Succinate Dehydrogenase Subunit B Mutations Research Articles

Responses to systemic therapy in metastatic pheochromocytoma/paraganglioma: a retrospective multicenter cohort study.

The therapeutic options for metastatic pheochromocytomas/paragangliomas (mPPGLs) include chemotherapy with cyclophosphamide/vincristine/dacarbazine (CVD), temozolomide monotherapy, radionuclide therapies, and tyrosine kinase inhibitors such as sunitinib. The objective of this multicenter retrospective study was to evaluate and compare the responses of mPPGLs including those with pathogenic variants in succinate dehydrogenase subunit B (SDHB), to different systemic treatments. This is a retrospective analysis of treatment responses of mPPGL patients (n = 74) to systemic therapies. Patients with mPPGLs treated at 6 specialized national centers were selected based on participation in the ENSAT registry. Survival until detected progression (SDP) and disease-control rates (DCRs) at 3 months were evaluated based on imaging reports. For the group of patients with progressive disease at baseline (83.8% of 74 patients), the DCR with first-line CVD chemotherapy was 75.0% (n = 4, SDP 11 months; SDHB [n = 1]: DCR 100%, SDP 30 months), with somatostatin peptide receptor-based radionuclide therapy (PPRT) 85.7% (n = 21, SDP 17 months; SDHB [n = 10]: DCR 100%, SDP 14 months), with 131I-meta-iodobenzylguanidine (131I-MIBG) 82.6% (n = 23, SDP 43 months; SDHB [n = 4]: DCR 100%, SDP 24 months), with sunitinib 100% (n = 7, SDP 18 months; SDHB [n = 3]: DCR 100%, SDP 18 months), and with somatostatin analogs 100% (n = 4, SDP not reached). The DCR with temozolomide as second-line therapy was 60.0% (n = 5, SDP 10 months; SDHB [n = 4]: DCR 75%, SDP 10 months). We demonstrate in a real-life clinical setting that all current therapies show reasonable efficacy in preventing disease progression, and this is equally true for patients with germline SDHB mutations.

Abdominal nonfunctional paraganglioma in which succinate dehydrogenase subunit B (SDHB) immunostaining was performed: a case report

BackgroundAbdominal nonfunctional paraganglioma is rare. Malignant potential of paraganglioma is assessed by Grading of Adrenal Pheochromocytoma and Paraganglioma score and genetic testing, but genetic testing is not common. We present a case of abdominal nonfunctional paraganglioma whose malignant potential was assessed by grading of adrenal pheochromocytoma and paraganglioma score and succinate dehydrogenase subunit B staining alternative to genetic testing.Case presentationA 39-year-old Japanese man had a right retroperitoneal tumor without symptoms. Uptake in the tumor was shown by 123I-meta-iodobenzylguanidine scintigraphy. There were no metastases. The results of biochemical workups including blood hormones and urinary metanephrines were normal. We performed retroperitoneoscopic surgery. The tumor was positive for chromogranin A staining but negative for tyrosine hydroxylase. On the basis of the preoperative biochemical workups and pathology results, we diagnosed the tumor as nonfunctional paraganglioma. The Grading of Adrenal Pheochromocytoma and Paraganglioma score classified the tumor as moderately differentiated. Furthermore, negative succinate dehydrogenase subunit B staining suggested the patient has the SDHx (SDHA, SDHB, SDHC and SDHD) mutation.ConclusionAbdominal nonfunctional PGLs are associated with SDHB mutation, and SDHB staining should be performed as a screening.

PSUN27 Largest Cohort of Cervical Spine Metastases of Pheochromocytoma/Paraganglioma in the Setting of SDHB Mutation

