SDHD Mutations Research Articles

7958 Organ Of Zuckerkandl Paragangliomas

Abstract Disclosure: L. McVicker: None. S. Egan: None. K.C. Conlon: None. J. Gibney: None. J. Feeney: None. M. Whelan: None. A. Garrahy: None. Background: The Organ of Zuckerkandl (OoZ) was first described in 1901 by an Austrian anatomist Emile Zuckerkandl as a para-aortic paraganglia located laterally to the abdominal aorta at the level of the inferior mesenteric artery. It represents the largest accumulation of extra-adrenal chromaffin cells in mammals. Paragangliomas (PGL) of the OoZ are rare entities with prior retrospective study of 371 patients with phaeochromocytoma or sympathetic PGL revealing only 21 cases of OoZ PGLs of which 14 of which (66%) had metastases at diagnosis (1). 70% of cases are in association with SDHB or less commonly, SDHD mutations (2). Clinical Case: A 48-year-old female presented with a year long history of palpitations and headache. Plasma normetanephrine level was 6340 pmol/L (lab reference 0-1180), plasma metanephrine 412 pmol/L (lab reference 0-510) and plasma 3-methoxytyramine <100 pmol/L (lab reference 0-180). CT adrenals showed normal adrenal glands. A 4.5 cm x 2.1 cm hyper-vascular retroperitoneal mass was visualised. A 68Ga-DOTATOC PET/CT showed no abnormal uptake in the area of the mass. [1]23I-MIBG scan showed increased uptake within the mass compatible with a PGL of the OoZ. Following surgery, histology confirmed PGL of the OoZ and plasma metanephrines normalised following. Genetic testing for predisposing mutation was negative. A 38-year-old male presented with sweating episodes, palpitations, and hypertension. Plasma normetanephrine level was 2,230 pmol/L (lab reference 0-1180) and plasma metanephrines 223 pmol/L (lab reference 0-520). CT adrenals showed normal adrenal glands with no other abnormalities noted. [1]23I-MIBG showed increased uptake in the region of the origin of the inferior mesenteric artery from the aorta consistent with PGL of the OoZ. The patient underwent laparoscopic resection with resultant normalisation of metanephrine levels. Histology showed a 21 mm encapsulated tumour in keeping with PGL with a PASS Score of 7. As with the first case, genetic testing for predisposing mutations returned negative. Conclusion: OoZ PGLs represent rare presentations of phaeochromocytoma-paraganglioma disease. This small case series is notable as neither case was associated with a predisposing genetic mutation, which has previously been shown to be more common in OoZ PGLs. There was also no evidence of metastasis in either case which is more commonly associated with this OoZ disease. The first case is also remarkable in terms of the tumour’s imaging characteristics. Previous studies have shown greater sensitivity using 68Ga-DOTA-Somatostatin Analogue PET/CT in comparison to [1]23I-MIBG in the detection of PGLs (3). In the first case, the tumour did not show any significant avidity on 68Ga-DOTATOC PET/CT but was avid on [1]23I-MIBG. Reference: 1. Ayala-Ramirez et al. J Clin Endocrinol Metab. 2011 2. Lodish et al. Endocr Relat Cancer. 2010 3. Carrasquillo et al. J Nuclear Medicine. 2021 Presentation: 6/2/2024

