Genetics of pheochromocytoma and paraganglioma

Genetic landscape of Romanian PPGLs

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumours that originate from chromaffin cells and occur in the adrenal medulla and in the sympathetic or parasympathetic ganglia. Nearly 70% of PPGLs result from germline or somatic mutations in a single driver gene. The aim of this study was to characterize the genetic background and clinical characteristics related to genetic profile of patients with PPGLs from Romania. We retrospectively retrieved data of 125 patients consecutively registered, diagnosed with PPGLs in a tertiary referral center of endocrinology from Romania, between 1976 and 2022. We identified 88 (70.4%) women, and 37 (29.6%) men, with a mean age at diagnosis of 48.5 ± 15 years. From these 125 patients, 80 (64%) were submitted to the genomic study; 35% (n = 28) had a germline mutation (20 RET, 3 VHL, 1 SDHB, 1 NF1, 1 SDHD, 1 FANCA, 1 CASR) while 65% (n = 52) presented sporadic disease. Patients with hereditary disease had significantly lower age at diagnosis comparing to sporadic cases (37 ± 15 vs. 49.9 ± 12.2 years, p = 0.001). Bilateral tumors developed in twelve patients from the hereditary group. Metastatic disease was described in 4 out of 80 patients (2 of them with hereditary disease). Patients from sporadic group tended to have a right lateralisation of the tumour compared to hereditary cases, where the tumour was more often left sided. RET pathogenic variant (p.Cys634Trp) associated with MEN2A syndrome was the most prevalent in Romanian population with PPGLs and could be considered as a founder effect. Patients with hereditary disease are diagnosed at a younger age and develop bilateral tumors more frequently compared to sporadic cases.

Clinical Review: The Approach to the Evaluation and Management of Bilateral Adrenal Masses

OBJECTIVE

This white paper provides practical guidance for clinicians encountering bilateral adrenal masses.

METHODS

A case-based approach to the evaluation and management of bilateral adrenal masses. Specific clinical scenarios presented here include cases of bilateral adrenal adenomas, hemorrhage, pheochromocytomas, metastatic disease, myelolipomas, as well as primary bilateral macronodular adrenal hyperplasia.

RESULTS

Bilateral adrenal masses represent approximately 10% to 20% of incidentally discovered adrenal masses. The general approach to the evaluation and management of bilateral adrenal masses follows the same protocol as the evaluation of unilateral adrenal masses, determined based on the patient's clinical history and examination as well as the imaging characteristics of each lesion, whether the lesions could represent a malignancy, demonstrate hormone excess, or possibly represent a familial syndrome. Furthermore, there are features unique to bilateral adrenal masses that must be considered, including the differential diagnosis, the evaluation, and the management depending on the etiology. Therefore, considerations for the optimal imaging modality, treatment (medical vs surgical therapy), and surveillance are included. These recommendations were developed through careful examination of existing published studies as well as expert clinical opinion consensus.

CONCLUSION

The evaluation and management of bilateral adrenal masses require a comprehensive systematic approach which includes the assessment and interpretation of the patient's clinical history, physical examination, dynamic hormone evaluation, and imaging modalities to determine the key radiographic features of each adrenal nodule. In addition, familial syndromes should be considered. Any final treatment options and approaches should always be considered individually.

Management of Pheochromocytomas and Paragangliomas

Pheochromocytomas and paragangliomas are distinctive neuroendocrine tumors which frequently produce excess catecholamines with resultant cardiovascular morbidity. These tumors have a strong genetic component, with up to 40% linked to hereditary pathogenic variants; therefore, germline genetic testing is recommended for all patients. Surgical resection offers the only potential cure in the case of localized disease. Given the potential for catecholaminergic crises, appropriate perioperative management is crucial, and all patients should undergo alpha-adrenergic blockade before resection. Therapeutic options for metastatic disease are limited and include surgical debulking, radiopharmaceutical therapies, and conventional chemotherapy.

