Gene Summary

Gene:SDHD; succinate dehydrogenase complex subunit D
Aliases: PGL, CBT1, CWS3, PGL1, QPs3, SDH4, cybS, CII-4
Summary:This gene encodes a member of complex II of the respiratory chain, which is responsible for the oxidation of succinate. The encoded protein is one of two integral membrane proteins anchoring the complex to the matrix side of the mitochondrial inner membrane. Mutations in this gene are associated with the formation of tumors, including hereditary paraganglioma. Transmission of disease occurs almost exclusively through the paternal allele, suggesting that this locus may be maternally imprinted. There are pseudogenes for this gene on chromosomes 1, 2, 3, 7, and 18. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Feb 2013]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:succinate dehydrogenase [ubiquinone] cytochrome b small subunit, mitochondrial
Source:NCBIAccessed: 09 March, 2017


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 09 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 09 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: SDHD (cancer-related)

Santi R, Rapizzi E, Canu L, et al.
Potential Pitfalls of SDH Immunohistochemical Detection in Paragangliomas and Phaeochromocytomas Harbouring Germline SDHx Gene Mutation.
Anticancer Res. 2017; 37(2):805-812 [PubMed] Related Publications
BACKGROUND/AIM: Germline mutations in any of the succinate dehydrogenase (SDH) genes result in destabilization of the SDH protein complex and loss of SDHB expression at immunohistochemistry. SDHA is lost together with SDHB in SDHA-mutated tumours, but its expression is retained in tumours with other SDH mutations. We investigated whether SDHA/SDHB immunohistochemistry is able to identify SDH-related tumours in a retrospective case series of phaeochromocytomas (PCCs) and paragangliomas (PGLs).
MATERIALS AND METHODS: SDHA and SDHB immunostaining was performed in 13 SDH gene-mutated tumours (SDHB: n=3; SDHC: n=1; SDHD: n=9) and 16 wild-type tumours. Protein expression by western blot analysis and enzymatic activity were also assessed.
RESULTS: Tumours harbouring SDH gene mutations demonstrated a significant reduction in enzymatic activity and protein expression when compared to wild-type tumours. SDHB immunostaining detected 76.9% of SDH mutated PCCs/PGLs (3/3 SDHB-mutated samples; 1/1 SDHC-mutated sample; 6/9 SDHD-mutated samples). In three SDHD-related tumours with the same mutation (p.Pro81Leu), positive (n=2) or weakly diffuse (n=1) SDHB staining was observed. All wild-type PCCs/PGLs exhibited SDHB immunoreactivity, while immunostaining for SDHA was positive in 93.8% cases and weakly diffuse in one (6.2%). SDHA protein expression was preserved in all tumours with mutations.
CONCLUSION: SDHA and SDHB immunohistochemistry should be interpreted with caution, due to possible false-positive or false-negative results, and ideally in the setting of quality assurance provided by molecular testing. In SDHD mutation, weak non-specific cytoplasmic staining occurs commonly, and this pattern of staining can be difficult to interpret with certainty.

Kedia R, Hansen N, Goldner W
Nuclear Imaging in Metastatic Paraganglioma.
J Nucl Med Technol. 2016; 44(4):251-252 [PubMed] Related Publications
Paragangliomas associated with mutations of the SDHD gene can occasionally result in distant metastasis. Diagnosis can be difficult, and nuclear imaging is used to evaluate the case further. Not all tumors are alike; nuclear avidity may differ. We present a case in which metastatic paraganglioma caused by mutations of the SDHD gene was negative on (123)I-metaiodobenzylguanidine scintigraphy and positive on (111)In-labeled octreotide scintigraphy. This situation presents an opportunity for a novel therapeutic approach toward metastatic paraganglioma using targeted peptide receptor radionuclide therapy.

Pandit R, Khadilkar K, Sarathi V, et al.
Germline mutations and genotype-phenotype correlation in Asian Indian patients with pheochromocytoma and paraganglioma.
Eur J Endocrinol. 2016; 175(4):311-23 [PubMed] Related Publications
BACKGROUND: Genetic aetiology of pheochromocytoma (PCC) and paraganglioma (PGL) is increasingly being studied; however, Asian Indian data on this aspect are scarce.
OBJECTIVE: To study the prevalence of germline mutations and genotype-phenotype correlation in Asian Indian PCC/PGL patients.
DESIGN: In this study, 150 index patients (M:F, 73:77) with PCC/PGL were evaluated. Phenotypic data were collected. Germline mutations in five susceptibility genes (RET, VHL, SDHB, SDHD and SDHC) were tested by sequencing and NF1 was diagnosed according to phenotype.
RESULT: Of the total population, 49 (32.7%) PCC/PGL patients had germline mutations (VHL: 23 (15.3%), RET: 13 (8.7%), SDHB: 9 (6%), SDHD: 2 (1.3%) and NF1: 2 (1.3%)). Amongst the 30 patients with familial and/or syndromic presentation, all had germline mutations (VHL: 14 (46.7%), RET: 13 (43.3%), SDHB: 1 (3.3%) and NF1: 2 (6.7%)). Out of 120 patients with apparently sporadic presentation, 19 (15.8%) had a germline mutation (VHL: 9 (7.5%), SDHB: 8 (6.7%) and SDHD: 2 (1.7%)). Mutation carriers were younger (29.9 ± 14.5 years vs 36.8 ± 14.9; P = 0.01) and had a higher prevalence of bilateral PCC (26.5% vs 2.9%, P < 0.001) and multifocal tumours (12.2% vs 0.96%, P = 0.06). Based on syndromic features, metastasis, location and number of tumours, around 96% mutations in our cohort could be detected by appropriately selected single gene testing.
CONCLUSION: Asian Indians with PCC/PGL differ from Western cohorts in having preponderance of VHL mutations in multifocal tumours and apparently sporadic unilateral PCC. Syndromic presentation, metastasis, location and number of PCC/PGL can be effectively used for guiding genetic prioritisation.

