortium], p = 0.0063). In silico prediction tools suggest this variant is probably damaging to protein function, hence we assessed molecular and functional consequences of the resulting amino acid change (p.Phe53Leu) in yeast and human cells. We showed that introduction of SDHAF3 p.Phe53Leu into Sdh7 (ortholog of SDHAF3 in humans) null yeast resulted in impaired function, as observed by its failure to restore SDH activity when expressed in Sdh7 null yeast relative to WT SDHAF3. As SDHAF3 is involved in maturation of SDHB, we tested the functional impact of SDHAF3 c.157 T > C and various clinically relevant SDHB mutations on this interaction. Our in vitro studies in human cells show that SDHAF3 interacts with SDHB (residues 46 and 242), with impaired interaction observed in the presence of the SDHAF3 c.157 T > C variant., Conclusions: Our studies reveal novel insights into the biogenesis of SDH, uncovering a vital interaction between SDHAF3 and SDHB. We have shown that SDHAF3 interacts directly with SDHB (residue 242 being key to this interaction), and that a variant in SDHAF3 (c.157 T > C [p.Phe53Leu]) may be more prevalent in individuals with PC/PGL, and is hypomorphic via impaired interaction with SDHB.

Phaeochromocytomas and paragangliomas (PPGLs) are neural-crest-derived tumours of the sympathetic or parasympathetic nervous system that are often inherited and are genetically heterogeneous. Genetic testing is recommended for patients with these tumours and for family members of patients with hereditary forms of PPGLs. Due to the large number of susceptibility genes implicated in the diagnosis of inherited PPGLs, next-generation sequencing (NGS) technology is ideally suited for carrying out genetic screening of these individuals. This Consensus Statement, formulated by a study group comprised of experts in the field, proposes specific recommendations for the use of diagnostic NGS in hereditary PPGLs. In brief, the study group recommends target gene panels for screening of germ line DNA, technical adaptations to address different modes of disease transmission, orthogonal validation of NGS findings, standardized classification of variant pathogenicity and uniform reporting of the findings. The use of supplementary assays, to aid in the interpretation of the results, and sequencing of tumour DNA, for identification of somatic mutations, is encouraged. In addition, the study group launches an initiative to develop a gene-centric curated database of PPGL variants, with annual re-evaluation of variants of unknown significance by an expert group for purposes of reclassification and clinical guidance.

Objective: Mutations of genes encoding the four subunits of succinate dehydrogenase (SDH) have been associated with pheochromocytoma and paraganglioma (PPGLs), gastrointestinal stromal tumors (GISTs) and renal cell carcinomas (RCCs). These tumors have not been characterized in a way that reflects severity of SDH dysfunction. Mass spectrometric analysis now allows measurement of metabolites extracted from formalin fixed paraffin embedded (FFPE) specimens. We assess whether SDH deficiency in various tumor types characterized by loss of SDHB protein expression correlates with SDH dysfunction as assessed by the ratio of succinate:fumarate in FFPE specimens., Patients and Methods: Sections of FFPE tumor specimens from 18 PPGL, 10 GIST and 11 RCC patients with known SDHx mutation status for SDH deficiency were collected for mass spectrometric analysis of succinate and fumarate., Results: FFPE samples showed higher succinate:fumarate ratios in SDH-deficient PPGLs compared to SDH-sufficient PPGLs. Similarly, a higher succinate:fumarate ratio was able to distinguish SDH-deficient GISTs and RCCs from their SDH-sufficient counterparts with great selectivity. Interestingly, the cut-off value of the succinate:fumarate ratio was two-folds greater in RCCs than GISTs., Conclusion: Analyzing biochemical imbalances preserved in FFPE specimens with mass spectrometry expands the method and sample type repertoire available for characterisation of multiple neoplasias associated with SDH deficiency.

The paraganglioma (PGL) syndromes types 1-5 are autosomal dominant disorders characterized by familial predisposition to PGLs, phaeochromocytomas (PCs), renal cell cancers, gastrointestinal stromal tumours and, rarely, pituitary adenomas. Each syndrome is associated with mutation in a gene encoding a particular subunit (or assembly factor) of succinate dehydrogenase (SDHx). The clinical manifestations of these syndromes are protean: patients may present with features of catecholamine excess (including the classic triad of headache, sweating and palpitations), or with symptoms from local tumour mass, or increasingly as an incidental finding on imaging performed for some other purpose. As genetic testing for these syndromes becomes more widespread, presymptomatic diagnosis is also possible, although penetrance of disease in these syndromes is highly variable and tumour development does not clearly follow a predetermined pattern. PGL1 syndrome (SDHD) and PGL2 syndrome (SDHAF2) are notable for high frequency of multifocal tumour development and for parent-of-origin inheritance: disease is almost only ever manifest in subjects inheriting the defective allele from their father. PGL4 syndrome (SDHB) is notable for an increased risk of malignant PGL or PC. PGL3 syndrome (SDHC) and PGL5 syndrome (SDHA) are less common and appear to be associated with lower penetrance of tumour development. Although these syndromes are all associated with SDH deficiency, few genotype-phenotype relationships have yet been established, and indeed it is remarkable that such divergent phenotypes can arise from disruption of a common molecular pathway. This article reviews the clinical presentations of these syndromes, including their component tumours and underlying genetic basis., (© 2015 The authors.)