12315 Unveiling A Paraganglioma: Catecholamine-Induced Hyperglycemia Masquerading As Type 2 Diabetes Mellitus

Abstract Disclosure: S. Salman: None. M. Hussine: None. J. Tibaldi: None. Background: Excessive catecholamines have been demonstrated to exert adverse effects on insulin homeostasis and carbohydrate metabolism, potentially resulting in the onset of secondary DM. We present a case of a patient who had been previously misdiagnosed with T2DM for an extended period. Clinical Case: A 34-year-old woman with history of T2DM, HTN, and chronic tachycardia on beta blockers, presented with complaints of palpitations, headaches, and abdominal pain for two weeks. Upon admission, she was found to be in DKA, necessitating transient administration of insulin drip. Furthermore, she exhibited persistent tachycardia and intermittent episodes of hypertensive urgency. Notably, thyroid levels revealed euthyroidism. Although DKA resolved, her fasting blood sugar levels remained elevated and refractory to escalating insulin therapy. CT abdomen with contrast revealed a large enhancing mass in the RUQ. MRI abdomen confirmed an 8.1 cm heterogeneously enhancing T2 hyperintense mass located in the RUQ, abutting the right hepatic lobe, right adrenal gland, extrahepatic biliary ducts, and adjacent vessels. Given suspicions of a neuroendocrine tumor, she was transferred to the surgical service for tumor excision. Hormonal analysis revealed elevations in plasma metanephrines (620 pg/mL, n 0-88 pg/mL), plasma normetanephrines (9954 pg/mL, n 0-210.1 pg/mL), 24-hr urine normetanephrines (10,952 μg/24hr, n 110-720 μg/24hr) and 24-hr urine metanephrines (1406 μg/24hr, n 35-278 μg/24hr). Additionally, she exhibited elevated 24-hr urine epinephrine fraction (218 μg/g Cr, 0-20 μg/g Cr) and 24-hr urine norepinephrine fraction (2775 μg/g Cr, 0-45 μg/g Cr). Preoperatively, appropriate alpha and beta blockade were administered, followed by successful retroperitoneal tumor resection. Postoperatively, her glucose levels normalized without the need for further insulin therapy, and no episodes of hypoglycemia were reported. Histopathological examination of the excised mass revealed an 11 cm sympathetic paraganglioma with retention of SDHB staining. Genetic testing for SDHB, SDHD, VHL, and RET mutations is pending. Conclusion: This case underscores the potential oversight of pheochromocytomas and paragangliomas due to their nonspecific symptomatology, often mimicking more prevalent conditions, thereby presenting diagnostic challenges. The catecholamines secreted by these tumors can lead to both impaired insulin secretion and increased insulin resistance, resulting in clinically significant manifestations. The exact mechanism underlying the glycemic dysregulation remains controversial, necessitating further investigation through large-scale multicenter prospective studies to enhance understanding and inform diagnostic and therapeutic strategies for these tumors, which can manifest with severe and potentially fatal glycemic disturbances. Presentation: 6/1/2024

Clinical management and outcome of head and neck paragangliomas (HNPGLs): A single centre retrospective study.

Head and neck paragangliomas (HNPGLs) are rare, usually benign, slow-growing tumours arising from neural crest-derived tissue. Definitive management pathways for HNPGLs have yet to be clearly defined. To review our experience of the clinical features and management of these tumours and to analyse outcomes of different treatment modalities. Demographic and clinical data were obtained from The Northern Ireland Electronic Care Record (NIECR) as well from a prospectively maintained HNPGL database between January 2011 through December 2023. There were 87 patients; 50 females: 37 males with a mean age of 52.3 ± 14.2 years old (range 17-91 years old). 58.6% (n = 51) of patients had carotid body tumours, 25.2% (n = 22) glomus vagal tumours, 6.8% (n = 6) tumours in the middle ear, 2.2% (n = 2) in the parapharyngeal space and 1.1% (n = 1) in the sphenoid sinus. 5.7% (n = 5) of patients had multifocal disease. The mean tumour size at presentation was 3.2 ± 1.4 cm (range 0.5-6.9 cm). Pathogenic SDHD mutations were identified in 41.3% (n = 36), SDHB in 12.6% (n = 11), SDHC in 2.2% (n = 2) and SDHA in 1.1% (n = 1) of the patients. Overall treatment modalities included surgery alone in 51.7% (n = 45) of patients, radiotherapy in 14.9% (n = 13), observation in 28.7% (n = 25), and somatostatin analogue therapy with octreotide in 4.5% (n = 4) of patients. Factors associated with a significantly higher risk of recurrence included age over 60 years (p = .04), tumour size exceeding 2 cm (p = .03), positive SDHx variants (p = .01), and vagal and jugular tumours (p = .04). The majority of our patients underwent initial surgical intervention and achieved disease stability. Our results suggest that carefully selected asymptomatic or medically unfit patients can be safely observed provided lifelong surveillance is maintained. We advocate for the establishment of a UK and Ireland national HNPGL registry, to delineate optimal management strategies for these rare tumours and improve long term outcomes.

Head and Neck Paragangliomas: Overview of Institutional Experience.