Sundahl N, Van Slycke S, Brusselaers N
A rare case of clinically and biochemically silent giant right pheochromocytoma: case report and review of literature.
Acta Chir Belg. 2016; 116(4):239-242 [PubMed] Related Publications
Non-secreting pheochromocytomas are rare adrenal tumours. We report the case of a clinically and biochemically silent giant pheochromocytoma that presented as bilateral pulmonary embolisms. Successful surgical resection was performed. Multiple endocrine neoplasia 2 syndrome and neurofibromatosis type 1 were clinically excluded. Subsequent DNA analysis of the succinate dehydrogenase complex subunits B and D (SDHB and SDHD), and Von Hippel-Lindau (VHL) genes revealed no mutations.

Kuroda N, Yorita K, Nagasaki M, et al.
Review of succinate dehydrogenase-deficient renal cell carcinoma with focus on clinical and pathobiological aspects.
Pol J Pathol. 2016; 67(1):3-7 [PubMed] Related Publications
Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) was first identified in 2004 and has been integrated into the 2016 WHO classification of RCC. Succinate dehydrogenase (SDH) is an enzyme complex composed of four protein subunits (SDHA, SDHB, SDHC and SDHD). The tumor which presents this enzyme mutation accounts for 0.05 to 0.2% of all renal carcinomas. Multiple tumors may occur in approximately 30% of affected patients. SDHB-deficient RCC is the most frequent, and the tumor histologically consists of cuboidal cells with eosinophilic cytoplasm, vacuolization, flocculent intracytoplasmic inclusion and indistinct cell borders. Ultrastructurally, the tumor contains abundant mitochondria. Immunohistochemically, tumor cells are positive for SDHA, but negative for SDHB in SDHB-, SDHC- and SDHD-deficient RCCs. However, SDHA-deficient RCC shows negativity for both SDHA and SDHB. In molecular genetic analyses, a germline mutation in the SDHB, SDHC or SDHD gene (in keeping with most patients having germline mutations in an SDH gene) has been identified in patients with or without a family history of renal tumors, paraganglioma/pheochromocytoma or gastrointestinal stromal tumor. While most tumors are low grade, some tumors may behave in an aggressive fashion, particularly if they are high nuclear grade, and have coagulative necrosis or sarcomatoid differentiation.

Tessem MB, Bertilsson H, Angelsen A, et al.
A Balanced Tissue Composition Reveals New Metabolic and Gene Expression Markers in Prostate Cancer.
PLoS One. 2016; 11(4):e0153727 [PubMed] Free Access to Full Article Related Publications
Molecular analysis of patient tissue samples is essential to characterize the in vivo variability in human cancers which are not accessible in cell-lines or animal models. This applies particularly to studies of tumor metabolism. The challenge is, however, the complex mixture of various tissue types within each sample, such as benign epithelium, stroma and cancer tissue, which can introduce systematic biases when cancers are compared to normal samples. In this study we apply a simple strategy to remove such biases using sample selections where the average content of stroma tissue is balanced between the sample groups. The strategy is applied to a prostate cancer patient cohort where data from MR spectroscopy and gene expression have been collected from and integrated on the exact same tissue samples. We reveal in vivo changes in cancer-relevant metabolic pathways which are otherwise hidden in the data due to tissue confounding. In particular, lowered levels of putrescine are connected to increased expression of SRM, reduced levels of citrate are attributed to upregulation of genes promoting fatty acid synthesis, and increased succinate levels coincide with reduced expression of SUCLA2 and SDHD. In addition, the strategy also highlights important metabolic differences between the stroma, epithelium and prostate cancer. These results show that important in vivo metabolic features of cancer can be revealed from patient data only if the heterogeneous tissue composition is properly accounted for in the analysis.

Agaimy A
[Succinate dehydrogenase (SDH)-deficient renal cell carcinoma].
Pathologe. 2016; 37(2):144-52 [PubMed] Related Publications
Succinate dehydrogenase (SDH) represents a type II mitochondrial complex related to the respiratory chain and Krebs cycle. The complex is composed of four major subunits, SDHA, SDHB, SDHC and SDHD. The oncogenic role of this enzyme complex has only recently been recognized and the complex is currently considered an important oncogenic signaling pathway with tumor suppressor properties. In addition to the familial paraganglioma syndromes (types 1-5) as prototypical SDH-related diseases, many other tumors have been defined as SDH-deficient, in particular a subset of gastrointestinal stromal tumors (GIST), rare hypophyseal adenomas, a subset of pancreatic neuroendocrine neoplasms (recently added) and a variety of other tumor entities, the latter mainly described as rare case reports. As a central core subunit responsible for the integrity of the SDH complex, the expression of SDHB is lost in all SDH-deficient neoplasms irrespective of the specific SDH subunit affected by a genetic mutation in addition to concurrent loss of the subunit specifically affected by genetic alteration. Accordingly, all SDH-deficient neoplasms are by definition SDHB-deficient. The SDH-deficient renal cell carcinoma (RCC) has only recently been well-characterized and it is included as a specific subtype of RCC in the new World Health Organization (WHO) classification published in 2016. In this review, the major clinicopathological, immunohistochemical and genetic features of this rare disease entity are presented and discussed in the context of the broad differential diagnosis.

Cheng Y, Zhang Z, Zhu H, et al.
[Clinicopathologic features of succinate dehydrogenase-deficient gastrointestinal stromal tumor].
Zhonghua Bing Li Xue Za Zhi. 2016; 45(3):153-8 [PubMed] Related Publications
OBJECTIVE: To investigate clinicopathologic features of succinate dehydrogenase-deficient gastrointestinal stromal tumors (SDH-deficient GIST).
METHODS: Immunohistochemical EnVision technique was used to assess the expression of succinate dehydrogenase subunit B (SDHB) in 192 cases of GIST. Cases of SDH-deficient GIST were further evaluated for the presence of CKIT exons 9, 11, 13 and 17 mutations and PDGFRA exons 12 and 18 mutations with clinical followed-up data.
RESULTS: Seven of the 192 cases showed SDHB-deficiency (3.6%, 7/192). The patients ranged in age from 35 to 84 years (median=56 years; mean=60 years). Four were male and three were female. Six tumors involved stomach and one involved mesentery. Histopathologic features of SDHB-deficient GIST included four cases of mixed-cell type and three of epithelioid cell type. The tumors commonly involved muscularis propria of the stomach as multiple nodules, creating a plexiform pattern. The tumors had high cellularity with cytoplasmic vacuolization. Five cases developed lymph node metastases including one also metastasizing to liver and pancreas. Two cases showed no evidence of metastasis. None of the 7 cases of the SDHB-deficient GIST had CKIT exons 9, 11, 13 and 17 mutations and PDGFRA exons 12 and 18 mutations. Three of the seven SDHB-deficient GIST cases had followed-up data: two did not recur and one died after 24 months of surgery of unknown cause.
CONCLUSION: SDHB-deficient GIST has characteristic clinicopathologic features with wide-type CKIT gene and a favorable prognosis.