Mitochondrial dysfunction, due to mutations of the gene encoding succinate dehydrogenase (SDH), has been implicated in the development of adrenal phaeochromocytomas, sympathetic and parasympathetic paragangliomas, renal cell carcinomas, gastrointestinal stromal tumours and more recently pituitary tumours. Underlying mechanisms behind germline SDH subunit B (SDHB) mutations and their associated risk of disease are not clear. To investigate genotype-phenotype correlation of SDH subunit B (SDHB) variants, a homology model for human SDH was developed from a crystallographic structure. SDHB mutations were mapped, and biochemical effects of these mutations were predicted in silico. Results of structural modelling indicated that many mutations within SDHB are predicted to cause either failure of functional SDHB expression (p.Arg27*, p.Arg90*, c.88delC and c.311delAinsGG), or disruption of the electron path (p.Cys101Tyr, p.Pro197Arg and p.Arg242His). GFP-tagged WT SDHB and mutant SDHB constructs were transfected (HEK293) to determine biological outcomes of these mutants in vitro. According to in silico predictions, specific SDHB mutations resulted in impaired mitochondrial localisation and/or SDH enzymatic activity. These results indicated strong genotype-functional correlation for SDHB variants. This study reveals new insights into the effects of SDHB mutations and the power of structural modelling in predicting biological consequences. We predict that our functional assessment of SDHB mutations will serve to better define specific consequences for SDH activity as well as to provide a much needed assay to distinguish pathogenic mutations from benign variants., (© 2015 Society for Endocrinology.)

Background: Broad or general consent given by cancer patients for their tissue, blood, and clinical information to be stored in institutional biorepositories is fundamental to enable future ethical translational cancer research. The decision to consent for biobanking will contribute to the development of advanced diagnostic and prognostic tests, as well as new therapies to improve patient outcomes. While the rate of patient participation in biobanking programs is generally reported as high worldwide, few studies have investigated factors that may influence this decision. Biobanking at our medical research institute, an associated public (government-run) university hospital, and private hospital has been established for over 20 years, with collection of certain tumor types embedded in the research culture of these institutions. In this study, we investigated factors that may influence a cancer patient's decision to give broad consent for biobanking of their specimens., Methods: Data on patient consent were collected over a 6-month period from both government and private hospitals associated with our medical research institute. Factors considered included gender, patient age at surgery, type of malignancy (breast, duodenal, cervical, endometrial, gastric, liver, esophageal, ovarian, pancreatic, pelvic, uterine, or vulval), type of institution where surgery was performed, and timing of consent., Results: Of 171 cancer patients, 159 (93%) gave broad consent for biobanking of their tissue and blood specimens for future cancer research projects receiving ethical and scientific approval. None of the factors analyzed was shown to influence a patient's decision to contribute biological specimens and clinical data to a biorepository for future medical research., Conclusion: Biobanking for future ethically and scientifically approved research projects in an established institution is an initiative that receives strong support from patients undergoing cancer surgery, independent of factors including gender, age, type of tumor, type of institution where surgery was performed, or timing of consent.

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

Phaeochromocytomas (PCs) are tumours of the adrenal medulla chromaffin cells. Paragangliomas (PGLs) arise in sympathetic ganglia (previously called extra-adrenal PCs) or in non-chromaffin parasympathetic ganglia cells that are usually non-secretory. Parenchymal cells from these tumours have a common embryological origin from neural crest ectoderm. Several case series of canine PCs and PGLs have been published and a link between the increased incidence of chemoreceptor neoplasia in brachycephalic dog breeds and chronic hypoxia has been postulated. A similar link to hypoxia in man led to the identification of germline heterozygous mutations in the gene encoding succinate dehydrogenase subunit D (SDHD) and subsequently SDHA, SDHB and SDHC in similar tumours. We investigated canine PCs (n = 6) and PGLs (n = 2) for SDHD and SDHB mutations and in one PGL found a somatic SDHD mutation c.365A>G (p.Lys122Arg) in exon 4, which was not present in normal tissue from this brachycephalic dog. Two PCs were heterozygous for both c.365A>G (p.Lys122Arg) mutation and an exon 3 silent variant c.291G>A. We also identified the heterozygous SDHB exon 2 mutation c.113G>A (p.Arg38Gln) in a PC. These results illustrate that genetic mutations may underlie tumourigenesis in canine PCs and PGLs. The spontaneous nature of these canine diseases and possible association of PGLs with hypoxia in brachycephalic breeds may make them an attractive model for studying the corresponding human tumours., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