Head and neck paragangliomas (HNPGLs) are rare and have high rates of genetic mutations. We conducted a retrospective review of 187 patients with 296 PGLs diagnosed between 1974 and 2023. The mean age of diagnosis was 48.8 years (range 10 to 82) with 69.0% female and 26.5% patients with multiple PGLs. Among 119 patients undergoing genetic testing, 70 (58.8%) patients had mutations, with SDHB (30) and SDHD (26) being the most common. The rates of metastasis and recurrence were higher among patients with SDHB mutations or SDHD mutations associated with multiple PGLs. Metabolic evaluation showed elevated plasma dopamine levels were the most common derangements in HNPGL. MRI and CT were the most common anatomic imaging modalities and DOTATATE was the most common functional scan used in this cohort. Most patients (81.5%) received surgery as the primary definitive treatment, while 22.5% patients received radiation treatment, mostly as an adjuvant therapy or for surgically challenging or inoperable cases. Systemic treatment was rarely used in our cohort. Our single-center experience highlights the need for referral for genetic testing and metabolic evaluation and for a team-based approach to improve the clinical outcomes of patients with HNPGLs.

Succinate dehydrogenase mutations in head and neck paragangliomas: A systematic review and meta-analysis of individual patients' data.

Head and neck paragangliomas (HNPs) have been associated with gene mutations in the succinate dehydrogenase (SDH) complex, but the clinical significance remains unclear. We sought to explore the demographics, clinical characteristics, treatment methods, and outcomes of SDH-mutated HNPs. Databases were systematically searched. Pooled event ratio and relative 95% confidence intervals were calculated for dichotomous outcomes. Meta-regression was performed. Cochran's Q test and I2 test assessed heterogeneity. Funnel plot and Egger's regression test assessed publication bias. Forty-two studies with 8849 patients were included. Meta-regression revealed a significant correlation between multifocality and SDHD mutations (0.03 ± 0.006, p < 0.0001) and between distant metastases and SDHB mutations (0.06 ± 0.023, p = 0.008). There was no correlation between sex, age, tumor size, or familial occurrences and SDH-related mutations. Multifocality of HNPs correlates with the SDHD mutational subtype, and metastases correlate with the SDHB subtype. Knowledge of HNP phenotypes associated with SDH-related mutations has the potential to influence the management approach to such HNPs.

Algorithm of genetic diagnosis for patients with head and neck paraganglioma-update.

Paragangliomas are rare tumors originating from the paraventricular bodies of the autonomic nervous system located in the adrenal glands, chest, abdomen, pelvis and head and neck. Tumors of this type account for 0.5% of head and neck cancers, 0.03% of all cancers and their incidence is estimated at 1-30/100,000 per year. Head and Neck Paragangliomas (HNPGL) are localized in carotid body, tympanic cavity or jugular foramen. It is established that HNPGL may be associated with mutations of the SDH complex, with SDHD being the most prevalent. However, SDHB, SDHC and SDHAF are also potential causes. The aforementioned mutations are influenced by various risk factors, including young age, a positive family history of paraganglioma, the presence of metastases and gender The purpose of this study is to summarize the results of genetic testing performed on patients with head and neck paraganglioma and to create an up-to-date genetic diagnosis algorithm for patients with HNPGL based on previous studies published in the literature that can be used in daily practice. Several papers observed that among SDHD mutation carriers, most or all of those studied had HNPGL, and SDHB mutations were more frequently found in the presence of metastasis. Based on the results, it was concluded that there is no basis for genetic testing for VHL in patients without a positive family history. In each algorithm proposed by different authors, proposals for rational genetic diagnosis were analyzed based on the studies cited by the author and the analyses included in our paper. For the analysis of the treatment algorithms, the following were included: Martin, Mannelli, Neumann, Gupta. Subsequently, publications related to the genetic diagnosis of HNPGL were analyzed to verify the proposed algorithms in light of the latest genetic studies and to establish an updated diagnostic management scheme.

Outcomes of systemic treatment according to germline mutational status in patients with metastatic pheochromocytoma and paraganglioma