[Diagnosis and management of patients with pheochromocytoma/paraganglioma: Consensus of experts of the Russian Medical Society for Arterial Hypertension and the Multidisciplinary Group for the Diagnosis and Treatment of Neuroendocrine Tumors]

The understanding of the nature of catecholamine-secreting tumors has changed significantly in recent years, affecting terminology and classification. Phaeochromocytoma/paraganglioma (PCC/PG) is a rare neuroendocrine tumor from chromaffin tissue that produces and secretes catecholamines. The incidence of PCC/PG is relatively low, with 2-8 cases per 1 million population per year; among patients with arterial hypertension, their prevalence is 0.2-0.6%. However, delayed diagnosis of PCC/PG is associated with a high risk of cardiovascular complications and a high mortality rate. The consensus presents the clinical manifestations of the disease with an emphasis on the course of arterial hypertension as the most common symptom in PCC/PG; modern ideas about the features of diagnosis, aspects of preoperative preparation, treatment, and follow-up of patients with PCC/PG are considered.

Analysis of clinical and pathological characteristics of retroperitoneal paraganglioma and associated prognostic factors

BACKGROUND AND OBJECTIVES

The aim of this study is to explore the long-term prognostic risk factors associated with patients diagnosed with retroperitoneal paraganglioma (RPGL) and examine their clinical and pathological characteristics.

METHODS

Expressions of biomarkers were identified using immunohistochemistry (IHC) and case databases were retrospectively searched. Survival analysis was performed using Kaplan-Meier and Cox risk regression to identify the factors that influence the postoperative progression-free survival of patients with RPGL.

RESULTS

A total of 105 patients, most of whom had tumors situated in the paraaortic region, and whose average tumor size was 8.6 cm, were enrolled in this study. The average follow-up duration was 51 months, with a mortality rate of 19% and a recurrence and metastasis rate of 41.9%. Tumors were assessed using the modified Grading system for Adrenal Pheochromocytoma and Paraganglioma (GAPP), and SDHB, S-100, and Ki-67 were stained using IHC in all cases. Out of the total cases examined, negative in SDHB expression were observed in 18.1% of cases, S-100 expression was negative in 36.2% of cases, and endovascular tumor enboluswas present in approximately 25.7% of cases. The results of the univariate analysis indicated that several factors significantly influenced the progression-free survival of patients with PGL as follow: maximum tumor diameter (>5.5 cm), tumor morphological features, tumor grading (modified GAPP score > 6), SDHB negative, S-100 negative, and expression of proliferation index Ki-67 (>3%) (X2 = 4.217-27.420, p < 0.05). The results of the multivariate analysis indicated that negative of S-100 (p = 0.021) and SDHB (p = 0.038), as well as intravascular tumor thrombus (p = 0.047) expression were independent risk factors for progression-free survival in patients.

CONCLUSION

RPGL is characterized by diverse biological features and an elevated susceptibility to both recurrence and metastasis. Both SDHB and S-100 can be employed as traditional IHC indicators to predict the metastatic risk of PGL, whereas the tumor histomorphology-endovascular tumor enbolus assists in determining the metastasis risk of RPGL.

Challenges in genetic screening for inherited endocrinopathy affecting the thyroid, parathyroid and adrenal glands in Singapore

Significant progress has been made in the understand-ing of many human diseases, especially cancers, which has contributed to improved and increased survival. The Human Genome Project and The Cancer Genome Atlas project brought about a new era, with an understanding of inherited diseases at a molecular level, which subsequently facilitated the option of precision medicine. Precision medicine has helped tailor treatment decisions at an individual level, for instance in terms of surgical treatments or targeted therapies in advanced diseases. Despite the increasing advances in genetic-lead precision medicine, this has not translated into increasing uptake among patients. Reasons for this may be potential knowledge gaps among clinicians; on reasons for poor uptake of genetic testing such as for cultural, religious or personal beliefs; and on financial implications such as lack of support from insurance companies. In this review, we look at the current scenario of genetic screening for common inherited endocrine conditions affecting the thyroid, parathyroid and adrenal glands in Singapore, and the implications associated with it.

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

OBJECTIVE

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.