miR-210 is a key regulator of response to hypoxia. Pheochromocytomas (PCs) and paragangliomas (PGLs) with germline SDHx or VHL mutations have pseudohypoxic gene expression signatures. We hypothesised that PC/PGLs containing SDHx or VHL mutations, and succinate dehydrogenase (SDH)-deficient gastrointestinal stromal tumours (GISTs), would overexpress miR-210 relative to non-SDH or -VHL-mutated counterparts. miR-210 was analysed by quantitative PCR in i) 39 PC/PGLs, according to genotype (one SDHA, five SDHB, seven VHL, three NF1, seven RET, 15 sporadic, one unknown) and pathology (18 benign, eight atypical, 11 malignant, two unknown); ii) 18 GISTs, according to SDHB immunoreactivity (nine SDH-deficient and nine SDH-proficient) and iii) two novel SDHB-mutant neurosphere cell lines. miR-210 was higher in SDHx- or VHL-mutated PC/PGLs (7.6-fold) compared with tumours without SDHx or VHL mutations (P=0.0016). miR-210 was higher in malignant than in unequivocally benign PC/PGLs (P=0.05), but significance was lost when benign and atypical tumours were combined (P=0.08). In multivariate analysis, elevated miR-210 was significantly associated with SDHx or VHL mutation, but not with malignancy. In GISTs, miR-210 was higher in SDH-deficient (median 2.58) compared with SDH-proficient tumours (median 0.60; P=0.0078). miR-210 was higher in patient-derived neurosphere cell lines containing SDHB mutations (6.5-fold increase) compared with normal controls, in normoxic conditions (P<0.01). Furthermore, siRNA-knockdown of SDHB in HEK293 cells increased miR-210 by 2.7-fold (P=0.001) under normoxia. Overall, our results suggest that SDH deficiency in PC, PGL and GISTs induces miR-210 expression and substantiates the role of aberrant hypoxic-type cellular responses in the development of these tumours.

Germline mutations in the succinate dehydrogenase genes (SDHA, SDHB, SDHC, and SDHD) are established as causes of pheochromocytoma/paraganglioma, renal carcinoma, and gastrointestinal stromal tumor. It has recently been suggested that pituitary adenomas may also be a component of this syndrome. We sought to determine the incidence of SDH mutation in pituitary adenomas. We performed screening immunohistochemistry for SDHB and SDHA on all available pituitary adenomas resected at our institution from 1998 to 2012. In those patients with an abnormal pattern of staining, we then performed SDH mutation analysis on DNA extracted from paraffin-embedded tissue, fresh frozen tissue, and peripheral blood. One of 309 adenomas (0.3%) demonstrated an abnormal pattern of staining, a 30 mm prolactin-producing tumor from a 62-year-old man showing loss of staining for both SDHA and SDHB. Examination of paraffin-embedded and frozen tissues confirmed double-hit inactivating somatic SDHA mutations (c.725&#95;736del and c.989&#95;990insTA). Neither of these mutations was present in the germline. We conclude that, although pathogenic SDH mutation may occur in pituitary adenomas and can be identified by immunohistochemistry, it appears to be a very rare event and can occur in the absence of germline mutation. SDH-deficient pituitary adenomas may be larger and more likely to produce prolactin than other pituitary adenomas. Unless suggested by family history and physical examination, it is difficult to justify screening for SDH mutations in pituitary adenomas. Surveillance programs for patients with SDH mutation may be tailored to include the possibility of pituitary neoplasia; however, this is likely to be a low-yield strategy.

Background: Genetic testing is recommended when the probability of a disease-associated germline mutation exceeds 10%. Germline mutations are found in approximately 25% of individuals with phaeochromcytoma (PCC) or paraganglioma (PGL); however, genetic heterogeneity for PCC/PGL means many genes may require sequencing. A phenotype-directed iterative approach may limit costs but may also delay diagnosis, and will not detect mutations in genes not previously associated with PCC/PGL., Objective: To assess whether whole exome sequencing (WES) was efficient and sensitive for mutation detection in PCC/PGL., Methods: Whole exome sequencing was performed on blinded samples from eleven individuals with PCC/PGL and known mutations. Illumina TruSeq (Illumina Inc, San Diego, CA, USA) was used for exome capture of seven samples, and NimbleGen SeqCap EZ v3.0 (Roche NimbleGen Inc, Basel, Switzerland) for five samples (one sample was repeated). Massive parallel sequencing was performed on multiplexed samples. Sequencing data were called using Genome Analysis Toolkit and annotated using annovar. Data were assessed for coding variants in RET, NF1, VHL, SDHD, SDHB, SDHC, SDHA, SDHAF2, KIF1B, TMEM127, EGLN1 and MAX. Target capture of five exome capture platforms was compared., Results: Six of seven mutations were detected using Illumina TruSeq exome capture. All five mutations were detected using NimbleGen SeqCap EZ v3.0 platform, including the mutation missed using Illumina TruSeq capture. Target capture for exons in known PCC/PGL genes differs substantially between platforms. Exome sequencing was inexpensive (<$A800 per sample for reagents) and rapid (results <5 weeks from sample reception)., Conclusion: Whole exome sequencing is sensitive, rapid and efficient for detection of PCC/PGL germline mutations. However, capture platform selection is critical to maximize sensitivity., (© 2013 John Wiley & Sons Ltd.)