IntroductionMetastatic disease affects approximately 15% to 17% of patients with pheochromocytomas and paragangliomas (PPGLs). Unfortunately, treatment options for metastatic PPGLs are limited and rely on small, nonrandomized clinical trials. The impact of germline mutation status on systemic treatment outcomes remains unclear. To address these gaps, we retrospectively evaluated treatment outcomes in patients with PPGL. Patients and MethodsBetween December 2004 and December 2021, 33 patients were diagnosed with metastatic PPGLs and received systemic treatment at the Department of Oncology, Asan Medical Center, Seoul, South Korea. ResultsThe median age of the patients was 49. Germline mutations were revealed in nine patients (39.1%) out of 23 who underwent germline testing, with SDHB mutation being the most frequent in 5 patients. Cyclophosphamide, vincristine, and dacarbazine (CVD) chemotherapy was administered to 18 patients, with an objective response rate (ORR) of 22% and a disease control rate (DCR) of 67%. The median progression-free survival (PFS) was 7.9 and the median overall survival (OS) was 36.2 months. Sunitinib was given to 6 patients, which had an ORR of 33%, a DCR of 83%, and a median PFS of 14.6 months. Notably, patients with SDHB/SDHD mutation (4 patients and one patient, respectively) who received CVD treatment had a significantly better OS than those without (median OS 94.0 months vs. 13.7 months, P = .01). ConclusionOur study reveals that CVD and sunitinib are effective treatments for metastatic PPGLs. The results are consistent with previous studies and patients with SDHB and SDHD mutations may benefit most from CVD treatment.

Molecular features of gastrointestinal stromal tumors “wild-type” (&lt;i&gt;KIT/PDGFRA&lt;/i&gt; WT)

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Their main features are the expression of CD117 (KIT) and mutations of KIT or PDGFRA in 85 % of patients. however, 10–15 % of adult GIST and 85 % of pediatric GIST do not have KIT/PDGFRA mutations (KIT/PDGFRA WT GIST or “wild-type” GIST). The prognosis and clinical course of these tumors and GIST with KIT/PDGFRA mutations differ. “Wild-type” GIST are quite heterogeneous group of tumors in terms of clinical phenotype, genetic etiology, and molecular pathways. Gastrointestinal stromal tumors are divided into SDH-deficient and SDH-competent based on the succinate dehydrogenase (SDH) complex. SDH-deficient GIST occur predominantly in children and young patients with Carney–Stratakis syndrome and Carney triad; there are also sporadic tumors. More than half of SDH-deficient GIST contain mutations in SDHA, SDHB, SDHD or SDHC, while the rest are caused by hypermethylation of the SDHC promoter. SDH-competent “wild-type” GIST include tumors with BRAF, RAS, or NF1 mutations that activate the RAS-RAF-MAPK pathway and KIT/PDGFRA/SDH/RAS-P WT GIST subtype or “quadruple wild type” GIST. The genomic profiles of these tumors and GIST with KIT/PDGFRA mutation or SDH deficiency differ significantly. One of the features of “quadruple wild type” GIST is activation of the FGFR (fibroblast growth factor receptors) signaling pathway due to chimeric FGFR, FGFR mutations, or overexpression of FGF (fibroblast growth factor). Another feature is chimeric genes containing fragments of NTRK, BRAF, FGFR and other genes that behave as oncogene drivers. In “quadruple wild-type” GIST the somatic mutations in TP53, MAX, MEN1, CTNND2, CHD4, ARIDIA and other genes were revealed as well as in the cell cycle genes RB1, CDK4, CDKN1B. There is no specific treatment for patients with “wild-type” GIST; the choice of drug is determined by the genetic disorder. There is a need to improve our understanding of the molecular mechanisms underlying the different GIST subtypes to develop more effective therapeutic approaches.

