Functional cardiac paraganglioma associated with a rare SDHC mutation

Recent progress in the pathologic classification of pheochromocytomas and paragangliomas

Pheochromocytomas and paragangliomas (PPGLs) represent a unique subset of neuroendocrine neoplasms (NENs) characterized by their genetic diversity and potential for catecholamine secretion. Similar to epithelial NENs, all PPGLs are classified as malignant neoplasms that are associated with a variable risk of metastatic spread. PPGLs arise from neuroendocrine cells of the adrenal medulla (intra-adrenal paraganglia) or extra-adrenal paraganglia. Advances over the past two decades have significantly enhanced our understanding of the biological and genetic underpinnings of these neoplasms, resulting in robust genotype-phenotype (e.g., morphology, anatomic distribution, catecholamine profile, biomarker profile, risk of metastasis) correlations that guide diagnosis and prognostication. The 2022 WHO classification of PPGLs emphasizes a shift away from morphology-only diagnostic approaches by ensuring the integration of morphology with functional, structural and pathogenesis-related biomarker studies into routine pathology practice when assessing PPGLs. This paradigm is critical in distinguishing metastatic disease from multifocal primary tumors, particularly in patients with germline mutations - a hallmark of PPGLs, with germline susceptibility observed in at least 40 % of cases. This review provides practicing pathologists with a concise update on modern diagnostic and risk assessment strategies for PPGLs, focusing on the integration of biomarkers, genetic profiling, and morphological features. It also addresses emerging challenges, such as identifying metastatic potential and distinguishing these from synchronous lesions, to improve multidisciplinary care of these patients.

Advanced imaging of cardiac Paraganglioma: A systematic review

Background and aims

Cardiac ParaGangliomas (PGLs) are rare extra-adrenal tumours that arise from chromaffin cells of the sympathetic ganglia. PGL are often diagnosed incidentally, with no symptoms or symptoms related to cardiovascular dysfunction.

Methods

Cardiac Computed Tomography (CCT) and Cardiac Magnetic Resonance (CMR) can detect the correct morphology and position of the lesion and provide proper tissue characterization.Nuclear medicine imaging, with Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) with specific radiotracers, can evaluate the functionality of the PGL and to distinguish a secreting from a non-secreting tumour.

Results

In association with biochemical parameters, a multimodal imaging approach, not yet standardized, can be useful both in the diagnosis, in the monitoring and in the treatment planning.

Conclusions

In this systematic review, we aim to investigate the role of diagnostic imaging, in particular CCT, CMR, PET and SPECT in diagnosis, characterization and monitoring of cardiac PGLs.

Diagnosis, Genetics, and Management of 24 Patients With Cardiac Paragangliomas: Experience From a Single Center

Context

Paragangliomas located within the pericardium represent a rare yet challenging clinical situation.

Objective

The current analysis aimed to describe the clinical characteristics of cardiac paragangliomas, with emphasis on the diagnostic approach, genetic background, and multidisciplinary management.

Methods

Twenty-four patients diagnosed with cardiac paraganglioma (PGL) in Peking Union Medical College Hospital, Beijing, China, between 2003 and 2021 were identified. Clinical data was collected from medical record. Genetic screening and succinate dehydrogenase subunit B immunohistochemistry were performed in 22 patients.

Results

The median age at diagnosis was 38 years (range 11-51 years), 8 patients (33%) were females, and 4 (17%) had familial history. Hypertension and/or symptoms related to catecholamine secretion were present in 22 (92%) patients. Excess levels of catecholamines and/or metanephrines were detected in 22 (96%) of the 23 patients who have completed biochemical testing. Cardiac PGLs were localized with 131I-metaiodobenzylguanidine scintigraphy in 11/22 (50%), and 99mTc-hydrazinonicotinyl-tyr3-octreotide scintigraphy in 24/24 (100%) patients. Genetic testing identified germline SDHx mutations in 13/22 (59%) patients, while immunohistochemistry revealed succinate dehydrogenase (SDH) deficiency in tumors from 17/22 (77%) patients. All patients were managed by a multidisciplinary team through medical preparation, surgery, and follow-up. Twenty-three patients received surgical treatment and perioperative death occurred in 2 cases. Overall, 21 patients were alive at follow-up (median 7.0 years, range 0.6-18 years). Local recurrence or metastasis developed in 3 patients, all of whom had SDH-deficient tumors.