DESIGN

This is a retrospective analysis of treatment responses of mPPGL patients (n = 74) to systemic therapies.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Total adrenalectomy versus subtotal adrenalectomy for bilateral pheochromocytoma: meta-analysis

BACKGROUND

Bilateral pheochromocytomas are rare and often heritable. Total adrenalectomy leads to a definitive oncological cure, with subsequent definitive hypocortisolism. Subtotal adrenalectomy is a possible alternative. The aim of this study was to assess the effects of total adrenalectomy and subtotal adrenalectomy on bilateral pheochromocytoma in terms of post-surgical rate of recurrence, metastatic disease, and steroid dependence.

METHODS

Systematic searches in the bibliographic databases PubMed, Embase, and Europe PMC were performed for 1945 to 1 June 2023. PRISMA guidelines were followed and the PICO strategy was applied to English-language studies comparing subtotal adrenalectomy with total adrenalectomy. A random-effects model was used to assess the different outcomes for studies with high heterogeneity. The Newcastle-Ottawa scale and the Risk Of Bias In Non-randomized Studies of Interventions ('ROBINS-I') tool were used to assess quality and risk of bias.

RESULTS

From a total of 12 909 studies, 1202 patients (from 10 retrospective studies) were eligible for the meta-analysis. In six studies, including 1176 patients, the recurrence rate after subtotal adrenalectomy and total adrenalectomy was 14.1 versus 2.6 per cent respectively (OR 4.91, 95 per cent c.i. 1.30 to 18.54; P = 0.020; I2 72 per cent). In nine studies, including 1124 patients, the rate of post-surgical steroid dependence was 93.3 versus 11.6 per cent after total adrenalectomy and subtotal adrenalectomy respectively (OR 0.003, 95 per cent c.i. 0.0003 to 0.03; P < 0.00001; I2 66 per cent). Based on two studies, including 719 patients, no differences were evident regarding the occurrence of post-surgery metastatic disease.

CONCLUSION

Subtotal adrenalectomy leads to less post-surgical primary adrenal insufficiency, but leads to a higher postoperative recurrence rate. Future prospective randomized studies, with clear eligibility criteria, are needed to confirm these results.

PD-L1 and HIF-2α Upregulation in Head and Neck Paragangliomas after Embolization

Hypoxia activates pathways associated with tumor progression, metastatic spread, and alterations in the immune microenvironment leading to an immunosuppressive phenotype. In particular, the upregulation of PD-L1, a target for therapy with checkpoint inhibitors, is well-studied in several tumors. However, the relationship between hypoxia and PD-L1 regulation in pheochromocytomas and paragangliomas (PPGL), and especially in paragangliomas treated with embolization, is still largely unexplored. We investigated the expression of the hypoxia-marker HIF-2α and of PD-L1 in a PPGL-cohort with and without embolization as potential biomarkers that may predict the response to treatment with HIF-2α and checkpoint inhibitors. A total of 29 tumor samples from 25 patients who were operated at a single center were included and analyzed utilizing immunohistochemistry (IHC) for PD-L1 and HIF-2α. Embolization prior to surgery was performed in seven (24%) tumors. PD-L1 expression in tumor cells of head and neck paragangliomas (HNPGLs) receiving prior embolization (median PD-L1 positivity: 15%) was significantly higher as compared to PD-L1 expression in HNPGLs without prior embolization (median PD-L1 positivity: 0%) (p = 0.008). Consistently, significantly more HNPGLs with prior embolization were positive for HIF-2α (median nuclear HIF-2α positivity: 40%) as compared to HNPGLs without prior embolization (median nuclear HIF-2α positivity: 0%) (p = 0.016). Our results support the hypothesis that embolization with subsequent hypoxia leads to the upregulation of both PD-L1 and HIF-2α in HNPGLs, and could thus facilitate targeted treatment with HIF-2α and checkpoint inhibitors in the case of inoperable, locally advanced, or metastatic disease.

Report of a vagal paraganglioma at the cervicothoracic junction

BACKGROUND

Vagus nerve paragangliomas are rare tumors, comprising 0.03% of head and neck neoplasms. These tumors are usually located cephalad to the hyoid bone, and there is only one previously reported case that arose from the lower third of the neck.

METHODS

We describe the second reported case of a lower neck vagus nerve paraganglioma that was managed with a limited sternotomy for access and surgical removal.