Context: Reports of the coexistence of pituitary adenomas and pheochromocytoma/paraganglioma are uncommon. Recently germline mutations in 2 of the genes encoding succinate dehydrogenase, SDHC and SDHD, were associated with pituitary tumors., Objective: Our aim was to determine whether the development of a pituitary adenoma was associated with SDHA mutation., Patients: A 46-year-old female presented with carotid body paraganglioma (proband). Subsequently the proband's son was diagnosed with a nonfunctioning pituitary macroadenoma at age 30 years., Results: An immunohistochemical analysis of the resected paraganglioma and pituitary adenoma revealed the loss of succinate dehydrogenase subunit B and succinate dehydrogenase subunit A (SDHA) expression in both tumors, with the preservation of staining in nonneoplastic tissue. Mutation analysis showed a novel SDHA mutation (c.1873C>T, p.His625Tyr) in the germline of the proband as well as in the proband's son. In the paraganglioma of the proband, in addition to the germline mutation, a somatic mutation was observed (c.1865G>A, p.Trp622*). In the pituitary adenoma of the proband's son, loss of SDHA immunoreactivity was paradoxically accompanied by loss of the mutant allele., Conclusions: This is the first report of a pituitary adenoma arising in the setting of germline SDHA mutation. The loss of SDHA protein expression in both the paraganglioma (proband) and pituitary adenoma (proband's son) argues strongly for a causative role of SDHA mutation. This report further strengthens the link between pituitary neoplasia and germline SDH mutation. Although pituitary adenomas appear rare among patients carrying SDH subunit mutations, they may have been underrecognized due to the low penetrance of disease and lack of systematic surveillance.

Succinate dehydrogenase-deficient gastrointestinal stromal tumors (SDH-deficient GISTs) are a unique class of GIST defined by negative immunohistochemical staining for succinate dehydrogenase B (SDHB). SDH-deficient GISTs show distinctive clinical and pathologic features including absence of KIT and PDGFRA mutations, exclusive gastric location, common lymph node metastasis, a prognosis not predicted by size and mitotic rate, and indolent behavior of metastases. They may be syndromal with some being associated with the Carney Triad or germline SDHA, SDHB, SDHC, or SDHD mutations (Carney-Stratakis syndrome). It is normally recommended that genetic testing for SDHA, SDHB, SDHC, and SDHD be offered whenever an SDH-deficient GIST is encountered. However, testing for all 4 genes is burdensome and beyond the means of most centers. In this study we performed SDHA mutation and immunohistochemical analyses for SDHA on 10 SDH-deficient GISTs. Three showed negative staining for SDHA, and all of these were associated with germline SDHA mutations. In 2 tumors, 3 novel mutations were identified (p.Gln54X, p.Thr267Met, and c.1663+3G>C), none of which have previously been reported in GISTs or other SDH-associated tumors. Seven showed positive staining for SDHA and were not associated with SDHA mutation. In conclusion, 30% of SDH-deficient GISTs in this study were associated with germline SDHA mutation. Negative staining for SDHA can be used to triage formal genetic testing for SDHA when an SDH-deficient GIST is encountered.

Cancer-associated fibroblasts (CAFs) play a role in tumour initiation and progression, possibly by inducing epithelial-to-mesenchymal transition (EMT), a series of cellular changes that is known to underlie the process of metastasis. The aim of this study was to determine whether CAFs and surrounding normal breast fibroblasts (NBFs) are able to induce EMT markers and functional changes in breast epithelial cancer cells. Matched pairs of CAFs and NBFs were established from fresh human breast cancer specimens and characterised by assessment of CXCL12 levels, α-smooth muscle actin (α-SMA) levels and response to doxorubicin. The fibroblasts were then co-cultured with MCF7 cells. Vimentin and E-cadherin expressions were determined in co-cultured MCF7 cells by immunofluorescence and confocal microscopy as well as by western blotting and quantitative PCR. Co-cultured MCF7 cells were also assessed functionally by invasion assay. CAFs secreted higher levels of CXCL12 and expressed higher levels of α-SMA compared with NBFs. CAFs were also less sensitive to doxorubicin as evidenced by less H2AX phosphorylation and reduced apoptosis on flow cytometric analysis of Annexin V compared with NBFs. When co-cultured with MCF7 cells, there was greater vimentin and less E-cadherin expression as well as greater invasiveness in MCF7 cells co-cultured with CAFs compared with those co-cultured with NBFs. CAFs have the ability to induce a greater degree of EMT in MCF7 cell lines, indicating that CAFs contribute to a more malignant breast cancer phenotype and their role in influencing therapy resistance should therefore be considered when treating breast cancer.