Five-Fraction Stereotactic Radiation for Head and Neck Paragangliomas

Paragangliomas of the head and neck (HN) are benign, slow-growing neoplasms that are rarely functional. Treatment is often indicated for patients presenting with mass effect, cranial neuropathies, or pulsatile tinnitus. Radiotherapy, traditionally conventionally fractionated, is often used for primary, post-operative, and salvage therapy, given its excellent control rates and reduced risks to adjacent neurovascular structures. Stereotactic ablative radiation (SAbR) offers shorter treatment time, and modern techniques eliminate margins to improve organ-at-risk avoidance. SAbR may offer additional radiobiological sparing of normal structures over single-fraction SAbR. We aimed to evaluate tumor and symptom response, acute and late toxicity rates, and recurrence patterns in HN paraganglioma patients treated with 25 Gy in 5 fractions. Retrospective chart review collected baseline patient and tumor information, treatment and dosimetry details, acute and long-term toxicity grades (per the CTCAE v. 5.0), symptom and tumor response, and survival. Local control was defined as the absence of local enlargement (per RECIST v. 1.1) or marginal failure and was estimated using the Kaplan-Meier method. Between December 2009-March 2020, 39 patients received 25 Gy in 5 fractions to 43 HN paragangliomas, of which 17 were treated in 11 patients with hereditary paraganglioma-pheochromocytoma syndrome. Fifteen targets were post-operative recurrent or residual tumors. There were 27 jugulotympanic tumors, 4 jugular, 1 tympanic, 8 vagal, 5 carotid body, and 2 jugulotympanic or vagal. Median follow-up time was 3.3 years (range 0-11.4 years), and 21 targets had at least 4 years of follow-up. Tumor volume decreased by a median of 37%. Three-year local control was 100%. One patient, known to harbor an SDHD mutation, had 2 out-of-field recurrences within the post-operative bed at 7.1 years. Two patients experienced 2 marginal recurrences within the post-operative bed at 6.1 and 8.4 years: one had an SDHB mutation and developed metastatic disease, and the other did not have genetic testing. The most common grade 1-2 acute toxicities were headache and fatigue; the most common grade 1-2 late toxicities were dysphagia and otalgia. There were no grade >2 acute toxicities. A late grade 3 aspiration event was seen in 1 patient who presented with paralyzed vocal cord requiring multiple medialization laryngoplasties. Within 6 months of SAbR, 18% of symptoms or toxicities improved or resolved; 34% improved or resolved more than 6 months after SAbR. This is the largest series of HN paragangliomas treated with SAbR, detailing a 10-year experience with a 5-fraction regimen that is well-tolerated and achieves excellent local control. Post-SAbR recurrences occurred outside of the radiation field but within the post-operative bed, suggesting that some post-operative patients may benefit from expanded radiation volumes or close surveillance for salvage therapy.

Morphological, immunohistochemical, and genetic analyses of epithelioid gastrointestinal stromal tumors

Epithelioid gastrointestinal stromal tumors (GISTs) are rare and may be confused with other tumors with epithelioid morphology. Therefore, herein, we collected 12 epithelioid GIST samples and summarized their morphological and immunohistochemical characteristics. Through genetic testing, we explored the correlation between morphology and gene mutations. The results showed that eight tumors showed focal or diffuse myxoid stromal changes with less cohesively arranged rhabdoid tumor cells; among these, five showed platelet-derived growth factor receptor alpha gene (PDGFRA) mutations. Signet ring cells with sclerosing stroma and receptor tyrosine kinase type III gene (KIT) mutations were present in two cases, which might be a KIT mutation-associated growth pattern in epithelioid GISTs. Succinate dehydrogenase gene (SDH) mutations were detected in three cases. Simultaneously, PDGFRA mutations were detected in two cases, and the Kirsten rat sarcoma viral oncogene homolog gene (KRAS) mutation was detected in another case. SDH-subunit B (SDHB) expression was partially weak and strongly diffuse in two cases with concurrent PDGFRA and SDHD mutations, respectively. The coexistence of PDGFRA and SDHD mutations may have affected SDHB expression. Altogether, we concluded that PDGFRA mutations may play an important role in co-mutant GIST pathogenesis.

SDHA Germline Mutations in SDH-Deficient GISTs: A Current Update.

Loss of function of the succinate dehydrogenase complex characterizes 20-40% of all KIT/PDGFRA-negative GIST. Approximately half of SDH-deficient GIST patients lack SDHx mutations and are caused by a hypermethylation of the SDHC promoter, which causes the repression of SDHC transcription and depletion of SDHC protein levels through a mechanism described as epimutation. The remaining 50% of SDH-deficient GISTs have mutations in one of the SDH subunits and SDHA mutations are the most common (30%), with consequent loss of SDHA and SDHB protein expression immunohistochemically. SDHB, SDHC, and SDHD mutations in GIST occur in only 20-30% of cases and most of these SDH mutations are germline. More recently, germline mutations in SDHA have also been described in several patients with loss of function of the SDH complex. SDHA-mutant patients usually carry two mutational events at the SDHA locus, either the loss of the wild type allele or a second somatic event in compound heterozygosis. This review provides an overview of all data in the literature regarding SDHA-mutated GIST, especially focusing on the prevalence of germline mutations in SDH-deficient GIST populations who harbor SDHA somatic mutations, and offers a view towards understanding the importance of genetic counselling for SDHA-variant carriers and relatives.