Osinga TE, Xekouki P, Nambuba J, et al.
SDH Subunit Mutation Status in Saliva: Genetic Testing in Patients with Pheochromocytoma.
Horm Metab Res. 2016; 48(4):247-50 [PubMed] Related Publications
Germline mutations occur in up to 30-40% of pheochromocytoma/paraganglioma, with mutations in the succinate dehydrogenase (SDH) subunits B (SDHB) and D (SDHD) being the most common. Blood samples are favored for obtaining high quality DNA, however, leukocytes can also be obtained by collecting saliva. The aim of this study was to determine whether SDHB and SDHD gene mutations in patients with pheochromocytoma/paraganglioma could be determined using a salivary sample. Paired blood and salivary samples were collected from 30 patients: 9 SDHB mutation positive, 13 with a SDHD mutation, and 8 without any SDHx mutations. The Oragene DISCOVER kit was used to collect and extract DNA from saliva. Blood DNA was extracted from EDTA blood samples. The DNA purification and concentration were measured by spectrophotometry. The 8 exons of SDHB and the 4 exons of SDHD were amplified and sequenced by PCR-based bidirectional Sanger sequencing. Total DNA yields from blood DNA were similar to those obtained from saliva DNA [mean (±SD) saliva vs. blood DNA concentration 514.6 (±580.8) ng/µl vs. 360.9 (±262.7) ng/µl; p=0.2)]. The purity of the saliva DNA samples was lower than that of blood [mean OD260/OD280 ratio 1.78 (±0.13) vs. 1.87 (±0.04); p=0.001, respectively], indicating more protein contamination in the saliva-extracted DNA. This study shows that salivary DNA collected from patients with pheochromocytoma/paraganglioma is a good alternative for extraction of genomic DNA for its high DNA concentration and acceptable purity and can be used as an alternative to blood derived DNA in screening for SDHB and SDHD mutations.

Guo T, Gu C, Chen X, et al.
Inhibition of succinate dehydrogenase sensitizes cyclin E-driven ovarian cancer to CDK inhibition.
Biofactors. 2016 Mar-Apr; 42(2):171-8 [PubMed] Related Publications
AIM: High-grade serous ovarian cancer (HGS-OvCa) is characterized by widespread CCNE1 amplification. Current treatments lack specificity to target Cyclin E-driven OvCa.
METHODS: By in silico analysis of the TCGA OvCa dataset we searched association between genes involved in glucose metabolism and cell cycle control. Metabolic shift was studied in Cyclin E-driven OvCa cells treated with CDK inhibition (CDKi). Genetic and pharmaceutical inhibition of succinate dehydrogenase (SDH) was tested in combination with CDKi.
RESULTS: OvCa patients with CCNE1 amplification could be divided by concomitant SDHA amplification. A2780 OvCa cells were similar to the Cyclin E-driven and SDHA neutral genotype. CDKi in A2780 cells using Dinaciclib resulted in compensatory enhancement of tricarboxylicacid cycle (TCA) cycle activity. Combined blockade of CDK and SDH, both genetically and pharmaceutically, showed synergy and resulted in inhibited proliferation, migration, invasion and migration in A2780 cells. The combined inhibition did not further alter cell cycle population, but induced apoptosis of A2780 cells.
CONCLUSION: Cyclin E-driven OvCa cells appeared addicted to glucose metabolism via TCA. Combined CDKi with modalities targeting TCA, like SDHA inhibition showed promising effects for this genotype.

Knie B, Plotkin M, Zschieschang P, et al.
A family with pheochromocytoma-paraganglioma inherited tumour syndrome. Serial 18F-DOPA PET/CT investigations.
Nuklearmedizin. 2016; 55(1):34-40 [PubMed] Related Publications
AIM: Hereditary pheochromocytoma-paraganglioma syndromes are characterized by multiple pheochromocytomas (PCC) and paragangliomas (PGLs), inherited in an autosomal dominant manner. Early detection and removal of tumours may prevent or minimize complications related to mass effects and malignant transformation. Having confirmed the diagnosis, it is important to localize the tumours and reveal their extent preoperatively. This study aimed to introduce 18F-DOPA PET/CT as a highly sensitive non-invasive diagnostic tool for early detection of mass lesions in patients with pheochromocytoma-paraganglioma inherited tumour syndrome and to report about its impact on patient management.
PATIENTS, METHODS: We are currently supervising one of the largest documented families in Germany with genetically determined SDHD gene mutation. We performed 18F-DOPA PET/CT in order to detect tumours in asymptomatic gene carriers and enable subsequent surgical therapy.
RESULTS: In seven patients undergoing 12 18F-DOPA PET/CT scans 17 lesions have been detected. Three of these lesions, located in the head and neck region, have had no morphologic correlate in CT and one had also no morphologic correlate in MRI. Of the six histologically analyzed lesions five have been tumors (PGL or PCC) and one has been a nodular hyperplasia. This means the 18F-DOPA PET/CT scan in our study group had a sensitivity of 83%. 18F-DOPA PET/CT investigations lead to change in the management in 5/7 studied patients (70%).
CONCLUSION: The benefits of PET/CT in detection of pheochromocytoma and paraganglioma are well documented, but we are the first to use this technique for screening of a rare hereditary disease (estimated prevalence 0.3/100 000).