Conclusion

Cardiac PGLs can be diagnosed based on clinical manifestations, biochemical tests, and appropriate imaging studies. Genetic screening, multidisciplinary approach, and long-term follow-up are crucial in the management of this disease.

Overview of the 2022 WHO Classification of Paragangliomas and Pheochromocytomas

This review summarizes the classification of tumors of the adrenal medulla and extra-adrenal paraganglia as outlined in the 5th series of the WHO Classification of Endocrine and Neuroendocrine Tumors. The non-epithelial neuroendocrine neoplasms (NENs) known as paragangliomas produce predominantly catecholamines and secrete them into the bloodstream like hormones, and they represent a group of NENs that have exceptionally high genetic predisposition. This classification discusses the embryologic derivation of the cells that give rise to these lesions and the historical evolution of the terminology used to classify their tumors; paragangliomas can be sympathetic or parasympathetic and the term pheochromocytoma is used specifically for intra-adrenal paragangliomas that represent the classical sympathetic form. In addition to the general neuroendocrine cell biomarkers INSM1, synaptophysin, and chromogranins, these tumors are typically negative for keratins and instead have highly specific biomarkers, including the GATA3 transcription factor and enzymes involved in catecholamine biosynthesis: tyrosine hydroxylase that converts L-tyrosine to L-DOPA as the rate-limiting step in catecholamine biosynthesis, dopamine beta-hydroxylase that is present in cells expressing norepinephrine, and phenylethanolamine N-methyltransferase, which converts norepinephrine to epinephrine and therefore can be used to distinguish tumors that make epinephrine. In addition to these important tools that can be used to confirm the diagnosis of a paraganglioma, new tools are recommended to determine genetic predisposition syndromes; in addition to the identification of precursor lesions, molecular immunohistochemistry can serve to identify associations with SDHx, VHL, FH, MAX, and MEN1 mutations, as well as pseudohypoxia-related pathogenesis. Paragangliomas have a well-formed network of sustentacular cells that express SOX10 and S100, but this is not a distinctive feature, as other epithelial NENs also have sustentacular cells. Indeed, it is the presence of such cells and the association with ganglion cells that led to a misinterpretation of several unusual lesions as paragangliomas; in the 2022 WHO classification, the tumor formerly known as cauda equina paraganglioma is now classified as cauda equina neuroendocrine tumor and the lesion known as gangliocytic paraganglioma has been renamed composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). Since the 4th edition of the WHO, paragangliomas have no longer been classified as benign and malignant, as any lesion can have metastatic potential and there are no clear-cut features that can predict metastatic behavior. Moreover, some tumors are lethal without metastatic spread, by nature of local invasion involving critical structures. Nevertheless, there are features that can be used to identify more aggressive lesions; the WHO does not endorse the various scoring systems that are reviewed but also does not discourage their use. The identification of metastases is also complex, particularly in patients with germline predisposition syndromes, since multiple lesions may represent multifocal primary tumors rather than metastatic spread; the identification of paragangliomas in unusual locations such as lung or liver is not diagnostic of metastasis, since these may be primary sites. The value of sustentacular cells and Ki67 labeling as prognostic features is also discussed in this new classification. A staging system for pheochromocytoma and extra-adrenal sympathetic PGLs, introduced in the 8th Edition AJCC Cancer Staging Manual, is now included. This paper also provides a summary of the criteria for the diagnosis of a composite paragangliomas and summarizes the classification of neuroblastic tumors. This review adopts a practical question-answer framework to provide members of the multidisciplinary endocrine oncology team with a most up-to-date approach to tumors of the adrenal medulla and extra-adrenal paraganglia.