RESULTS

A 66-year-old male presented with a long-standing lesion of the cervicothoracic junction. CT, MRI, and Ga-68 DOTATATE PET/CT showed an avidly enhancing 5.2 × 4.2 × 11.5 cm mass extending from C6 to approximately T4 level. FNA confirmed the diagnosis. The patient underwent catheter angiography and embolization via direct puncture technique followed by excision of the mass via a combined transcervical and limited sternotomy approach.

CONCLUSION

We describe an unusual case of vagal paraganglioma at the cervicothoracic junction with retrosternal extension requiring a sternotomy for surgical excision.

Metastatic Pheochromocytoma and Paraganglioma: Somatostatin Receptor 2 Expression, Genetics, and Therapeutic Responses

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) with pathogenic mutations in the succinate dehydrogenase subunit B (SDHB) are associated with a high metastatic risk. Somatostatin receptor 2 (SSTR2)-dependent imaging is the most sensitive imaging modality for SDHB-related PPGLs, suggesting that SSTR2 expression is a significant cell surface therapeutic biomarker of such tumors.

OBJECTIVE

Exploration of the relationship between SSTR2 immunoreactivity and SDHB immunoreactivity, mutational status, and clinical behavior of PPGLs. Evaluation of SSTR-based therapies in metastatic PPGLs.

METHODS

Retrospective analysis of a multicenter cohort of PPGLs at 6 specialized Endocrine Tumor Centers in Germany, The Netherlands, and Switzerland. Patients with PPGLs participating in the ENSAT registry were included. Clinical data were extracted from medical records, and immunohistochemistry (IHC) for SDHB and SSTR2 was performed in patients with available tumor tissue. Immunoreactivity of SSTR2 was investigated using Volante scores. The main outcome measure was the association of SSTR2 IHC positivity with genetic and clinical-pathological features of PPGLs.

RESULTS

Of 202 patients with PPGLs, 50% were SSTR2 positive. SSTR2 positivity was significantly associated with SDHB- and SDHx-related PPGLs, with the strongest SSTR2 staining intensity in SDHB-related PPGLs (P = .01). Moreover, SSTR2 expression was significantly associated with metastatic disease independent of SDHB/SDHx mutation status (P < .001). In metastatic PPGLs, the disease control rate with first-line SSTR-based radionuclide therapy was 67% (n = 22, n = 11 SDHx), and with first-line "cold" somatostatin analogs 100% (n = 6, n = 3 SDHx).

CONCLUSION

SSTR2 expression was independently associated with SDHB/SDHx mutations and metastatic disease. We confirm a high disease control rate of somatostatin receptor-based therapies in metastatic PPGLs.

Case Report: A novel EPAS1 mutation in a case of paraganglioma complicated with polycythemia and atrial septal defect

Background

Paraganglioma is a rare neuroendocrine tumor and is highly associated with hereditary susceptibility genes, often occurring as part of a genetic syndrome. The genetic heterogeneity of paraganglioma poses challenges in diagnosis, counseling, and clinical management.

Case summary

We present the case of a 60-year-old woman with hypertension, atrial septal defect, and polycythemia, who experienced paroxysmal palpitations, sweating, headache, abdominal pain, nausea, and vomiting. Her blood pressure was severely unstable. Blood laboratory tests revealed elevated catecholamine levels, contrast-enhanced CT of her whole abdomen showed a round retroperitoneal mass with soft tissue density, and somatostatin receptor imaging (68Ga PET-CT) indicated a retroperitoneal mass with abnormally increased expression of somatostatin receptor. It is interesting to note that whole exome sequencing (WES) analyses on both blood and tumor samples revealed a novel EPAS1 mutation, specifically the c.2501A > G; p.Tyr834Cys variant, which has never been reported. The patient was diagnosed with paraganglioma and underwent successful Da Vinci robot-assisted laparoscopic resection of the retroperitoneal tumor. During a 3-month follow-up period, her blood pressure stabilized, and her symptoms significantly improved.

Conclusion

This case reveals that the EPSA1 mutation may be the primary driver of paraganglioma complicated by atrial septal defect and polycythemia. Additionally, the utilization of Da Vinci robot-assisted laparoscopic surgery contributed to a favorable prognosis for the patient.