Jiang Q, Zhang Y, Zhou YH, et al.
A novel germline mutation in SDHA identified in a rare case of gastrointestinal stromal tumor complicated with renal cell carcinoma.
Int J Clin Exp Pathol. 2015; 8(10):12188-97 [PubMed] Free Access to Full Article Related Publications
Succinate dehydrogenase (SDH), which is located on the mitochondrial inner membrane, is essential to the Krebs cycle. Mutations of the SDH gene are associated with many tumors, such as renal cell carcinoma, wild type gastrointestinal stromal tumors (WT GISTs) and hereditary paragangliomas/pheochromocytomas. Herein we present a rare case diagnosed as a WT GIST complicated with a renal chromophobe cell tumor and detected a novel germline heterozygous mutation (c.2T>C: p.M1T) in the initiation codon of the SDHA gene. We also conduct a preliminary exploration for the mechanism of reduced expression of SDHB without mutation of SDHB gene. Our case enriches the mutation spectrum of the SDH gene. After reviewing previous studies, we found it to be the first case diagnosed as a WT GIST complicated with a synchronous renal chromophobe cell tumor and identified a novel germline heterozygous mutation. It was also the second reported case of a renal cell carcinoma associated with an SDHA mutation.

Gong Q, Zhang W, Li H, et al.
[Succinate dehydrogenase deficient gastrointestinal stromal tumor: a clinicopathologic analysis of eight cases].
Zhonghua Bing Li Xue Za Zhi. 2015; 44(10):709-13 [PubMed] Related Publications
OBJECTIVE: To study the clinicopathologic features, diagnosis and differential diagnosis of succinate dehydrogenase (SDH) deficient gastrointestinal stromal tumors (GISTs) as a unique tumor subtype.
METHODS: SDHB and SDHA immunohistochemistry was performed in 120 gastric GISTs, in addition to CD117, DOG-1, CD34, smooth muscle actin (SMA), desmin, S-100 protein, cytokeratin (CK) and Ki-67. Subset of the cases was further evaluated for the presence of mutations in CKIT exons 9, 11, 13 and 17 mutations and platelet derived growth factor receptor alpha(PDGFRA) exons 12 and 18.
RESULTS: Eight of 120 (6.6%) GIST cases were found SDH-deficient including 3 male and 5 female patients (median age of 36.2 years; ranging 16 to 65 years of age). The tumors involved antrum (6 cases), lesser curvature (1 case) and fundus (1 case). Macroscopically, the dominant tumor masses varied from 3 to 10 cm in diameter with a multinodular or plexiform pattern involving the gastric wall. Microscopically,tumor cells had predominantly epithelioid morphology, with occasional mixed spindle cell nodules. Lymphovascular invasion was identified in 5 cases. Immunohistochemistry for SDHB was negative in all 8 cases, and SDHA was negative in 5 cases. All 8 SDHB negative cases also expressed CD117, DOG-1 and CD34, but were negative for SMA, desmin, S-100 and CK. All 8 cases were found to have wild-type CKIT and PDGFRA genes. Available clinical follow-up were obtained in 7 cases, ranging from 2 to 60 months (median follow-up 23.3 months), and all patient were alive. Three cases were found to have liver metastases at their first diagnosis, and one developed omental and mesenteric metastases in 17 months.
CONCLUSIONS: SDH-deficient GIST is a distinct subtype of GIST, with a predilection to occur in young and female patients. Characteristic pathological findings include multinodular gastric wall involvement, epithelioid cell morphology, frequently lymphovascular invasion with occasional lymph node and liver metastases, but an overall indolent clinical behavior. Immunohistochemistry for SDHB is required for the diagnosis.

Archier A, Varoquaux A, Garrigue P, et al.
Prospective comparison of (68)Ga-DOTATATE and (18)F-FDOPA PET/CT in patients with various pheochromocytomas and paragangliomas with emphasis on sporadic cases.
Eur J Nucl Med Mol Imaging. 2016; 43(7):1248-57 [PubMed] Related Publications
PURPOSE: Pheochromocytomas/paragangliomas (PHEOs/PGLs) overexpress somatostatin receptors and recent studies have already shown excellent results in the localization of these tumors using (68)Ga-labeled somatostatin analogs ((68)Ga-DOTA-SSA), especially in patients with germline succinate dehydrogenase subunit B gene (SDHB) mutations and head and neck PGLs (HNPGLs). The value of (68)Ga-DOTA-SSA has to be established in sporadic cases, including PHEOs. Thus, the aim of this study was to compare (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging in patients with various PHEOs/PGLs with a special emphasis on sporadic cases, including those located in the adrenal gland.
DESIGN: (68)Ga-DOTATATE, (18)F-FDOPA PET/CT, and conventional imaging (contrast-enhanced CT and MRI with MR angiography sequences) were prospectively performed in 30 patients (8 with SDHD mutations, 1 with a MAX mutation and 21 sporadic cases) with PHEO/PGL at initial diagnosis or relapse.
RESULTS: The patient-based sensitivities were 93 % (28/30), 97 % (29/30), and 93 % (28/30) for (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging, respectively. The lesion-based sensitivities were 93 % (43/46), 89 % (41/46), and 76 % (35/46) for (68)Ga-DOTATATE PET/CT, (18)F-FDOPA PET/CT, and conventional imaging respectively (p = 0.042). (68)Ga-DOTATATE PET/CT detected a higher number of HNPGLs (30/30) than (18)F-FDOPA PET/CT (26/30; p = 0.112) and conventional imaging (24/30; p = 0.024). (68)Ga-DOTATATE PET/CT missed two PHEOs of a few millimeters in size and a large recurrent PHEO. One lesion was considered false-positive on (68)Ga-DOTATATE PET/CT and corresponded to a typical focal lesion of fibrous dysplasia on MRI. Among the 11 lesions missed by conventional imaging, 7 were detected by conventional imaging with knowledge of the PET results (4 HNPGLs, 2 LNs, and 1 recurrent PHEO).
CONCLUSION: (68)Ga-DOTATATE PET/CT is the most sensitive tool in the detection of HNPGLs, especially SDHD-related tumors, which may be very small and fail to concentrate sufficient (18)F-FDOPA. The present study further expands the use of (68)Ga-DOTATATE for all patients with HNPGLs, regardless of their genotype. (68)Ga-DOTATATE PET/CT may be inferior to (18)F-FDOPA PET/CT in the detection PHEOs.