Abstract Background Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors arising from chromaffin cells in adrenal or extra-adrenal locations, respectively. Overall, 10 to 20% of PPGLs are metastatic, with higher metastatic potential observed in succinate dehydrogenase subunit B (SDHB)-related tumors (up to 90%). Metastatic PPGLs are diagnosed based on the presence of tumor cells of chromaffin origin in a location outside the site of normal development (adrenal medulla and the sympathetic chain) in the bones and lymphatic nodes per 2017 WHO guidelines. Studies evaluating both metastatic pheochromocytomas and extra-adrenal PGLs have reported bone to be the most common site of metastasis. Clinical Case We reviewed the metastatic patients in our PPGL cohort and found 40 (29.85%) out of 134 patients with SDHB-related metastatic PPGLs developing metastatic lesions in the cervical spine. The related descriptive analyses were as follows: 25 (62.5%) were males, 15 (37.5%) females. Fourteen patients (35%) have died due to metastatic PPGL complications. The average age of patients at the time of the primary tumor diagnosis was 30.3 ± 35 years and the age at the initial metastatic tumor diagnosis was 34 ± 33 years. The average time interval to metastatic disease was 7.4 ± 38 years. At their initial presentation, there were 25 (62.5%) patients with solitary tumors; 1 (2.5%) with multiple primary tumors; and 14 (35%) with metastatic tumors. All the patients either developed or had metastatic lesions in the cervical vertebrae. Nine (22.5%) patients required surgical fusions of the vertebrae to manage their pathological fractures and another 9 (22.5%) patients received radiation therapy. Conclusion Genetic testing is recommended for all patients with PPGLs. Genetic analysis, especially finding a SDHB mutation may be helpful in determining metastatic potential. Most patients with spinal metastatic lesions are asymptomatic, but when clinical symptoms arise, the most common clinical symptom involves pain and neurological deficit. Metastasis to the spine is an important complication that can lead to significant pain and disability and requires surgical interventions or radiotherapy. Awareness for such spinal tumors is essential for offering the correct treatment to the patients. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

EP-630 Pheochromocytoma Associated with SDHB Mutation: A case report

Abstract Introduction Pheochromocytomas and paragangliomas are rare neuroendocrine tumors arising from the chromaffin cells of the adrenal medulla or extra-adrenal tissues. 10% to 20% of tumors are detected before age 18 years. Approximately 10%–15% of pheochromocytoma and 20%–50% of paraganglioma are malignant. Up to 24% of the cases are familial where they may be associated with genetic syndromes like MEN 2, succinate dehydrogenase subunit B (SDHB) gene mutations and VHL syndrome. Germline mutations in SDHB gene increase the risk of PGLs/ PHEOs and RCC with 38%-83% risk of malignancy. We represent a rare case of pheochromocytoma associated with SDHB mutation in a child. Case presentation A 17-year old patient presented with repeated vomiting and hypertension. BMI was 14.4 kg/m2, BP was 140/112 mmgh, PR was127 peats/min. The rest of the clinical examination was unremarkable. Plasma and 24-hour urinary metanephrines levels were highly elevated together with Chromogranin A level. Abdominal CT and MRI scans revealed an enlarged right adrenal gland measuring approximately 45 mm, indenting but not invading the posterior aspect of the IVC. Management Treatment was initiated with α-blockers; (Doxazosin then phenoxybenzamine); followed by β-blockers. The patient underwent laparoscopic right adrenalectomy. The tumor was 50×30×30 mm and weighting 58g. The tumor was positive with chromogranin, and S100. The PASS score was 2. Genetic mutation was detected at SDGB (c.72+1G>A). Conclusion We recommend genetic testing for all suspecting cases of PHEO/PGLs to establish the appropriate follow-up plan.

Pheochromocytoma Associated With SDHB Mutation: A rare Clinical Presentation

Introduction: Pheochromocytomas and paragangliomas are rare neuroendocrine tumors arising from the chromaffin cells of the adrenal medulla or extra-adrenal para-ganglionic tissues. 10% to 20% of tumors are detected before the age of 18 years. Approximately 20%–50% of these tumors are malignant. Up to 24% of the cases may be associated with genetic syndromes like MEN 2, succinate dehydrogenase subunit B (SDHB) gene mutations and VHL syndrome. SDHB is one of the four subunits of the SDH complex. Germline mutations in SDHB gene increase the risk of PGLs/PHEOs and RCC with 38%-83% risk of malignancy.