Comprehensive review of evaluation and management of cardiac paragangliomas

Cardiac paraganglioma (PGL) is a rare neuroendocrine tumour causing significant morbidity primarily due to norepinephrine secretion potentially causing severe hypertension, palpitations, lethal tachyarrhythmias, stroke and syncope. Cardiologists are faced with two clinical scenarios. The first is the elevated norepinephrine, whose actions must be properly counteracted by adrenoceptor blockade to avoid catastrophic consequences. The second is to evaluate the precise location of a cardiac PGL and its spread since compression of cardiovascular structures may result in ischaemia, angina, non-noradrenergic-induced arrhythmia, cardiac dysfunction or failure. Thus, appropriate assessment of elevated norepinephrine by its metabolite normetanephrine is a gold biochemical standard at present. Furthermore, dedicated cardiac CT, MRI and transthoracic echocardiogram are necessary for the precise anatomic information of cardiac PGL. Moreover, a cardiologist needs to be aware of advanced functional imaging using ⁶⁸Ga-DOTA(0)-Tyr(3)-octreotide positron emission tomography/CT, which offers the best cardiac PGL-specific diagnostic accuracy and helps to stage and rule out metastasis, determining the next therapeutic strategies. Patients should also undergo genetic testing, especially for mutations in genes encoding succinate dehydrogenase enzyme subunits that are most commonly present as a genetic cause of these tumours. Curative surgical resection after appropriate α-adrenoceptor and β-adrenoceptor blockade in norepinephrine-secreting tumours is the primary therapeutic strategy. Therefore, appropriate and up-to-date knowledge about early diagnosis and management of cardiac PGLs is paramount for optimal outcomes in patients where a cardiologist is an essential team member of a multidisciplinary team in its management.

Clinical significance and peculiarities of succinate dehydrogenase B and hypoxia inducible factor 1α expression in parasympathetic versus sympathetic paragangliomas

BACKGROUND

Succinate dehydrogenase subunit B (SDHB) immunohistochemistry was considered a valuable tool to identify patients with inherited paraganglioma/pheochromocytoma (PGL/PCC). However, previous studies jointly analyzed 2 related but clinically distinct entities, parasympathetic head and neck paragangliomas (HNPGLs) and sympathetic PCCs/PGLs. Additionally, a role for hypoxia inducible factor-1α (HIF-1α) as a biomarker for succinate dehydrogenase (SDHx)-mutated tumors has not been studied. Here, we evaluated the utility of SDHB/HIF-1α proteins in HNPGLs and PCCs/PGLs as clinically useful biomarkers.

METHODS

The SDHB/succinate dehydrogenase subunit A (SDHA)/HIF-1α immunohistochemistry analysis was performed in 158 genetically defined patients.

RESULTS

Similarly to PCCs/PGLs, SDHB immune-negativity correlated with SDHx-mutations in HNPGLs (P < .0001). The HIF-1α stabilization was associated with SDHx-mutations in HNPGLs (P = .020), not in PCCs/PGLs (P = .319). However, 25% of SDHx-HNPGLs lacked HIF-1α positive cells.

CONCLUSION

As in PCCs/PGLs, SDHB immunohistochemistry in HNPGLs is a valuable method for identification of candidates for SDHx-genetic testing. On the contrary, although SDHx mutations may favor HIF-1α stabilization in HNPGLs, this is not a clinically useful biomarker.