Germline succinate dehydrogenase B (SDHB) mutation causes pheochromocytoma/paraganglioma syndrome type 4 (PGL4). PGL4 is characterized by pheochromocytoma and paraganglioma, type 2 (SDHB negative) gastrointestinal stromal tumors and renal tumors, which are usually classified as carcinoma. We report 4 kindreds with 5 PGL4-associated renal tumors. Four of the tumors occurred before the age of 30 years, 4 were in the left kidney, 3 were in female patients, and 4 demonstrated consistent but previously unrecognized morphology. The tumors were composed of cuboidal cells with bubbly eosinophilic cytoplasm and indistinct cell borders. Many of the cells displayed distinctive cytoplasmic inclusions, which were vacuolated or contained eosinophilic fluid-like material. The cells were arranged in solid nests or in tubules surrounding central spaces. The tumors were well circumscribed or lobulated and frequently showed cystic change. Benign tubules or glomeruli were often entrapped at the edges of the tumors. The fifth tumor lacked these features but displayed sarcomatoid dedifferentiation. Immunohistochemistry for SDHB was completely negative in all 4 available tumors. Death from metastatic disease occurred in the patient with dedifferentiated tumor 1 year after diagnosis, whereas the other 4 tumors were cured by local excision alone (mean follow-up, 11 y; range, 2 to 30 y). We conclude that morphology supported by negative immunohistochemistry for SDHB can be used to identify kindreds with germline SDHB mutations (PGL4 syndrome) presenting with this unique type of renal tumor. These renal tumors appear to have a good prognosis after complete excision unless there is sarcomatoid dedifferentiation.

MicroRNAs (miRNAs) are small RNAs ( approximately 22 bp) that post-transcriptionally regulate protein expression and are found to be differentially expressed in a number of human cancers. There is increasing evidence to suggest that miRNAs could be useful in cancer diagnosis, prognosis, and therapy. We performed miRNA microarray expression profiling on a cohort of 12 benign and 12 malignant pheochromocytomas and identified a number of differentially expressed miRNAs. These results were validated in a separate cohort of ten benign and ten malignant samples using real-time quantitative RT-PCR; benign samples had a minimum follow-up of at least 2 years. It was found that IGF2 as well as its intronic miR-483-5p was over-expressed, while miR-15a and miR-16 were under-expressed in malignant tumours compared with benign tumours. These miRNAs were found to be diagnostic and prognostic markers for malignant pheochromocytoma. The functional role of miR-15a and miR-16 was investigated in vitro in the rat PC12 pheochromocytoma cell line, and these miRNAs were found to regulate cell proliferation via their effect on cyclin D1 and apoptosis. These data indicate that miRNAs play a pivotal role in the biology of malignant pheochromocytoma, and represent an important class of diagnostic and prognostic biomarkers and therapeutic targets warranting further investigation.

Up to 30% of pheochromocytomas and paragangliomas are associated with germline RET, Von Hippel-Lindau (VHL), neurofibromatosis type I (NF1), and succinate dehydrogenase subunits (SDHB, SDHC, and SDHD) mutations. Genetic testing allows familial counseling and identifies subjects at high risk of malignancy (SDHB mutations) or significant multiorgan disease (RET, VHL, or NF1). However, conventional genetic testing for all loci is burdensome and costly. We performed immunohistochemistry for SDHB on 58 tumors with known SDH mutation status. We defined positive as granular cytoplasmic staining (a mitochondrial pattern), weak diffuse as a cytoplasmic blush lacking definite granularity, and negative as completely absent staining in the presence of an internal positive control. All 12 SDH mutated tumors (6 SDHB, 5 SDHD, and 1 SDHC) showed weak diffuse or negative staining. Nine of 10 tumors with known mutations of VHL, RET, or NF1 showed positive staining. One VHL associated tumor showed weak diffuse staining. Of 36 tumors without germline mutations, 34 showed positive staining. One paraganglioma with no known SDH mutation but clinical features suggesting familial disease was negative, and one showed weak diffuse staining. We also performed immunohistochemistry for SDHB on 143 consecutive unselected tumors of which 21 were weak diffuse or negative. As SDH mutations are virtually always germline, we conclude that approximately 15% of all pheochromocytomas or paragangliomas are associated with germline SDH mutation and that immunohistochemistry can be used to triage genetic testing. Completely absent staining is more commonly found with SDHB mutation, whereas weak diffuse staining often occurs with SDHD mutation., (Crown Copyright 2010. Published by Elsevier Inc. All rights reserved.)