Transaminitis Evaluation Leads to the Incidental Diagnosis of Familial Paraganglioma Due to SDHB Mutation

Background: Paragangliomas are rare neuroendocrine tumors. Patients with succinate dehydrogenase subunit B (SDHB) gene mutations are predisposed to developing paraganglioma/pheochromocytoma. We are presenting the case of an incidental finding of a paraganglioma during an evaluation for transaminitis. Clinical Case: A 23-year-old male with a medical history of right hydrocele repair as a teenager was evaluated with an ultrasound of the abdomen for elevated liver enzymes and right upper quadrant discomfort. The ultrasound revealed a large lobular solid vascular 13.8 x 8.1 x 11.3 cm mass in the mid abdomen. He underwent a CT of the chest, abdomen and pelvis which demonstrated a large retroperitoneal mass measuring 16 x 10 x 13.7 cm within the right mid abdomen. The mass was described as a large centrally necrotic peripherally enhancing right retroperitoneal mass displacing the IVC anteriorly. The patient subsequently underwent an image-guided biopsy of the mass and the pathology revealed it was a paraganglioma. The patient denied any history of hypertension, orthostasis, headaches or palpitations. Biochemical workup for plasma catecholamines, plasma metanephrines, 24-hour urine catecholamines and metanephrines and cortisol were unremarkable. His transaminitis also resolved. He underwent a retroperitoneal paraganglioma excision and the final pathology was consistent with paraganglioma and negative for capsular invasion. He was referred to a genetic counsellor for testing since paragangliomas can be inherited. He also mentioned a family history of breast cancer in his mother and HTN and prostate cancer in his father. His test revealed that he had a c.289A>T mutation in his SDHB gene. He was encouraged to share the information with his family to help them understand the implications of his genetic test result. He underwent a surveillance PET scan which showed multiple osseous lesions in his temporal calvarium, sphenoid, spine and sacrum suggestive of metastasis. Repeat imaging with a DOTATATE PET scan showed stable disease. His transaminitis was transient, and we did not find a correlation to his paraganglioma. His imaging tests showed no liver metastasis. A CT of the head showed no evidence of intracranial metastasis. The current plan is to continue surveillance. His older brother underwent a genetic testing. He tested positive for the same SDHB mutation and underwent biochemical and imaging tests which were unremarkable. He too will continue surveillance. Conclusions: Patients with a succinate dehydrogenase subunit B (SDHB) gene mutations are predisposed to developing paraganglioma/pheochromocytoma. The tumors produce catecholamines, but can be biochemically silent as in our patient. They are inherited in an autosomal dominant manner. Our case highlights the importance for genetic counseling which increases the chances of early screening and surveillance in affected family members for optimal multidisciplinary management of patients.

Abstract 12938: An Unusual Case of Malignant Hypertension and Stress Cardiomyopathy Originating From the Urinary Bladder

A 39-year-old man with hypertension presented for an elective knee surgery. Within 15 minutes of induction of anesthesia, he developed malignant hypertension and acute hypoxia. Surgery wasaborted and he was subsequently transferred to our facility. High-sensitivity troponin was elevated. Chest X-ray demonstrated bilateral hilar opacities, consistent with pulmonary edema.Transthoracic echocardiography demonstrated mildly depressed left ventricular function with hypokinesis of the septum and inferolateral wall. Cardiac catheterization showed normal filling pressures and no coronary artery disease. Initial work up for secondary hypertension, including Duplex Doppler ultrasonography of renal artery and serum aldosterone level were unrevealing. Because of high index of suspicion, additional workup was pursued for adrenal hypertension. Hewas found to have severely elevated plasma normetanephrine level (36 nmol/L) and 24-hrurinary normetanephrine of 8,990 mcg while plasma metanephrine and epinephrine levels were within normal limits. Computed tomography of abdomen showed no adrenal mass but revealed contrast-enhancing mass in the bladder wall with surrounding lymphadenopathy, suggestive of metastatic paraganglioma. He underwent genetic evaluation which identified a heterozy gouspathogenic variant in the succinate dehydrogenase subunit B (SDHB) gene. He was treated withalpha- and beta-blockade and underwent partial cystectomy with lymph node dissection. Follow-up Gallium-68 DOTATATE scan was positive for uptake in several lymph nodes withsubsequent successful lymph node dissection. He is now asymptomatic. Discussion: This case illustrates the importance of a complete history in the evaluation of hypertension inyoung people. The presence of labile hypertension and acute cardiomyopathy which isprecipitated by stress or noncardiac surgery should prompt an evaluation of pheochromocytoma.The isolated elevation in plasma and urinary normetanephrine with normal plasma/urinarymetanephrine level is consistent with extra-adrenal production of catecholamines, which iscommon in the presence of SDHB mutation.