The SDHD:p.H102R Variant Is Frequent in Russian Patients with Head and Neck Paragangliomas and Associated with Loss of 11p15.5 Region and Hypermethylation of H19-DMR

Head and neck paragangliomas (HNPGLs) are rare neuroendocrine neoplasms derived from the parasympathetic paraganglia of the head and neck. At least 30% of HNPGLs are linked to germline mutations, predominantly in SDHx genes. In this study, we analyzed an extended cohort of Russian patients with HNPGLs using whole-exome sequencing and found a highly frequent missense variant p.H102R in the SDHD gene. We determined this variant in 34% of the SDHD mutation carriers. This variant was associated with somatic loss of the gene wild-type allele. Data from the B allele frequency method and microsatellite and microdeletion analysis indicated evident LOH at the 11p15.5 region and potential loss of the whole of chromosome 11. We found hypermethylation of H19-DMR in all tumors, whereas differential methylation of KvDMR was mostly retained. These findings do not support the paternal transmission of SDHD:p.H102R but are in agreement with the Hensen model. Using targeted sequencing, we also studied the variant frequency in a control cohort; we found SDHD:p.H102R in 1.9% of cases, allowing us to classify this variant as pathogenic. The immunohistochemistry of SDHB showed that the SDHD:p.H102R mutation, even in combination with wild-type allele loss, does not always lead to SDH deficiency. The obtained results demonstrate the frequent variant associated with HNPGLs in a Russian population and support its pathogenicity. Our findings help with understanding the mechanism of tumorigenesis and are also important for the development of cost-effective genetic screening programs.

Succinate dehydrogenase inversely regulates red cell distribution width and healthy life span in chronically hypoxic mice.

Increased red cell distribution width (RDW), which measures erythrocyte mean corpuscular volume (MCV) variability (anisocytosis), has been linked to early mortality in many diseases and in older adults through unknown mechanisms. Hypoxic stress has been proposed as a potential mechanism. However, experimental models to investigate the link between increased RDW and reduced survival are lacking. Here, we show that lifelong hypobaric hypoxia (~10% O2) increased erythrocyte numbers, hemoglobin, and RDW, while reducing longevity in male mice. Compound heterozygous knockout (hKO) mutations in succinate dehydrogenase (Sdh; mitochondrial complex II) genes Sdhb, Sdhc, and Sdhd reduced Sdh subunit protein levels, reduced RDW, and increased healthy life span compared with WT mice in chronic hypoxia. RDW-SD, a direct measure of MCV variability, and the SD of MCV showed the most statistically significant reductions in Sdh hKO mice. Tissue metabolomic profiling of 147 common metabolites showed the largest increase in succinate with elevated succinate/fumarate and succinate/oxoglutarate (2-ketoglutarate) ratios in Sdh hKO mice. These results demonstrate that mitochondrial complex II level is an underlying determinant of both RDW and healthy life span in hypoxia and suggest that therapeutic targeting of Sdh might reduce high RDW–associated clinical mortality in hypoxic diseases.

Succinate dehydrogenase and MYC-associated factor X mutations in pituitary neuroendocrine tumours.

Pituitary neuroendocrine tumours (PitNETs) associated with paragangliomas or phaeochromocytomas are rare. SDHx variants are estimated to be associated with 0.3–1.8% of PitNETs. Only a few case reports have documented the association with MAX variants. Prolactinomas are the most common PitNETs occurring in patients with SDHx variants, followed by somatotrophinomas, clinically non-functioning tumours and corticotrophinomas. One pituitary carcinoma has been described. SDHC, SDHB and SDHA mutations are inherited in an autosomal dominant fashion and tumorigenesis seems to adhere to Knudson’s two-hit hypothesis. SDHD and SDHAF2 mutations most commonly have paternal inheritance. Immunohistochemistry for SDHB or MAX and loss of heterozygosity analysis can support the assessment of pathogenicity of the variants. Metabolomics is promising in the diagnosis of SDHx-related disease. Future research should aim to further clarify the role of SDHx and MAX variants or other genes in the molecular pathogenesis of PitNETs, including pseudohypoxic and kinase signalling pathways along with elucidating epigenetic mechanisms to predict tumour behaviour.

A Four-Generational Report on Hereditary Head and Neck Paraganglioma.