The Carney triad (CT) is gastrointestinal stromal tumor (GIST), paraganglioma, and pulmonary chondroma. The GISTs of CT show different clinical, molecular, and morphologic features to usual adult GISTs but are similar to the majority of pediatric GISTs. We postulated that these GISTs would show negative staining for succinate dehydrogenase B (SDHB). We performed SDHB immunohistochemistry on GISTs arising in 5 individuals with CT, 1 child, 7 individuals with GIST in young adulthood including 2 with germline KIT mutations, 3 individuals with neurofibromatosis 1, one 63-year-old female with multifocal gastric epithelioid GIST with lymph node metastases, and 104 consecutive unselected individuals with apparently sporadic GIST. The GISTs and paragangliomas arising in CT, the pediatric GIST, and the multifocal gastric GIST from the 63-year-old showed negative SDHB staining. GISTs from the 7 young adults and 3 with neurofibromatosis were SDHB positive. Of the unselected GISTs, 101 (97%) were positive. One of the negative GISTs arose in a 48-year-old female with previous recurrent multifocal gastric GISTs and the other 2 arose in females also in their 40s with gastric GISTs with epithelioid morphology. We conclude that negative staining for SDHB is characteristic of the GISTs of CT and the subgroup of pediatric GISTs which it resembles. Furthermore, when negative staining occurs in apparently sporadic GISTs in adults, the GISTs show morphologic and clinical features similar to pediatric and CT type GISTs. GISTs may therefore be divided into type 1 (SDHB positive) and type 2 (SDHB negative) subtypes.

Background: The enhancement of metaiodobenzylguanidine single photon emission computed tomography (MIBG SPECT) imaging through the addition of CT images fused with SPECT data (coregistered MIBG SPECT/CT imaging) is new technology that allows direct correlation of anatomical and functional information. We hypothesized that MIBG SPECT/CT imaging would provide additional information and improve diagnostic confidence for the radiological localization of a pheochromocytoma, in particular for patients at high risk of multifocal or recurrent disease., Methods: A retrospective study of all patients investigated by MIBG SPECT/CT at our institution from 2006 to 2008 for a suspected pheochromocytoma was performed. Each case was compared with conventional radiological investigations to determine whether MIBG SPECT/CT was able to improve diagnostic confidence and provide additional diagnostic information compared with conventional imaging alone., Results: Twenty-two patients had MIBG SPECT/CT imaging for a suspected pheochromocytoma. Fourteen patients had positive MIBG SPECT/CT imaging results correlating with imaging by CT or magnetic resonance imaging in all cases. In six cases, MIBG SPECT/CT provided additional information that altered the original radiological diagnosis. Five patients with a pheochromocytoma-associated germline mutation had multifocal disease excluded by MIBG SPECT/CT. Patients without a germline mutation that had positive biochemistry and a solitary lesion with conventional imaging had no diagnostic improvement with MIBG SPECT/CT imaging., Conclusions: MIBG SPECT/CT fusion imaging is a sensitive and specific radiological imaging tool for patients suspected to have pheochromocytoma. The particular strengths of MIBG SPECT/CT are detection of local recurrence, small extra-adrenal pheochromocytomas, multifocal tumors, or the presence of metastatic disease.

Background: Pheochromocytomas are neuroendocrine tumors of chromaffin cell origin which arise from the adrenal medulla and less commonly the extra-adrenal sympathetic paraganglia. Pheochromocytomas are component tumors of the familial syndromes multiple endocrine neoplasia Type 2, von Hippel Lindau disease, Neurofibromatosis Type 1, and the pheochromocytoma/paraganglioma syndromes caused by mutations in the RET, VHL, NF1, SDHB, and SDHD genes, respectively. The aim of this study was to evaluate denaturing high performance liquid chromatography (dHPLC) as a screening tool for the detection of germline mutations within VHL, SDHB, and SDHD in pheochromocytoma patients., Methods: Polymerase chain reaction of all exons of VHL, SDHB, and SDHD genes was performed on leukocyte DNA extracted from stored blood samples of 74 unrelated patients treated for pheochromocytoma. After dHPLC analysis, all samples demonstrating variance were selected for sequencing., Results: Of the 74 patients, 12 mutations and 16 polymorphisms were identified by dHPLC and confirmed on sequencing. More specifically, a total of 5 mutations and 15 polymorphisms were detected in SDHB and 7 mutations and 1 polymorphism were identified in VHL. No SDHD mutations or polymorphisms were identified. By sequencing only dHPLC variants, the total amount of DNA sequencing required was reduced by approximately 88%., Conclusions: dHPLC is an effective screening tool for the detection of germline mutations in SDHB, SDHD, and VHL and has application for diagnostic germline mutation analysis in pheochromocytoma patients.