Targeting pheochromocytoma/paraganglioma with polyamine inhibitors

BackgroundPheochromocytomas (PCCs) and paragangliomas (PGLs) are neuroendocrine tumors that are mostly benign. Metastatic disease does occur in about 10% of cases of PCC and up to 25% of PGL, and for these patients no effective therapies are available. Patients with mutations in the succinate dehydrogenase subunit B (SDHB) gene tend to have metastatic disease. We hypothesized that a down-regulation in the active succinate dehydrogenase B subunit should result in notable changes in cellular metabolic profile and could present a vulnerability point for successful pharmacological targeting. MethodsMetabolomic analysis was performed on human hPheo1 cells and shRNA SDHB knockdown hPheo1 (hPheo1 SDHB KD) cells. Additional analysis of 115 human fresh frozen samples was conducted. In vitro studies using N1,N11-diethylnorspermine (DENSPM) and N1,N12- diethylspermine (DESPM) treatments were carried out. DENSPM efficacy was assessed in human cell line derived mouse xenografts. ResultsComponents of the polyamine pathway were elevated in hPheo1 SDHB KD cells compared to wild-type cells. A similar observation was noted in SDHx PCC/PGLs tissues compared to their non-mutated counterparts. Specifically, spermidine, and spermine were significantly elevated in SDHx-mutated PCC/PGLs, with a similar trend in hPheo1 SDHB KD cells. Polyamine pathway inhibitors DENSPM and DESPM effectively inhibited growth of hPheo1 cells in vitro as well in mouse xenografts. ConclusionsThis study demonstrates overactive polyamine pathway in PCC/PGL with SDHB mutations. Treatment with polyamine pathway inhibitors significantly inhibited hPheo1 cell growth and led to growth suppression in xenograft mice treated with DENSPM. These studies strongly implicate the polyamine pathway in PCC/PGL pathophysiology and provide new foundation for exploring the role for polyamine analogue inhibitors in treating metastatic PCC/PGL. PrécisCell line metabolomics on hPheo1 cells and PCC/PGL tumor tissue indicate that the polyamine pathway is activated. Polyamine inhibitors in vitro and in vivo demonstrate that polyamine inhibitors are promising for malignant PCC/PGL treatment. However, further research is warranted.

MON-199 Targeting Pheochromocytoma/Paraganglioma with Polyamine Inhibitors

Background: Pheochromocytomas (PCCs) and paragangliomas (PGLs) are neuroendocrine tumors that are mostly benign. Metastatic disease occurs in about 10% of cases, and for these patients no effective therapies are available. Patients with mutations in the succinate dehydrogenase subunit B (SDHB) gene tend to have metastatic disease with very little treatment options. To find a new treatment strategy, we utilized a metabolomics approach to identify unique metabolic pathways. A metabolomic analysis was performed on human hPheo1 cells and shRNA SDHB knockdown hPheo1 (hPheo1 SDHB KD) cells. Additional analysis of 50 human fresh frozen PCC/PGL samples was conducted. Since the polyamine pathway surfaced in the metabolomics analysis, we hypothesized that treatment with polyamine inhibitors would be an effective option for aggressive PCC/PGL tumors. In vitro studies using N1,N11-diethylnorspermine (DENSPM) and N1,N12- diethylspermine (DESPM) treatments were carried out. DENSPM efficacy was assessed in xenograft models. Results: Components of the polyamine pathway were elevated in hPheo1 SDHB KD cells compared to wild-type cells. A similar observation was noted in SDHx PCC/PGLs tumor tissues compared to their SDHB wild-type counterparts. Specifically, spermidine, and spermine were significantly elevated in SDHx-mutated PCC/PGLs, with a similar trend in hPheo1 SDHB KD cells. Polyamine pathway inhibitors DENSPM and DESPM effectively inhibited growth of hPheo1 cells in vitro as well in mouse xenografts. Conclusions: This study demonstrates overactive polyamine pathway in PCC/PGL with SDHB mutations. Treatment with polyamine inhibitors significantly inhibited hPheo1 cell growth and led to growth inhibition in xenograft mouse models treated with DENSPM. These studies strongly implicate the polyamine pathway in PCC/PGL pathophysiology and provide new foundation for exploring the role for polyamine analogue inhibitors in treating metastatic PCC/PGL.