Cytoplasmic HIF-2α as tissue biomarker to identify metastatic sympathetic paraganglioma

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare neuroendocrine tumors. PGLs can further be divided into sympathetic (sPGLs) and head-and-neck (HN-PGLs). There are virtually no treatment options, and no cure, for metastatic PCCs and PGLs (PPGLs). Here, we composed a tissue microarray (TMA) consisting of 149 PPGLs, reflecting clinical features, presenting as a useful resource. Mutations in the pseudohypoxic marker HIF-2α correlate to an aggressive tumor phenotype. We show that HIF-2α localized to the cytoplasm in PPGLs. This subcompartmentalized protein expression differed between tumor subtypes, and strongly correlated to proliferation. Half of all sPGLs were metastatic at time of diagnosis. Cytoplasmic HIF-2α was strongly expressed in metastatic sPGLs and predicted poor outcome in this subgroup. We propose that higher cytoplasmic HIF-2α expression could serve as a useful clinical marker to differentiate paragangliomas from pheochromocytomas, and may help predict outcome in sPGL patients.

The role of fibroblast growth factor 18 in cancers: functions and signaling pathways

Fibroblast growth factor 18(FGF18) is a member of the fibroblast growth factor family (FGFs). FGF18 is a class of bioactive substances that can conduct biological signals, regulate cell growth, participate in tissue repair and other functions, and can promote the occurrence and development of different types of malignant tumors through various mechanisms. In this review, we focus on recent studies of FGF18 in the diagnosis, treatment, and prognosis of tumors in digestive, reproductive, urinary, respiratory, motor, and pediatric systems. These findings suggest that FGF18 may play an increasingly important role in the clinical evaluation of these malignancies. Overall, FGF18 can function as an important oncogene at different gene and protein levels, and can be used as a potential new therapeutic target and prognostic biomarker for these tumors.

Co-occurrence of mutations in NF1 and other susceptibility genes in pheochromocytoma and paraganglioma

Introduction

The percentage of patients diagnosed with pheochromocytoma and paraganglioma (altogether PPGL) carrying known germline mutations in one of the over fifteen susceptibility genes identified to date has dramatically increased during the last two decades, accounting for up to 35-40% of PPGL patients. Moreover, the application of NGS to the diagnosis of PPGL detects unexpected co-occurrences of pathogenic allelic variants in different susceptibility genes.

Methods

Herein we uncover several cases with dual mutations in NF1 and other PPGL genes by targeted sequencing. We studied the molecular characteristics of the tumours with co-occurrent mutations, using omic tools to gain insight into the role of these events in tumour development.

Results

Amongst 23 patients carrying germline NF1 mutations, targeted sequencing revealed additional pathogenic germline variants in DLST (n=1) and MDH2 (n=2), and two somatic mutations in H3-3A and PRKAR1A. Three additional patients, with somatic mutations in NF1 were found carrying germline pathogenic mutations in SDHB or DLST, and a somatic truncating mutation in ATRX. Two of the cases with dual germline mutations showed multiple pheochromocytomas or extra-adrenal paragangliomas - an extremely rare clinical finding in NF1 patients. Transcriptional and methylation profiling and metabolite assessment showed an "intermediate signature" to suggest that both variants had a pathological role in tumour development.

Discussion

In conclusion, mutations affecting genes involved in different pathways (pseudohypoxic and receptor tyrosine kinase signalling) co-occurring in the same patient could provide a selective advantage for the development of PPGL, and explain the variable expressivity and incomplete penetrance observed in some patients.

A genomic deep field view of hypertension

Blood pressure is regulated by a complex neurohumoral system including the renin-angiotensin-aldosterone system, natriuretic peptides, endothelial pathways, the sympathetic nervous system, and the immune system. This review charts the evolution of our understanding of the genomic basis of hypertension at increasing resolution over the last 5 decades from monogenic causes to polygenic associations, spanning ∼30 monogenic rare variants and >1500 single nucleotide variants. Unexpected early wins from blood pressure genomics include deepening of our understanding of the complex causation of hypertension; refinement of causal estimates bidirectionally between blood pressure, risk factors, and outcomes through Mendelian randomization; risk stratification using polygenic risk scores; and opportunities for precision medicine and drug repurposing.