The management of adrenocortical tumors (ACTs) is complex. The Weiss score is the present most widely used system for ACT diagnosis. An ACT is scored from 0 to 9, with a higher score correlating with increased malignancy. However, ACTs with a score of 3 can be phenotypically benign or malignant. Our objective is to use microarray profiling of a cohort of adrenocortical carcinomas (ACCs) and adrenocortical adenomas (ACAs) to identify discriminatory genes that could be used as an adjunct to the Weiss score. A cohort of Weiss score defined ACCs and ACAs were profiled using Affymetrix HGU133plus2.0 genechips. Genes with high-discriminatory power were identified by univariate and multivariate analyses and confirmed by quantitative real-time reverse transcription PCR and immunohistochemistry (IHC). The expression of IGF2, MAD2L1, and CCNB1 were significantly higher in ACCs compared with ACAs while ABLIM1, NAV3, SEPT4, and RPRM were significantly lower. Several proteins, including IGF2, MAD2L1, CCNB1, and Ki-67 had high-diagnostic accuracy in differentiating ACCs from ACAs. The best results, however, were obtained with a combination of IGF2 and Ki-67, with 96% sensitivity and 100% specificity in diagnosing ACCs. Microarray gene expression profiling accurately differentiates ACCs from ACAs. The combination of IGF2 and Ki-67 IHC is also highly accurate in distinguishing between the two groups and is particularly helpful in ACTs with Weiss score of 3.

Multiple genes and their variants that lend susceptibility to many diseases will play a major role in clinical routine. Genetics-based cost reduction strategies in diagnostic processes are important in the setting of multiple susceptibility genes for a single disease. Head and neck paraganglioma (HNP) is caused by germline mutations of at least three succinate dehydrogenase subunit genes (SDHx). Mutation analysis for all 3 costs approximately US$2,700 per patient. Genetic classification is essential for downstream management of the patient and preemptive management of family members. Utilizing HNP as a model, we wanted to determine predictors to prioritize the most heritable clinical presentations and which gene to begin testing in HNP presentations, to reduce costs of genetic screening. Patients were tested for SDHB, SDHC, and SDHD intragenic mutations and large deletions. Clinical parameters were analyzed as potential predictors for finding germline mutations. Cost reduction was calculated between prioritized gene testing compared with that for all genes. Of 598 patients, 30.6% had SDHx germline mutations: 34.4% in SDHB, 14.2% SDHC, and 51.4% SDHD. Predictors for an SDHx mutation are family history [odds ratio (OR), 37.9], previous pheochromocytoma (OR, 10.9), multiple HNP (OR, 10.6), age

Functional phaeochromocytoma and paraganglioma are rare in children and adolescents. We report a 12-year-old male with bilateral phaeochromocytoma in whom germ line testing identified a novel mutation in the von Hippel Lindau gene. Early age of onset, bilateral phaeochromocytoma and other clinical features should prompt germ line DNA testing for mutations in genes associated with familial phaeochromocytoma and paraganglioma syndromes.

Pheochromocytomas are rare catecholamine-secreting tumors that arise from chromaffin tissue within the adrenal medulla and extra-adrenal sites. Because of the excess secretion of hormones, these tumors often cause debilitating symptoms and a poor quality of life. While medical management plays a significant role in the treatment of pheochromocytoma patients, surgical excision remains the only cure. Improved medical management and surgical techniques and an increased understanding of hereditary disease have improved the outcome of pheochromocytoma patients with benign disease; however, the outcome of patients with malignant disease remains poor. In this review, we discuss the presentation, diagnosis, management, and future directions in the management of this disease.

Objective: To determine the minimal common region of loss on 17p13 in a cohort of adrenocortical carcinomas (ACCs) (defined by a Weiss score > or =3) and adrenocortical adenomas (ACAs) (defined by a Weiss score <3) and subsequently to assess 3 genes in this region that could be involved in adrenocortical tumorigenesis., Summary Background Data: Loss of heterozygosity (LOH) of 17p13 has been demonstrated to occur more frequently in ACCs compared with ACAs., Methods: Using 12 microsatellite markers across 17p13, LOH analysis was performed on 37 paired blood and adrenocortical tumor samples (23 ACC and 14 ACA samples) to determine the minimal common region of loss for ACCs and ACAs. From this minimal region of loss, 3 genes were selected for quantitative real time reverse transcription polymerase chain reaction analysis on 20 ACCs and 30 ACAs., Results: LOH at 17p13 was found in 74% of ACCs compared with 14% of ACAs. There was a 10.4-Mb common minimal region of loss in ACCs whereas no minimal region of loss in ACAs could be demonstrated. Expression of Acyl coenzyme-A dehydrogenase very long chain (ACADVL) and Arachidonate 15-lipoxygenase second type (ALOX15B) was significantly down-regulated in ACCs compared with ACAs whereas there was no difference in expression of Potassium channel tetramerization domain containing 11 (KCTD11) in ACCs and ACAs., Conclusions: We demonstrated a minimal common region of loss of 10.4-Mb on 17p13 in ACCs and within this region, we found that ACADVL and ALOX15B expression are good discriminators between ACCs and ACAs.