SAT-LB313 A Unicorn With Double Horns - Metastatic Paraganglioma in a Patient With Beckwith-Wiedemann Syndrome and Hereditary Paraganglioma Syndrome Iv

Introduction: Beckwith-Wiedemann syndrome (BWS), a multisystem genomic imprinting disorder in chromosome 11p15.5 region, is an overgrowth syndrome often presenting with macroglossia, abdominal wall defects, hemihyperplasia, enlarged abdominal organs and an increased risk of tumors including neuroblastoma, rhabdomyosarcoma, unilateral Wilm’s tumor, hepatoblastoma, adrenal cortical carcinoma and pheochromocytoma. Six cases of benign bilateral pheochromocytomas and one case of pheochromocytoma with lymph node metastasis in BWS have been described in the literature. We describe the first case of BWS with distant metastatic paraganglioma harboring an SDHB (succinate dehydrogenase subunit B) mutation. Presentation: A 28-year-old male with BWS whose history included an omphalocele and diaphragmatic hernia in infancy, neuroblastoma resected at age 2, and left carotid paraganglioma (PGL) resected at age 22 presented with abdominal pain. CT A/P with contrast revealed a 3.3 x 4.4 cm hypervascular mass and multiple bone metastases. Workup revealed normal plasma/urine metanephrines, elevated plasma dopamine of 178 pg/ml (normal <20) and elevated chromogranin A of 190 ng/ml (normal <90). 68Ga-dotatate PET CT showed hypermetabolic 4.4 cm mass (SUV 83), right hypopharynx mass (SUV 49), and many dota avid areas throughout the skeleton. The abdominal mass was resected and pathology was consistent with PGL. Due to unusual presentation, patient underwent hereditary cancer genetic testing (67 gene panel) and pathogenic mutation (c.713delT) in the SDHB gene was identified, consistent with hereditary PGL syndrome IV. Conclusion: While pheochromocytomas and other tumors are commonly found in association with BWS, PGLs are not. This is the first documented case of a patient with BWS having distant metastatic PGL. Malignant transformation of hereditary and sporadic pheochromocytomas and paraganglioma (PPGLs) is more common in SDHx associated PPGLs (>40% of metastatic PPGLs are related to an SDHB mutation). Hereditary PGL syndromes should be suspected in the case of PGLs that are recurrent, early onset (<45 years), extra-adrenal and/or metastatic. With additional genetic testing, our patient with an already rare growth disorder was found to have hereditary PGL syndrome IV caused by a pathogenic mutation in the SDHB gene. This unique case highlights the rationale and importance of systematic genetic cancer screening in the diagnostic evaluation of PPGLs.

Characterization of Malignant Head and Neck Paragangliomas at a Single Institution Across Multiple Decades

Malignant head and neck paragangliomas (HNPGLs) are rare entities, and there are limited data regarding optimal treatment recommendations to improve clinical outcomes. To classify succinate dehydrogenase (SDH) germline mutations associated with malignant HNPGLs, evaluate time from diagnosis to identification of malignant tumor, describe locations of metastases and the functional status of malignant HNPGLs, and determine the role of selective neck dissection at the time of initial surgical resection. A retrospective cohort study was completed of patients diagnosed with paragangliomas on various sites on the body at an academic tertiary cancer hospital between the years 1963 and 2018. A subanalysis of HNPGLs was also completed. Data regarding diagnosis, gene and mutation, tumor characteristics and location, and treatments used were reviewed between February 2017 and March 2018. Mutations of SDH genes associated with benign and malignant HNPGLs, treatments used, time to the discovery of malignancy, and location of metastasis. Of the 70 patients included in the study, 40 (57%) were male, and the mean (SD) age was 47 (21.1) years. Of patients with tumors isolated to the head and neck, 38 (54%) had benign HNPGLs, which were associated with mutations in the genes SDH subunit B (SDHB) (n = 18; 47%), SDH subunit C (n = 2; 5%), and SDH subunit D (n = 18; 47%). Among those with malignant HNPGLs, all but 1 patient had mutations in SDHB (n = 5; 83%); 1 patient had no mutation associated with their disease. The average age at diagnosis for malignant HNPGLs was 35 years, while benign tumors were diagnosed at an average age at 36 years. All patients with malignant disease underwent surgery. Four patients were found to have metastasis at the time of selective neck dissection. Among patients with malignant HNPGLs, 5 (83%) were treated with adjuvant radiation, and 1 (17%) was treated with adjuvant chemotherapy. Malignant HNPGLs are rare entities that are difficult to diagnose and are typically identified by the presence of regional or distant metastasis. The results of this study found the prevalence of malignant HNPGLs to be 9%. These data suggest that it is beneficial to perform a selective neck dissection at the time of tumor excision. All patients with malignant HNPGLs but 1 had SDHB mutations.