BackgroundThis article investigates the inheritance, penetrance, clinical presentation, and therapeutic outcomes of hereditary head and neck paragangliomas (HNPGLs) by offering a four-generational report of an 18-member family affected by this rare condition.MethodologyInformation was compiled by examination of patients and a review of medical records and correspondence (retrospective case series).ResultsSix members of the 18-member family were diagnosed with HNPGL between 2002 and 2018. A known pathogenic point mutation in subunit D of the succinyl dehydrogenase complex (SDHD, c.317G>T, p.Gly106Val) was responsible for the tumor phenotype. The mutation could be revealed in seven family members, three diseased adults, one healthy adult, and three healthy children, out of the nine who consented to gene testing. The median age at diagnosis was 33.5 years (range: 22-50 years). Five of the eight primary tumors were glomus caroticum, two were glomus jugulare, and one was a glomus vagale tumor. The therapeutic approaches were multimodal and included embolization therapy, surgery, radiation, and watchful waiting. Follow-up was reported for five of the six patients (mean follow-up of 34.8 months after primary therapy); three showed no disease progression or recurrence.ConclusionsThis study exemplifies the autosomal dominant, parent-of-origin-dependent inheritance and the high disease penetrance in hereditary paraganglioma-pheochromocytoma syndromes. Six out of a total of eight adult descendants (75%) of the original SDHD mutation carrier developed tumors, and the morbidity associated with the disease as well as its therapy was especially high in late-diagnosed, advanced cases. This substantiates the necessity for early radiologic surveillance and genetic testing.

SDHB knockout and succinate accumulation are insufficient for tumorigenesis but dual SDHB/NF1 loss yields SDHx-like pheochromocytomas.

SUMMARYInherited pathogenic succinate dehydrogenase (SDHx) gene mutations cause the hereditary pheochromocytoma and paraganglioma tumor syndrome. Syndromic tumors exhibit elevated succinate, an oncometabolite that is proposed to drive tumorigenesis via DNA and histone hypermethylation, mitochondrial expansion, and pseudohypoxia-related gene expression. To interrogate this prevailing model, we disrupt mouse adrenal medulla SDHB expression, which recapitulates several key molecular features of human SDHx tumors, including succinate accumulation but not 5hmC loss, HIF accumulation, or tumorigenesis. By contrast, concomitant SDHB and the neurofibromin 1 tumor suppressor disruption yields SDHx-like pheochromocytomas. Unexpectedly, in vivo depletion of the 2-oxoglutarate (2-OG) dioxygenase cofactor ascorbate reduces SDHB-deficient cell survival, indicating that SDHx loss may be better tolerated by tissues with high antioxidant capacity. Contrary to the prevailing oncometabolite model, succinate accumulation and 2-OG-dependent dioxygenase inhibition are insufficient for mouse pheochromocytoma tumorigenesis, which requires additional growth-regulatory pathway activation.

Genetics of Head and Neck Paragangliomas

Paragangliomas of the head and neck (HNPGL) are rare neurogenic tumors, in which genetic factors play a certain role. So far, 10 genes related to HNPGL (SDHA、SDHB、SDHC、SDHD、SDHAF2、VHL、HIF2A、RET、NF1 and TMEM127) have been found. The clinical phenotypes of different gene mutations are different. SDHD、SDHC and SDHAF2 gene mutations are almost 100% related to HNPGL. SDHD and SDHAF2 gene mutations tend to form multiple paragangliomas, and its genetic pattern has obviously maternal imprinting. SDHB mutations have sympathetic paraganglioma and malignant tendency. Understanding the molecular mechanism and genotype-phenotypic relationship of paraganglioma can provide significant help for genetic counseling, diagnosis and treatment and follow-up strategies in patients with HNPGL.

Head and Neck Malignant Paragangliomas: Experience from a Single Institution.

Objectives: To summarize the clinicopathological and genetic features of malignant paragangliomas in head and neck cancer and to explore the appropriate treatment options for this rare lesion. Methods: Six patients harboring head and neck malignant paraganglioma from Beijing Tongren Hospital were retrospectively reviewed. The clinicopathological characteristics, gene mutations, and prognosis of these patients were analyzed. Results: Of these 6 patients, 3 were male and 3 were female; 4 patients harbored malignant carotid body tumors, and two had malignant vagal paragangliomas. Three patients had cervical lymph node metastasis, two presented with lung and bone metastasis, and 1 had lung and liver metastasis. Of the 6 patients, four underwent surgical resection, and the other two patients denied surgery and instead received chemotherapy with paclitaxel, ifosfamide, and dacarbazine. These 2 patients with vagal paraganglioma received postoperative radiotherapy. All 6 patients are still alive at the present time, with a median follow-up time of 66months. Positive Ki-67 expression in tumor tissue ranged from 1% to 40%. Genetic mutations in SDHD, SDHB, ATR, and MAP3K13 were identified in 4 patients. Conclusions: After comprehensive treatment, head and neck malignant paraganglioma can attain a favorable prognosis. Genetic mutations are commonly detected in patients with malignant paragangliomas. This study also identified mutations in ATR and MAP3K13 in these patients.