den Brave PS, Balm AJ, Balm R
[The carotid body paraganglioma: a rare swelling of the neck].
Ned Tijdschr Geneeskd. 2015; 159:A9230 [PubMed] Related Publications
BACKGROUND: A carotid body paraganglioma is a rare tumour of the neck, which occurs at the level of the carotid bifurcation.
CASE DESCRIPTION: A 52-year-old man was referred with a 10-year history of a swelling on the right side of his neck. Imaging revealed that this was a carotid body paraganglioma. The tumour showed no hormonal activity and there were no other paraganglioma localisations. We removed the tumour surgically, and histological examination confirmed the diagnosis of paraganglioma. Genetic investigation revealed that the patient was a carrier of a mutation in the succinate dehydrogenase complex, subunit D (SDHD) gene.
CONCLUSION: A paraganglioma of the carotid body is usually benign and slow-growing. It is familial in about 50% of cases, with a characteristic mutation in the SDHD-gene. Surgical removal is often the treatment of choice. If there is too high a risk of injury due to surgery, or in cases of inoperability, a "wait and see" policy with radiological follow-up is implemented. Diagnostics, treatment and follow-up demand a multidisciplinary approach.

Yukina MY, Troshina EA, Beltsevich DG
[Hereditary pheochromocytoma-associated syndromes. Part 1].
Ter Arkh. 2015; 87(9):102-5 [PubMed] Related Publications
Pheochromocytoma (PCC)/paraganglioma is a catecholamine-secreting tumor of the paraganglion. The hereditary variants of PCC have been previously considered to occur in 10% of cases. The latest researches have clearly demonstrated that the hereditary cause of chromaffin tumors is revealed in a much larger number of patients. There have been the most investigated NF, RET, VHL, SDHD, SDHC, and SDHB gene mutations. New EGLN1/PHD2, KIF1B, SDH5/SDHAF2, IDH1, TMEM127, SDHA, MAX, and HIF2A gene mutations have been recently discovered. This review describes new ideas of the genetic bases of PCC. The authors discuss criteria for patient referral for genetic examination on the basis of the phenotypic.manifestations of mutations, such as a malignant course, bilateral adrenal lesion, and age at disease manifestations. Recommendations are determined for carriers to screen for the components of hereditary pathology.

Scollo C, Russo M, De Gregorio L, et al.
A novel RET gene mutation in a patient with apparently sporadic pheochromocytoma.
Endocr J. 2016; 63(1):87-91 [PubMed] Related Publications
Pheochromocytoma (Pheo) is a chromaffin tumor arising from the adrenal medulla. The recent discovery of new germline mutations in RET, SDHA, SDHB, SDHC, SDHD, VHL, NF1, TMEM127, MAX genes, increased the rate of genetic disease from 10% to 28% in patients with apparently sporadic tumor. RET germline mutations cause multiple endocrine neoplasia type 2 syndrome (MEN 2A) characterized by complete penetrance of medullary thyroid cancer (MTC), and lower prevalence of Pheo and hyperparathyroidism. We describe the genetic etiology of an apparently sporadic case of monolateral Pheo in a 42-year-old male patient. A new (not previously reported) MEN 2A-associated germline RET mutation located in exon 11 (Glu632Gly, caused by an A>G point mutation at position 1895 of the RET cDNA) was found in the patient but not in his living first-degree relatives. This observation increases the number of possible germline RET mutations. Genotype-phenotype correlation of this new genetic alteration is unknown, but this rare mutation is probably associated with a low risk for MTC (usually the first tumor diagnosed in MEN 2A syndrome) and with the development of Pheo before the onset of MTC. Since we expect MTC to occur in our patient, strict follow-up is mandatory. Our findings emphasize the relevance of genetic testing in patients with Pheo, especially when the clinical presentation (family history, young age at diagnosis, multiple locations, malignant lesions, and bilateralism) is suggestive.

Lussey-Lepoutre C, Bellucci A, Morin A, et al.
In Vivo Detection of Succinate by Magnetic Resonance Spectroscopy as a Hallmark of SDHx Mutations in Paraganglioma.
Clin Cancer Res. 2016; 22(5):1120-9 [PubMed] Related Publications
PURPOSE: Germline mutations in genes encoding mitochondrial succinate dehydrogenase (SDH) are found in patients with paragangliomas, pheochromocytomas, gastrointestinal stromal tumors, and renal cancers. SDH inactivation leads to a massive accumulation of succinate, acting as an oncometabolite and which levels, assessed on surgically resected tissue are a highly specific biomarker of SDHx-mutated tumors. The aim of this study was to address the feasibility of detecting succinate in vivo by magnetic resonance spectroscopy.
EXPERIMENTAL DESIGN: A pulsed proton magnetic resonance spectroscopy ((1)H-MRS) sequence was developed, optimized, and applied to image nude mice grafted with Sdhb(-/-) or wild-type chromaffin cells. The method was then applied to patients with paraganglioma carrying (n = 5) or not (n = 4) an SDHx gene mutation. Following surgery, succinate was measured using gas chromatography/mass spectrometry, and SDH protein expression was assessed by immunohistochemistry in resected tumors.
RESULTS: A succinate peak was observed at 2.44 ppm by (1)H-MRS in all Sdhb(-/-)-derived tumors in mice and in all paragangliomas of patients carrying an SDHx gene mutation, but neither in wild-type mouse tumors nor in patients exempt of SDHx mutation. In one patient, (1)H-MRS results led to the identification of an unsuspected SDHA gene mutation. In another case, it helped define the pathogenicity of a variant of unknown significance in the SDHB gene.
CONCLUSIONS: Detection of succinate by (1)H-MRS is a highly specific and sensitive hallmark of SDHx mutations. This noninvasive approach is a simple and robust method allowing in vivo detection of the major biomarker of SDHx-mutated tumors.