An analysis of surveillance screening for SDHB-related disease in childhood and adolescence.

ObjectivePhaeochromocytomas (PCC) and paragangliomas (PGL) are rare in children. A large proportion of these are now understood to be due to underlying germline mutations. Here we focus on succinate dehydrogenase subunit B (SDHB) gene mutation carriers as these tumours carry a high risk of malignant transformation. There remains no current consensus with respect to optimal surveillance for asymptomatic carriers and those in whom the presenting tumour has been resected.MethodWe undertook a retrospective analysis of longitudinal clinical data of all children and adolescents with SDHB mutations followed up in a single UK tertiary referral centre. This included index cases that pre-dated the introduction of surveillance screening and asymptomatic carriers identified through cascade genetic testing. We also conducted a literature review to inform a suggested surveillance protocol for children and adolescents harbouring SDHB mutations.ResultsClinical outcomes of a total of 38 children are presented: 8 index cases and 30 mutation-positive asymptomatic carriers with 175 patient years of follow-up data. Three of the eight index cases developed metachronous disease and two developed metastatic disease. Of the 30 asymptomatic carriers, 3 were found to have PGLs on surveillance screening.ConclusionsSurveillance screening was well tolerated in our paediatric cohort and asymptomatic paediatric subjects. Screening can identify tumours before they become secretory and/or symptomatic, thereby facilitating surgical resection and reducing the chance of distant spread. We propose a regular screening protocol commencing at age 5 years in this at-risk cohort of patients.

Targeting NAD+/PARP DNA Repair Pathway as a Novel Therapeutic Approach to SDHB-Mutated Cluster I Pheochromocytoma and Paraganglioma

Purpose: Cluster I pheochromocytomas and paragangliomas (PCPGs) tend to develop malignant transformation, tumor recurrence, and multiplicity. Transcriptomic profiling suggests that cluster I PCPGs and other related tumors exhibit distinctive changes in the tricarboxylic acid (TCA) cycle, the hypoxia signaling pathway, mitochondrial electron transport chain, and methylation status, suggesting that therapeutic regimen might be optimized by targeting these signature molecular pathways.Experimental Design: In the present study, we investigated the molecular signatures in clinical specimens from cluster I PCPGs in comparison with cluster II PCPGs that are related to kinase signaling and often present as benign tumors.Results: We found that cluster I PCPGs develop a dependency to mitochondrial complex I, evidenced by the upregulation of complex I components and enhanced NADH dehydrogenation. Alteration in mitochondrial function resulted in strengthened NAD+ metabolism, here considered as a key mechanism of chemoresistance, particularly, of succinate dehydrogenase subunit B (SDHB)-mutated cluster I PCPGs via the PARP1/BER DNA repair pathway. Combining a PARP inhibitor with temozolomide, a conventional chemotherapeutic agent, not only improved cytotoxicity but also reduced metastatic lesions, with prolonged overall survival of mice with SDHB knockdown PCPG allograft.Conclusions: In summary, our findings provide novel insights into an effective strategy for targeting cluster I PCPGs, especially those with SDHB mutations. Clin Cancer Res; 24(14); 3423-32. ©2018 AACR.

Extent of surgery for phaeochromocytomas in the genomic era.

Germline mutations are present in 20-30 per cent of patients with phaeochromocytoma. For patients who develop bilateral disease, complete removal of both adrenal glands (total adrenalectomy) will result in lifelong adrenal insufficiency with an increased risk of death from adrenal crisis. Unilateral/bilateral adrenal-sparing surgery (subtotal adrenalectomy) offers preservation of cortical function and independence from steroids, but leaves the adrenal medulla in situ and thus at risk of developing new and possibly malignant disease. Here, present knowledge about how tumour genotype relates to clinical behaviour is reviewed, and application of this knowledge when choosing the extent of adrenalectomy is discussed. A literature review was undertaken of the penetrance of the different genotypes in phaeochromocytomas, the frequency of bilateral disease and malignancy, and the underlying pathophysiological mechanisms, with emphasis on explaining the clinical phenotypes of phaeochromocytomas and their associated syndromes. Patients with bilateral phaeochromocytomas most often have multiple endocrine neoplasia type 2 (MEN2) or von Hippel-Lindau disease (VHL) with high-penetrance mutations for benign disease, whereas patients with mutations in the genes encoding SDHB (succinate dehydrogenase subunit B) or MAX (myelocytomatosis viral proto-oncogene homologue-associated factor X) are at increased risk of malignancy. Adrenal-sparing surgery should be the standard approach for patients who have already been diagnosed with MEN2 or VHL when operating on the first side, whereas complete removal of the affected adrenal gland(s) is generally recommended for patients with SDHB or MAX germline mutations. Routine assessment of a patient's genotype, even after the first operation, can be crucial for adopting an appropriate strategy for follow-up and future surgery.