Pheochromocytoma recurrence in hereditary disease: does a cortical-sparing technique increase recurrence rate?

BACKGROUND

Posterior retroperitoneoscopic adrenalectomy is an appealing approach for patients with hereditary pheochromocytoma and lends well to cortex preservation. We sought to examine pheochromocytoma recurrence in patients with hereditary pheochromocytoma in the era of posterior retroperitoneoscopic adrenalectomy and evaluate the predictors of recurrence.

METHODS

Patients with hereditary pheochromocytoma who underwent adrenalectomy for pheochromocytoma between 1995 and 2020 with biochemical cure and follow-up >1 year were identified. Recurrence was defined as plasma metanephrines above the upper limit of normal with radiographic evidence of disease in the ipsilateral adrenal bed.

RESULTS

Seventy-eight hereditary pheochromocytoma patients (median age = 32.4 years; 60.3% women) underwent 114 adrenalectomies for pheochromocytoma. Of these patients, 40 had multiple endocrine neoplasia type 2A (51.3%), 10 had multiple endocrine neoplasia type B (12.8%), 17 had von Hippel-Lindau disease (21.8%), and 11 had neurofibromatosis type 1 (14.1%). Thirty-eight adrenalectomies (33.3%) were performed before the introduction of posterior retroperitoneoscopic adrenalectomy and 76 (66.7%) after. Cortical-sparing technique was performed in 62 (54.4%) adrenalectomies, with no difference in its use before and after posterior retroperitoneoscopic adrenalectomy introduction (P > .05). During a median follow-up of 80.7 months (interquartile range 43.4-151.2), 12 ipsilateral recurrences (10.5%) were identified. There was no difference in recurrence before and after the introduction of posterior retroperitoneoscopic adrenalectomy or by surgical technique or approach of the entire cohort (P > .05). Recurrence was more common in those with RET M918T mutation (23.5% vs 8.2%; P = .05). Patients with RET M918T mutations had a shorter recurrence-free survival (P = .013). On multivariate analysis, only RET M918T mutation was independently associated with an increased recurrence risk (hazard ratio = 4.30; 95% confidence interval, 1.26-14.66; P = .019).

CONCLUSION

The introduction of posterior retroperitoneoscopic adrenalectomy did not influence the recurrence rate after adrenalectomy for hereditary pheochromocytoma patients. Patients with a RET M918T germline mutation are at increased risk for pheochromocytoma recurrence and may benefit from initial total adrenalectomy.

PD-L1 expression and association with genetic background in pheochromocytoma and paraganglioma

Metastatic pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors associated with poor prognosis and limited therapeutic options. Recent advances in oncology-related immunotherapy, specifically in targeting of programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) pathways, have identified a new treatment potential in a variety of tumors, including advanced and rare tumors. Only a fraction of patients being treated by immune checkpoint inhibitors have shown to benefit from it, displaying a need for strategies which identify patients who may most likely show a favorable response. Building on recent, promising outcomes in a clinical study of metastatic PPGL using pembrolizumab, a humanized IgG4κ monoclonal antibody targeting the PD-1/PD-L1 pathway, we examined PD-L1 and PD-L2 expression in relation to oncogenic drivers in our PPGL patient cohort to explore whether expression can predict metastatic potential and/or be considered a predictive marker for targeted therapy. We evaluated RNA expression in the NIH cohort of 48 patients with known genetic predisposition (sporadic; pseudohypoxia: SDHB, VHL, EPAS1, EGLN1; kinase signaling: RET, NF1) and 6 normal medulla samples (NAM). For comparison, 72 PPGL samples from The Cancer Genome Atlas (TCGA) were used for analysis of gene expression based on the variant status (pseudohypoxia: SDHB, VHL, EPAS1, EGLN1; kinase signaling: NF1, RET). Expression of PD-L1 was elevated in the PPGL cohort compared to normal adrenal medulla, aligning with the TCGA analysis, whereas PD-L2 was not elevated. However, expression of PD-L1 was lower in the pseudohypoxia cluster compared to the sporadic and the kinase signaling subtype cluster, suggesting that sporadic and kinase signaling cluster PPGLs could benefit from PD-1/PD-L1 therapy more than the pseudohypoxia cluster. Within the pseudohypoxia cluster, expression of PD-L1 was significantly lower in both SDHB- and non-SDHB-mutated tumors compared to sporadic tumors. PD-L1 and PD-L2 expression was not affected by the metastatic status. We conclude that PD-L1 and PD-L2 expression in our cohort of PPGL tumors was not linked to metastatic behavior, however, the presence of PPGL driver mutation could be a predictive marker for PD-L1-targeted therapy and an important feature for further clinical studies in patients with PPGL.