Ozluk Y, Taheri D, Matoso A, et al.
Renal carcinoma associated with a novel succinate dehydrogenase A mutation: a case report and review of literature of a rare subtype of renal carcinoma.
Hum Pathol. 2015; 46(12):1951-5 [PubMed] Related Publications
Renal cell carcinoma (RCC) linked to germline mutation of succinate dehydrogenase subunits A, B, C, and D (SDHA, SDHB, SDHC, and SDHD, respectively) has been recently included as a provisional entity in the 2013 International Society of Urological Pathology Vancouver classification. Most SDH-deficient tumors show SDHB mutation, with only a small number of RCC with SDHC or SDHD having been reported to date. Only one case of SDH-deficient renal carcinoma known to be SDHA mutated has been previously reported. Here we report an additional RCC harboring an SDHA mutation occurring in a 62-year-old man with right flank pain and nodal metastasis. The tumor was characterized by an infiltrative pattern with solid, acinar, and papillary components. Loss of SDHA and SDHB protein by immunohistochemistry confirmed the diagnosis. Hybrid capture-based comprehensive genomic profiling identified 3 genomic alterations in tumor tissue: (i) a novel single-nucleotide splice site deletion in SDHA gene, (ii) single-nucleotide deletion in NF2 gene, and (iii) EGFR gene amplification of 19 copies. This is the second report of SDHA-mutated RCC. With increased awareness, this rare tumor can be recognized on the basis of distinctive morphology and confirmation by immunohistochemistry and genomic profiling.

Dong G, He X, Chen Y, et al.
Genetic variations in genes of metabolic enzymes predict postoperational prognosis of patients with colorectal cancer.
Mol Cancer. 2015; 14:171 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Genetic alterations in tricarboxylic acid (TCA) cycle metabolic enzymes were recently linked to various cancers. However, the associations of single nucleotide polymorphisms (SNPs) in genes of these enzymes have not been well studied.
METHODS: We genotyped 16 SNPs from 7 genes encoding TCA cycle metabolic enzymes in 697 colorectal carcinoma (CRC) patients receiving surgical resection and analyzed their associations with clinical outcomes by multivariate Cox proportional hazard model. Then, the significant results were validated in another cohort of 256 CRC patients.
RESULTS: We identified 4 SNPs in 2 genes had significant associations with CRC death risk and 5 SNPs in 3 genes had significant associations with CRC recurrence risk. Similar significant results were confirmed for rs4131826 in SDHC gene, rs544184 in SDHD gene and rs12071124 in FH gene in a validation cohort. Further analysis indicated that unfavorable genotypes exhibited a significant cumulative effect on overall and recurrence-free survival in a dose-dependent manner. Moreover, survival tree analysis indicated that SNP rs4131826 in SDHC gene and SNP rs12071124 in FH gene were the primary factors contributing to the different overall survival time and recurrence-free survival time of CRC patients, respectively. Immunohistochemical analysis further validated the effect of rs4131826 and rs544184 on expression of SDHC and SDHD in tissue samples.
CONCLUSIONS: Our study suggests that SNPs in TCA cycle metabolic enzymes might be significantly associated with clinical outcomes in Chinese population diagnosed with CRC. Further functional and validated studies are warranted to expend our results to clinical utility.

Shiwa T, Oki K, Yoneda M, et al.
A Patient with an Extra-adrenal Pheochromocytoma and Germ-line SDHB Mutation Accompanied by an Atypical Meningioma.
Intern Med. 2015; 54(18):2355-60 [PubMed] Related Publications
The gene succinate dehydrogenase subunit B (SDHB) encodes a protein comprising part of the mitochondrial complex II, which links the Krebs cycle and the electron-transport chain. Heterozygous germ-line SDHB mutations causes familial pheochromocytoma-paraganglioma syndrome and has also been linked to gastrointestinal stromal tumors, as well as renal cell carcinomas. We herein report a patient with a germ-line SDHB mutation who presented with an atypical meningioma that was identified as originating from a somatic SDHB mutation. The 41-year-old man, who had a surgical history of extra-adrenal pheochromocytoma at 23 years of age, recently developed gait disorder and hypertension. At the radiological examination, a tumor was detected in the cervical spinal cord at the C6-7 intervertebral level. The pathological findings of the isolated tumor were atypical meningioma assessed as grade II according to the World Health Organization criteria. Inherited neoplasia syndrome was suspected because of the patient's history of early-onset extra-adrenal pheochromocytoma and the development of meningioma. We therefore performed molecular genetic analyses. A direct sequence analysis revealed a heterozygous germ-line frameshift mutation in SDHB, specifically an 11-nucleotide deletion, c.305-315delCAATGAACATC, in exon 4, resulting in a frameshift p.A102EfsX12. Additionally, the sequence analysis of the tumor DNA revealed only a mutated allele with a frameshift mutation in the germ-line SDHB. Our findings suggest that SDHB plays an important role in the pathogenesis of meningiomas as well as pheochromocytomas. Therefore, a differential diagnosis for metastatic pheochromocytoma and other new onset tumors, including meningioma, particularly in patients with germ-line SDHB mutations and a previous history of pheochromocytoma should be carefully made.

Scholz SL, Horn S, Murali R, et al.
Analysis of SDHD promoter mutations in various types of melanoma.
Oncotarget. 2015; 6(28):25868-82 [PubMed] Free Access to Full Article Related Publications
OBJECTIVES: Recently, recurrent mutations in regulatory DNA regions, such as promoter mutations in the TERT gene were identified in melanoma. Subsequently, Weinhold et al. reported SDHD promoter mutations occurring in 10% of melanomas and being associated with a lower overall survival rate. Our study analyzes the mutation rate and clinico-pathologic associations of SDHD promoter mutations in a large cohort of different melanoma subtypes.
METHODS: 451 melanoma samples (incl. 223 non-acral cutaneous, 38 acral, 33 mucosal, 43 occult, 43 conjunctival and 51 uveal melanoma) were analyzed for the presence of SDHD promoter mutations by Sanger-sequencing. Statistical analysis was performed to screen for potential correlations of SDHD promoter mutation status with various clinico-pathologic criteria.
RESULTS: The SDHD promoter was successfully sequenced in 451 tumor samples. ETS binding site changing SDHD promoter mutations were identified in 16 (4%) samples, of which 5 mutations had not been described previously. Additionally, 5 point mutations not located in ETS binding elements were identified. Mutations in UV-exposed tumors were frequently C>T. One germline C>A SDHD promoter mutation was identified. No statistically significant associations between SDHD promoter mutation status and various clinico-pathologic variables or overall patient survival were observed.
CONCLUSIONS: Melanomas harbor recurrent SDHD promoter mutations, which occur primarily as C>T alterations in UV-exposed melanomas. In contrast to the initial report and promoter mutations in the TERT gene, our analysis suggests that SDHD promoter mutations are a relatively rare event in melanoma (4% of tumors) of unclear clinical and prognostic relevance.