SDHB-related pheochromocytoma and paraganglioma penetrance and genotype-phenotype correlations.

Succinate dehydrogenase subunit B (SDHB) gene mutations are associated with an aggressive clinical disease course of pheochromocytoma/paraganglioma (PHEO/PGL). Limited information is available concerning PHEO/PGL penetrance among SDHB mutation carriers with regards to primary tumor location, specific mutation type, and gender. We assessed PHEO/PGL penetrance in SDHB mutation carriers and described the clinical presentation and disease course. Asymptomatic relatives (N = 611) of 103 index patients were tested for SDHB mutations. Mutation carriers (N = 328) were offered PHEO/PGL screening, of which 241 participated and were included in penetrance analysis. For additional disease outcome analysis, the 103 index patients and 40 screened individuals who developed PHEO/PGL were included. Clinical data were collected between October 2004 and June 2016. Forty (16.60%) of the 241 screened individuals developed PHEO/PGL during the study. The penetrance estimate in this population was 49.80% (95% CI 29-74.9) at 85years. A significantly higher age-related penetrance of disease was observed in males compared to females, with 50% penetrance achieved at age 74 vs. not reached. Age-related penetrance analysis demonstrated 4 mutations (Ile127Ser, IVS1+1G>T, Exon 1 deletion, Arg90X) presenting with a slower rate of disease development (50% penetrance ages, respectively: not achieved, 70, 63, 61years) compared to Arg46X and Val140Phe mutations (50% penetrance at 38years). Here, we found a higher estimated penetrance compared to several other studies, and a striking difference in age-related penetrance between male and female SDHB mutation carriers with no association between mutation and gender or tumor location.

Pituitary Carcinoma in a Patient with an SDHB Mutation

We present the first case of pituitary carcinoma occurring in a patient with a succinate dehydrogenase subunit B (SDHB) mutation and history of paraganglioma. She was initially treated for a glomus tumour with external beam radiotherapy. Twenty-five years later, she was diagnosed with a non-functioning pituitary adenoma, having developed bitemporal hemianopia. Recurrence of the pituitary lesion (Ki-67 10% and p53 overexpressed) occurred 5 years after her transsphenoidal surgery, for which she underwent two further operations followed by radiotherapy. Histology showed large cells with vacuolated clear cytoplasm with positive immunostaining for steroidogenic factor 1 (SF1) and negative staining for pituitary hormones. Four years after the pituitary radiotherapy, two metastatic deposits were identified: a foramen magnum lesion and an intradural extra-medullary cervical lesion at the level of C3/C4. There was also significant growth of the primary pituitary lesion with associated visual deterioration. A biopsy of the foramen magnum lesion, demonstrating cells with vacuolated, clear cytoplasm and positive SF1 staining confirmed a pituitary carcinoma, for which she was commenced on temozolomide chemotherapy. There was dramatic clinical improvement after three cycles and reduction in the size of the lesions was observed following six cycles of temozolomide, and further shrinkage after 10 cycles. The plan is for a total of 12 cycles of temozolomide chemotherapy. SDH mutation-related pituitary tumours have an aggressive phenotype which, in this case, led to metastatic disease. SF1 immunostaining was helpful to identify the tissue origin of the metastatic deposit and to confirm the pituitary carcinoma.

Succinate dehydrogenase subunit-B mutation with associated prolactinoma and typical carcinoids

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Outcomes of annual surveillance imaging in an adult and paediatric cohort of succinate dehydrogenase B mutation carriers.