The immune cell infiltrate in the tumour microenvironment of phaeochromocytomas and paragangliomas

Emerging evidence suggests the composition of the tumour microenvironment (TME) correlates with clinical outcome and that each tumour type has a unique TME including a variable population of inflammatory cells. We performed immunohistochemistry on 65 phaeochromocytoma and paraganglioma (PPGL) tumour samples with 20 normal adrenal medulla samples for comparison. The immune cells assessed were macrophages, lymphocytes and neutrophils, and we compared the proportion of infiltration of these immune cells with clinical and histopathological factors. There was a higher proportion of immune cells in tumour tissue compared to non-neoplastic adrenal medulla tissue, with a predominance of macrophages. There was a higher proportion of M2:M1 macrophages and T-helper lymphocytes in aggressive tumours compared to indolent ones. For SDHB-associated tumours, there was a higher proportion of M2 macrophage infiltration, with higher M2:M1 in aggressive SDHB PPGLs compared to indolent tumours. These data demonstrate that immune cells do infiltrate the TME of PPGLs, confirming that PPGLs are immunologically active tumours. Differences in the TME of PPGLs were observed between aggressive and indolent tumours. These differences could potentially be exploited as an aid in predicting tumour behaviour.

Fumarate hydratase gene germline variants and mosaicism associated with pheochromocytoma and paraganglioma

Fumarate hydratase (FH) catalyzes the conversion of fumaric acid to L-malic acid. Heterozygous variants of the human fumarate hydratase gene (FH) predispose to hereditary leiomyomatosis and renal cell cancer and, rarely, pheochromocytoma/paraganglioma (PPGL). No mosaic variant in FH has been reported yet. Using next-generation sequencing, five individuals with FH variants were found in 319 PPGL patients. Immunohistochemistry staining and loss of heterozygosity analysis in tumor tissues were performed to determine the pathogenicity of the variants. Deep targeted sequencing was performed on the peripheral blood DNA of a pheochromocytoma (PCC) patient with uterine leiomyomas. Finally, two of the five variants were found to be pathogenic. A germline variant (c.817G>A, p.Ala273Thr) was found in a patient with a PPGL family history. A mosaic variant (c.206G>A, p.Gly69Asp) with an allelic ratio of 5% in blood DNA was confirmed in the PCC patient with uterine leiomyomas. No metastatic PPGL was observed in the two PPGL patients with FH pathogenic variants. In summary, we report mosaicism in FH and the first PPGL pedigree with an FH pathogenic germline variant. Both germline variants and mosaicism should be taken into account during genetic testing.

Case report: Two sisters with a germline CHEK2 variant and distinct endocrine neoplasias

Genetic testing has become the standard of care for many disease states. As a result, physicians treating patients who have tumors often rely on germline genetic testing results for making clinical decisions. Cases of two sisters carrying a germline CHEK2 variant are highlighted whereby possible other genetic drivers were discovered on tumor analysis. CHEK2 (also referred to as CHK2) loss of function has been firmly associated with breast cancer development. In this case report, two siblings with a germline CHEK2 mutation also had distinct endocrine tumors. Pituitary adenoma and pancreatic neuroendocrine tumor (PNET) was found in the first sibling and pheochromocytoma (PCC) discovered in the second sibling. Although pituitary adenomas, PNETs, and PCC have been associated with NF1 gene mutations, the second sister with a PCC did have proven germline CHEK2 with a pathogenic somatic NF1 mutation. We highlight the clinical point that unless the tumor is sequenced, the real driver mutation that is causing the patient's tumor may remain unknown.