Advances in the knowledge of the genetics of phaeochromocytoma have broadened our understanding about the mechanisms of tumorigenesis. Formerly it was believed that 10% of phaeochromocytomas were associated with familial cancer syndromes, but it is now recognised that up to 30% of these tumours may be familial. In particular, attention has been focused on those patients with apparently sporadic presentations where 12-24% of patients have been shown to carry germline mutations indicating hereditary disease. Consideration of genetic testing is now recommended for all apparently sporadic cases and, following the identification of a mutation-positive carrier, the offering of genetic testing to first degree relatives. There is a need for lifelong follow up of affected individuals and asymptomatic mutation-positive carriers, but validation of screening protocols has yet to be determined.

Genetic understanding of pheochromocytoma (PHEO) and paraganglioma (PGL) syndromes has recently expanded with the identification of the involvement of the mitochondrial complex II peptides, namely the succinate dehydrogenase subunit B (SDHB), subunit C (SDHC), and subunit D (SDHD). In patients with PHEO and/or PGL genetic testing for germline mutations in SDHD and SDHB has been recommended, in addition to the PHEO susceptibility genes VHL and RET. After careful clinical assessment of the patient, suspected familial disease may direct the clinician to the appropriate gene for testing. In the absence of obvious features of familial disease, the decision regarding the appropriate gene for testing is more difficult. Such testing can be costly and time consuming, but a rational prioritization of gene testing can streamline the process. Therefore in order to achieve this for apparently sporadic cases we propose a decision matrix based on site of tumor, functionality, and age at presentation.

Context: The identification of mutations in genes encoding peptides of succinate dehydrogenase (SDH) in pheochromocytoma/paraganglioma syndromes has necessitated clear elucidation of genotype-phenotype associations., Objective: Our objective was to determine genotype-phenotype associations in a cohort of patients with pheochromocytoma/paraganglioma syndromes and succinate dehydrogenase subunit B (SDHB) or subunit D (SDHD) mutations., Design, Setting, and Participants: The International SDH Consortium studied 116 individuals (83 affected and 33 clinically unaffected) from 62 families with pheochromocytoma/paraganglioma syndromes and SDHB or SDHD mutations. Clinical data were collected between August 2003 and September 2004 from tertiary referral centers in Australia, France, New Zealand, Germany, United States, Canada, and Scotland., Main Outcome Measures: Data were collected on patients with pheochromocytomas and/or paragangliomas with respect to onset of disease, diagnosis, genetic testing, surgery, pathology, and disease progression. Clinical features were evaluated for evidence of genotype-phenotype associations, and penetrance was determined., Results: SDHB mutation carriers were more likely than SDHD mutation carriers to develop extraadrenal pheochromocytomas and malignant disease, whereas SDHD mutation carriers had a greater propensity to develop head and neck paragangliomas and multiple tumors. For the index cases, there was no difference between 43 SDHB and 19 SDHD mutation carriers in the time to first diagnosis (34 vs. 28 yr, respectively; P = 0.3). However, when all mutation carriers were included (n = 112), the estimated age-related penetrance was different for SDHB vs. SDHD mutation carriers (P = 0.008)., Conclusions: For clinical follow-up, features of SDHB mutation-associated disease include a later age of onset, extraadrenal (abdominal or thoracic) tumors, and a higher rate of malignancy. In contrast, SDHD mutation carriers, in addition to head and neck paragangliomas, should be observed for multifocal tumors, infrequent malignancy, and the possibility of extraadrenal pheochromocytoma.

The discovery of novel mutations in genes encoding succinate dehydrogenase subunits has revealed that familial phaeochromocytomas are much more common than previously thought. Genetic screening should be offered to patients with apparently sporadic phaeochromocytomas and their first-degree relatives. An increasing proportion of phaeochromocytomas present preclinically on genetic testing or as "incidentalomas" on abdominal imaging, rather than with classic symptoms and signs. Clinical suspicion should prompt measurement of plasma levels of free metanephrine or 24-hour urinary catecholamine and metanephrine levels, followed, if positive, by tumour localisation studies. With appropriate perioperative care, surgical management of phaeochromocytomas is safe and effective. Most tumours can be removed laparoscopically.