Benn DE, Robinson BG, Clifton-Bligh RJ
15 YEARS OF PARAGANGLIOMA: Clinical manifestations of paraganglioma syndromes types 1-5.
Endocr Relat Cancer. 2015; 22(4):T91-103 [PubMed] Free Access to Full Article Related Publications
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.

Lee CH, Cheung CY, Chow WS, et al.
Genetics of Apparently Sporadic Pheochromocytoma and Paraganglioma in a Chinese Population.
Horm Metab Res. 2015; 47(11):833-8 [PubMed] Related Publications
Identification of germline mutation in patients with apparently sporadic pheochromocytomas and paragangliomas is crucial. Clinical indicators, which include young age, bilateral or multifocal, extra-adrenal, malignant, or recurrent tumors, predict the likelihood of harboring germline mutation in Caucasian subjects. However, data on the prevalence of germline mutation, as well as the applicability of these clinical indicators in Chinese, are lacking. We conducted a cross-sectional study at a single endocrine tertiary referral center in Hong Kong. Subjects with pheochromocytomas and paragangliomas were evaluated for the presence of germline mutations involving 10 susceptibility genes, which included NF1, RET, VHL, SDHA, SDHB, SDHC, SDHD, TMEM 127, MAX, and FH genes. Clinical indicators were assessed for their association with the presence of germline mutations. Germline mutations, 2 being novel, were found in 24.4% of the 41 Chinese subjects recruited and 11.4% among those with apparently sporadic presentation. The increasing number of the afore-mentioned clinical indicators significantly correlated with the likelihood of harboring germline mutation in one of the 10 susceptibility genes. (r=0.757, p=0.026). The presence of 2 or more clinical indicators should prompt genetic testing for germline mutations in Chinese subjects. In conclusion, our study confirmed that a significant proportion of Chinese subjects with apparently sporadic pheochromocytoma and paraganglioma harbored germline mutations and these clinical indicators identified from Caucasians series were also applicable in Chinese subjects. This information will be of clinical relevance in the design of appropriate genetic screening strategies in Chinese populations.

Niemeijer ND, Papathomas TG, Korpershoek E, et al.
Succinate Dehydrogenase (SDH)-Deficient Pancreatic Neuroendocrine Tumor Expands the SDH-Related Tumor Spectrum.
J Clin Endocrinol Metab. 2015; 100(10):E1386-93 [PubMed] Related Publications
CONTEXT: Mutations in genes encoding the subunits of succinate dehydrogenase (SDH) can lead to pheochromocytoma/paraganglioma formation. However, SDH mutations have also been linked to nonparaganglionic tumors.
OBJECTIVE: The objective was to investigate which nonparaganglionic tumors belong to the SDH-associated tumor spectrum.
DESIGN: This was a retrospective cohort study.
SETTING: The setting was a tertiary referral center.
PATIENTS: Patients included all consecutive SDHA/SDHB/SDHC and SDHD mutation carriers followed at the Department of Endocrinology of the Leiden University Medical Center who were affected by non-pheochromocytoma/paraganglioma solid tumors.
MAIN OUTCOME MEASURES: Main outcome measures were SDHA/SDHB immunohistochemistry, mutation analysis, and loss of heterozygosity analysis of the involved SDH-encoding genes.
RESULTS: Twenty-five of 35 tumors (from 26 patients) showed positive staining on SDHB and SDHA immunohistochemistry. Eight tumors showed negative staining for SDHB and positive staining for SDHA: a pancreatic neuroendocrine tumor, a macroprolactinoma, two gastric gastrointestinal stromal tumors, an abdominal ganglioneuroma, and three renal cell carcinomas. With the exception of the abdominal ganglioneuroma, loss of heterozygosity was detected in all tumors. A prolactinoma in a patient with a germline SDHA mutation was the only tumor immunonegative for both SDHA and SDHB. Sanger sequencing of this tumor revealed a somatic mutation (p.D38V) as a likely second hit leading to biallelic inactivation of SDHA. One tumor (breast cancer) showed heterogeneous SDHB staining, positive SDHA staining, and retention of heterozygosity.
CONCLUSIONS: This study strengthens the etiological association of SDH genes with pituitary neoplasia, renal tumorigenesis, and gastric gastrointestinal stromal tumors. Furthermore, our results indicate that pancreatic neuroendocrine tumor also falls within the SDH-related tumor spectrum.

Rich T, Jackson M, Roman-Gonzalez A, et al.
Metastatic sympathetic paraganglioma in a patient with loss of the SDHC gene.
Fam Cancer. 2015; 14(4):615-9 [PubMed] Related Publications
Mutation of the genes encoding the succinate dehydrogenase (SDH) subunits A, B, C, or D, or the SDHAF2 protein, cause the SDHx-hereditary paraganglioma syndromes. Hereditary susceptibility to metastatic sympathetic pheochromocytomas and paragangliomas is most commonly due to germline mutations in the SDHB gene. Individuals with SDHD mutations occasionally present with metastatic disease, while conversely malignant paragangliomas are rarely observed in SDHC carriers. A 43 year-old woman presented with an abdominal paraganglioma metastatic to the skeleton and multiple lymph nodes. The tumor produced excessive amounts of noradrenaline causing hypertension and symptoms of catecholamine excess. The patient underwent surgical resection of the primary tumor and lymph node metastases. Loss of SDHB protein expression in the primary tumor was demonstrated by immunohistochemistry. Germline sequencing and deletion testing revealed a large allelic deletion of exons 1-6 in SDHC, and no mutations or deletions were detected in SDHB or SDHD. The patient's mother died because of kidney cancer. Hereditary pheochromocytomas and paragangliomas may be associated with a deletion of the SDHC gene. These patients may present with malignant sympathetic paragangliomas.