A FAMILY WITH HEREDITARY PARAGANGLIOMA SECONDARY TO SDHD MUTATION

INTRODUCTIONA third of pheochromocytoma and paraganglioma (PPGL) tumours are part of a hereditary syndrome. Hereditary PPGL shows autosomal dominant inheritance with variable penetrance. Genetic testing is recommended in all patients diagnosed with PPGL regardless of age at presentation and family history. SDHD is the most frequently mutated gene in head and neck PGLs and associated tumours have low malignancy rate. This gene is maternally imprinted with silencing of the maternal allele, thus, the risk of developing paragangliomas is limited to offsprings who inherit the pathogenic variant from their father. Paternally inherited pathogenic variants are highly penetrant by age 50. We describe a family with hereditary paraganglioma due to mutation in the SDHD gene. RESULTSThe index patient is a 23 year-old female who was diagnosed to have bilateral adrenal pheochromocytoma with carotid and cardiac paragangliomas. Genetic screening revealed that she has SDHD mutation. Further family history revealed that 2 out of 3 paternal aunts have carotid paragangliomas. Her father, youngest of 5 siblings, paternal uncle and grandfather passed away at age 42, 40, 39 years old, respectively, due to severe headache and possible haemorrhagic stroke. Six other family members underwent genetic screening as well. Five family members were positive for SDHD mutation. These include the index patient’s elder sister, 3 paternal aunts (2 with carotid paragangliomas) and one male cousin. CONCLUSIONGenetic testing for family members of patients with hereditary paragangliomas is recommended after thorough genetic counselling. Genetic testing for firstand second-degree relatives is recommended for SDHDrelated paraganglioma. Healthy asymptomatic carriers for the gene mutation should undergo clinical assessment, plasma and/or urine metanephrines and normetanephrines and a combination of whole-body MRI (head and neck, abdominal and pelvic) and PET-CT imaging at initial screening. Thereafter, recommendations for long-term surveillance include annual clinical and biochemical evaluation along with whole body MRI repeated every 2-3 years.

Efficacy of Immunohistochemistry for SDHB in the Screening of Hereditary Pheochromocytoma-Paraganglioma.

Simple SummaryThe majority of hereditary pheochromocytoma and paraganglioma (PPGL) is caused by germline mutations in the SDHB, SDHC, or SDHD genes, which encode three (SDHB, SDHC, SDHD) of five subunits of succinate dehydrogenase (SDH) enzyme (SDHA, SDHDB, SDHC, SDHD, SDHAF2). The inactivation of any of the SDHx genes leads to the proteolysis of SDH. This can be detected with negative immunohistochemistry (IHC) for SDHB. However, there is no consensus of the interpretation of “weakly positive” staining. Hence, we carried out a retrospective single centre study comprising 58 patients to evaluate the efficacy of using SDHB IHC for detecting SDHx mutation in PPGL cases. Our analyses revealed that SDHB-negative IHC is a cost-effective and reliable method to predict SDHx mutations in the Korean population. Nonetheless, in the case of weakly positive staining, an additional gene study should be considered.The most common genetic backgrounds of hereditary paraganglioma and pheochromocytoma (PPGL) are SDHx germline mutations. Given the fact that the immunohistochemistry (IHC) result for SDHB is always negative regardless of the type of SDHx mutation, we aimed to evaluate the efficacy of using SDHB IHC for screening SDHx mutations in PPGL cases. In total, 52 patients who underwent surgery for PPGL treatment between 2006 and 2020 and underwent genetic analysis at diagnosis were included. Tissue microarrays (TMAs) were constructed with PPGL tissues and IHC for SDHB was performed on TMA sections. All 10 patients with SDHB-negative IHC contained SDHB or SDHD mutations. The genetic test results of patients with SDHB-weakly positive IHC varied (one SDHB, two RET, one VHL, and three unknown gene mutations). There were no SDHx mutations in the SDHB-positive IHC group. Six patients with weakly positive SDHB IHC with primarily unknown genetic status were re-called and underwent next-generation sequencing. None of them had SDHx mutations. In conclusion, SDHB-negative IHC is a cost-effective and reliable method to predict SDHx mutations. However, in the case of weakly positive SDHB staining, an additional gene study should be considered.