For 'asymptomatic carriers' of the succinate dehydrogenase subunit B (SDHB) gene mutations, there is currently no consensus as to the appropriate modality or frequency of surveillance imaging. We present the results of a surveillance programme of SDHB mutation carriers. Review of clinical outcomes of a surveillance regimen in patients identified to have an SDHB gene mutation, based on annual MRI, in a single UK tertiary referral centre. A total of 92 patients were identified with an SDHB gene mutation. a total of 27 index patients presented with symptoms, and 65 patients were identified as asymptomatic carriers. Annual MRI of the abdomen, with alternate year MRI of the neck, thorax and pelvis. Presence of an SDHB-related tumour included paraganglioma (PGL), phaeochromocytoma (PCC), renal cell carcinoma (RCC) and gastrointestinal stromal tumour (GIST). A total of 43 PGLs, eight PCCs and one RCC occurred in the 27 index patients (23 solitary, four synchronous, five metachronous). A further 15 SDHB-related tumours (11 PGLs, three RCCs, one GIST) were identified in the asymptomatic carriers on surveillance screening (25% of screened carriers): 10 on the first surveillance imaging and five on subsequent imaging 2-6 years later. A total of 11 patients had malignant disease. SDHB-related tumours are picked up as early as 2 years after initial negative surveillance scan. We believe the high malignancy rate and early identification rate of tumours justifies the use of 1-2 yearly imaging protocols and MRI-based imaging could form the mainstay of surveillance in this patient group thereby minimizing radiation exposure.

Calculating the optimal surveillance for head and neck paraganglioma in SDHB-mutation carriers

Germline mutations of the gene encoding succinate dehydrogenase subunit B (SDHB) predispose to head-and-neck-paraganglioma (HNPGL), sympathetic PGL, pheochromocytoma and renal cell carcinoma for which regular surveillance is required. SDHB-associated tumors harbor germline and somatic mutations, consistent with Knudson’s two-hit hypothesis. To assess the penetrance and optimal surveillance for different manifestations of SDHB mutation carriers. This study included all SDHB mutation carriers who were followed at the Department of Endocrinology at the University Medical Center of Groningen. Kaplan–Meier curves were used to assess the penetrance. Poisson process was used to assess the optimal age to start surveillance and intervals. Ninety-one SDHB-mutation carriers (38 men and 53 women) were included. Twenty-seven mutation carriers (30 %) had manifestations, with an overall penetrance 35 % at the age of 60 years. We calculated that optimal surveillance for HNPGL could start from an age of 27 years with an interval of 3.2 years. This study underscores the relatively low penetrance of disease in SDHB mutation carriers. Use of the Poisson approach provides a more accurate estimation of the age to initiate surveillance and length of intervals for HNPGL. These results may give rise to reconsider the current guidelines regarding the screening of these mutation carriers.

Renal Cell Carcinoma Occurring in Patients With Prior Neuroblastoma: A Heterogenous Group of Neoplasms.

Renal cell carcinoma (RCC) associated with neuroblastoma (NB) was included as a distinct entity in the 2004 World Health Organization classification of kidney tumors. A spectrum of RCC subtypes has been reported in NB survivors. We herein describe a series of 8 RCCs diagnosed in 7 patients with a history of NB. Microscopic evaluation, immunohistochemical staining for PAX8, cathepsin K, and succinate dehydrogenase subunit B (SDHB), and fluorescence in situ hybridization (FISH) for TFE3 and TFEB were performed. Four distinct morphologic subtypes were identified: 3 tumors were characterized by cells with abundant oncocytoid cytoplasm and irregular nuclei; 3 showed features of microphthalmia transcription factor family translocation RCC (MiTF-RCC); 1 had features of hybrid oncocytic-chromophobe tumor; 1 had papillary RCC histology. All RCCs expressed PAX8 and retained SDHB expression. Cathepsin K was positive in 2 MiTF-RCCs, 1 was TFEB FISH positive, and the other was indeterminate. Cathepsin K was negative in a third MiTF-RCC with TFE3 rearrangement. TFE3 FISH was negative in 4 and insufficient in 1 of the other 5 RCCs. While a subset of RCCs associated with NB is characterized by cells with prominent oncocytoid cytoplasm, other RCC subtypes also occur in post-NB patients. Renal neoplasms occurring in patients with a history of NB do not represent a single entity but a heterogenous group of RCCs. SDHB mutations do not explain the subset of nontranslocation RCCs with oncocytoid features; therefore, further studies are needed to clarify whether they may represent a distinct entity with unique molecular abnormalities or may belong to other emerging RCC subtypes.