Baysal BE, Maher ER
15 YEARS OF PARAGANGLIOMA: Genetics and mechanism of pheochromocytoma-paraganglioma syndromes characterized by germline SDHB and SDHD mutations.
Endocr Relat Cancer. 2015; 22(4):T71-82 [PubMed] Related Publications
Pheochromocytomas and paragangliomas (PPGL) are rare neuroendocrine neoplasms that derive from small paraganglionic tissues which are located from skull base to the pelvic floor. Genetic predisposition plays an important role in development of PPGLs. Since the discovery of first mutations in the succinate dehydrogenase D (SDHD) gene, which encodes the smallest subunit of mitochondrial complex II (SDH), genetic studies have revealed a major role for mutations in SDH subunit genes, primarily in SDHB and SDHD, in predisposition to both familial and non-familial PPGLs. SDH-mutated PPGLs show robust expression of hypoxia induced genes, and genomic and histone hypermethylation. These effects occur in part through succinate-mediated inhibition of α-ketoglutarate-dependent dioxygenases. However, details of mechanisms by which SDH mutations activate hypoxic pathways and trigger subsequent neoplastic transformation remain poorly understood. Here, we present a brief review of the genetic and mechanistic aspects of SDH-mutated PPGLs.

Mannelli M, Rapizzi E, Fucci R, et al.
15 YEARS OF PARAGANGLIOMA: Metabolism and pheochromocytoma/paraganglioma.
Endocr Relat Cancer. 2015; 22(4):T83-90 [PubMed] Related Publications
The discovery of SDHD as a pheochromocytoma/paraganglioma susceptibility gene was the prismatic event that led to all of the subsequent work highlighting the key roles played by mitochondria in the pathogenesis of these tumors and other solid cancers. Alterations in the function of tricarboxylic acid cycle enzymes can cause accumulation of intermediate substrates and subsequent changes in cell metabolism, activation of the angiogenic pathway, increased reactive oxygen species production, DNA hypermethylation, and modification of the tumor microenvironment favoring tumor growth and aggressiveness. The elucidation of these tumorigenic mechanisms should lead to novel therapeutic targets for the treatment of the most aggressive forms of pheochromocytoma/paraganglioma.

Zhu WD, Wang ZY, Chai YC, et al.
Germline mutations and genotype-phenotype associations in head and neck paraganglioma patients with negative family history in China.
Eur J Med Genet. 2015; 58(9):433-8 [PubMed] Related Publications
The aim of this study was to assess the frequency of germline mutations and to explore genotype-phenotype associations in Chinese head and neck paraganglioma (HNPGL) patients without family history. Twenty-six Chinese patients with a diagnosis of HNPGL(14 male and 12 female, respectively)were recruited, who were followed up from 2000 to 2012. Genomic DNA was obtained from resected tumor tissues and peripheral blood samples. Seven genes, Succinate dehydrogenase complex A,B,C,D (SDHA, SDHB, SDHC, SDHD), succinate dehydrogenase complex assembly factor 2 (SDHAF2), TMEM127 (transmembrane protein 127) and VHL (Von Hippel-Lindau), were screened by direct sequencing and multiplex ligation-dependent probe amplification (MLPA) was performed to search for potential large deletions or duplications of SDHB, SDHC, SDHD, SDHAF1 and SDHAF2. The total frequency of germline mutations was 30.8% (8/26), including 5 cases with missense mutation p.Met1Ile in SDHD, 1 case with missense mutation p.Tyr216Cys in SDHB, and 1 case with a novel truncation mutation p.Gln44Ter in SDHAF2. MLPA showed one patient with malignant HNPGL had heterozygous deletions of exon1, 2, 3, 7 and 8 in SDHB. Mutations in SDHD were the leading cause of HNPGL in this study. Mutation carriers were younger than non-mutation carriers (p < 0.01) and more likely to suffer from multiple tumors (p = 0.048), especially with mutations in SDHD. The presence of mutation was associated with the development of larger tumors (p = 0.021). This study confirmed that the missense mutation p.Met1Ile at the start codon in SDHD was a hotspot in chinese patients with HNPGLs. We recommend genetic analysis in patients below 45 years, especially SDHD gene.

Bugalho MJ, Silva AL, Domingues R
Coexistence of paraganglioma/pheochromocytoma and papillary thyroid carcinoma: a four-case series analysis.
Fam Cancer. 2015; 14(4):603-7 [PubMed] Related Publications
The paraganglioma (PGL)/pheochromocytoma (PHEO)-papillary thyroid carcinoma (PTC) dyad has been reported rarely. Whether the association is coincidental or results from an underlying genetic predisposition is difficult to ascertain. We analyzed clinical and molecular data on four unrelated patients identified and treated by one of us (MJB) at a tertiary center. Patients were screened for germline variants in a panel of candidate genes: RET, VHL, SDHB, SDHC, SDHD, SDHAF2, TMEM127, MAX, PTEN, CDKN1B. All patients were female; median age at diagnosis of PGL/PHEO was 45 years and at diagnosis of PTC was 49.5 years. Only one patient had family history of thyroid cancer. PTC was multifocal in 2 cases, of the classical type in 2 cases and of the follicular type in 2 cases. Two patients harbored heterozygous germline variants of uncertain significance in the SDHB gene: Ser163Pro and Ala3Gly. The -79T>C polymorphism in the CDKN1B gene was present in all patients (3 in homozygous and 1 in heterozygous state). Results deriving from a comprehensive analysis of a panel of genes suggest that there is no single explanation for the association PGL/PHEO-PTC. It may occur through different mechanisms such as the combinatorial effect of different genetic variants, be a coincidental association or, alternatively, result from genetic variants in genes still awaiting identification.

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