Hypoxia signaling pathway: A central mediator in endocrine tumors

Adequate oxygen levels are essential for the functioning and maintenance of biological processes in virtually every cell, albeit based on specific need. Thus, any change in oxygen pressure leads to modulated activation of the hypoxia pathway, which affects numerous physiological and pathological processes, including hematopoiesis, inflammation, and tumor development. The Hypoxia Inducible Factors (HIFs) are essential transcription factors and the driving force of the hypoxia pathway; whereas, their inhibitors, HIF prolyl hydroxylase domain (PHDs) proteins are the true oxygen sensors that critically regulate this response. Recently, we and others have described the central role of the PHD/HIF axis in various compartments of the adrenal gland and its potential influence in associated tumors, including pheochromocytomas and paragangliomas. Here, we provide an overview of the most recent findings on the hypoxia signaling pathway in vivo, including its role in the endocrine system, especially in adrenal tumors.

Pheochromocytomas and paragangliomas in von Hippel-Lindau disease: not a needle in a haystack

OBJECTIVE

Pheochromocytomas are a hallmark feature of von Hippel-Lindau disease (vHL). To our knowledge, this is the first systematic review with meta-analysis evaluating the frequency of pheochromocytomas and/or paragangliomas (PPGLs) in patients with vHL, as well as among patients with different vHL subtypes.

DESIGN

Systematic review with meta-analysis.

METHODS

We searched on MEDLINE, Scopus, and Web of Science. We included primary studies assessing participants with vHL and reporting on the frequency of PPGL. We performed random-effects meta-analysis to quantitatively assess the frequency of PPGL, followed by meta-regression and subgroup analysis. Risk of bias analysis was performed to assess primary studies' methodological quality.

RESULTS

We included 80 primary studies. In 4263 patients with vHL, the pooled frequency of PPGL was 19.4% (95% CI = 15.9-23.6%, I2 = 86.1%). The frequency increased to 60.0% in patients with vHL type 2 (95% CI = 53.4-66.3%, I2 = 54.6%) and was determined to be of 58.2% in patients with vHL type 2A (95% CI = 49.7-66.3%, I2 = 36.2%), compared to 49.8% in vHL type 2B (95% CI = 39.9-59.7%, I2 = 42.7%), and 84.1% in vHL type 2C (95% CI = 75.1-93.1%, I2 = 0%). In meta-regression analysis, more recent studies were associated with a higher frequency of PPGL. All studies had at least one internal validity item classified as 'high risk of bias,' with 13% studies having low risk of bias in all external validity items.

CONCLUSIONS

PPGLs are a common manifestation of vHL. Despite methodological limitations and differences across primary studies, our results point to the importance of PPGL screening in patients with vHL.

Insights into Mechanisms of Pheochromocytomas and Paragangliomas Driven by Known or New Genetic Drivers

Simple Summary

Pheochromocytomas and paragangliomas are rare neuroendocrine tumors that are often hereditary. Although research has advanced considerably, significant gaps still persist in understanding risk factors, predicting metastatic potential and treating aggressive tumors. The study of rare mutations can provide new insights into how pheochromocytomas and paragangliomas develop. In this review, we provide examples of such rare events and how they can inform our understanding of the spectrum of mutations that can lead to these tumors and improve our ability to provide a genetic diagnosis.

Abstract

Pheochromocytomas and paragangliomas are rare tumors of neural crest origin. Their remarkable genetic diversity and high heritability have enabled discoveries of bona fide cancer driver genes with an impact on diagnosis and clinical management and have consistently shed light on new paradigms in cancer. In this review, we explore unique mechanisms of pheochromocytoma and paraganglioma initiation and management by drawing from recent examples involving rare mutations of hypoxia-related genes VHL, EPAS1 and SDHB, and of a poorly known susceptibility gene, TMEM127. These models expand our ability to predict variant pathogenicity, inform new functional domains, recognize environmental-gene connections, and highlight persistent therapeutic challenges for tumors with aggressive behavior.