The Diagnosis and Clinical Significance of Paragangliomas in Unusual Locations

Paragangliomas are neuroendocrine neoplasms, derived from paraganglia of the sympathetic and parasympathetic nervous systems. They are most commonly identified in the head and neck, being most frequent in the carotid body, followed by jugulotympanic paraganglia, vagal nerve and ganglion nodosum, as well as laryngeal paraganglia. Abdominal sites include the well-known urinary bladder tumors that originate in the Organ of Zuckerkandl. However, other unusual sites of origin include peri-adrenal, para-aortic, inter-aortocaval, and paracaval retroperitoneal sites, as well as tumors in organs where they may not be expected in the differential diagnosis of neuroendocrine neoplasms, such as thyroid, parathyroid, pituitary, gut, pancreas, liver, mesentery, lung, heart and mediastinum. The distinction of these lesions from epithelial neuroendocrine neoplasms is critical for several reasons. Firstly, the determination of clinical and biochemical features is different from that used for epithelial neuroendocrine tumors. Secondly, the genetic implications are different, since paragangliomas/pheochromocytomas have the highest rate of germline susceptibility at almost 40%. Finally, the characterization of metastatic disease is unique in these highly syndromic lesions. In this review, we summarize updated concepts by outlining the spectrum of anatomic locations of paragangliomas, the importance of morphology in establishing the correct diagnosis, the clinical implications for management, and the impact of genetics on the distinction between multifocal primary tumors compared with malignant disease.

Pathology and genetics of phaeochromocytoma and paraganglioma

Phaeochromocytoma and paraganglioma (PHEO/PGL) are rare tumours with an estimated annual incidence of 3 per million. Advances in molecular understanding have led to the recognition that at least 30-40% arise in the setting of hereditary disease. Germline mutations in the succinate dehydrogenase genes SDHA, SDHB, SDHC, SDHD and SDHAF2 are the most prevalent of the more than 19 hereditary genetic abnormalities which have been reported. It is therefore recommended that, depending on local resources and availability, at least some degree of genetic testing should be offered to all PHEO/PGL patients, including those with clinically sporadic disease. It is now accepted that that all PHEO/PGL have some metastatic potential; therefore, concepts of benign and malignant PHEO/PGL have no meaning and have been replaced by a risk stratification approach. Although there is broad acceptance that certain features, including high proliferative activity, invasive growth, increased cellularity, large tumour nests and comedonecrosis, are associated with an increased risk of metastasis, it remains difficult to predict the clinical behaviour of individual tumours and no single risk stratification scheme is endorsed or in widespread use. In this review, we provide an update on advances in the pathology and genetics of PHEO/PGL with an emphasis on the changes introduced in the WHO 2017 classification of endocrine neoplasia relevant to practising surgical pathologists.

PRECISION MEDICINE: AN UPDATE ON GENOTYPE/BIOCHEMICAL PHENOTYPE RELATIONSHIPS IN PHEOCHROMOCYTOMA/PARAGANGLIOMA PATIENTS

OBJECTIVE

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors known to produce and secrete high levels of circulating catecholamines and their metabolites. The biochemical characteristics of these tumors can be used to divide them into three major phenotypes. The adrenergic, noradrenergic and dopaminergic phenotypes are defined by predominant elevations in epinephrine and metanephrine, norepinephrine and normetanephrine, and dopamine and 3-methoxytyramine, respectively. There are over 15 well-identified tumor-susceptibility genes responsible for approximately 40% of the cases. The objective of this review article is to outline specific genotype/biochemical phenotype relationships.

METHODS

Literature review.

RESULTS

None.

CONCLUSION

Biochemical phenotype of PPGL is determined by the underlying genetic mutation and the associated molecular pathway. Identification of genotype/biochemical relationships is valuable in prioritizing testing for specific genes, making treatment decisions and monitoring disease progression.

ABBREVIATIONS

3-MT = 3-methoxytyramine; EPAS1 = endothelial pas domain protein 1; FH = fumarate hydratase; HIF2A = hypoxia inducible factor type 2A; MEN2 = multiple endocrine neoplasia type 2; NF1 = neurofibromatosis type 1; PNMT = phenylethanolamine N-methyltransferase; PPGL = pheochromocytoma and paraganglioma; RET = rearranged during transfection; SDH = succinate dehydrogenase; SDHAF2 = succinate dehydrogenase complex assembly factor 2; TCA = tricarboxylic acid; TH = tyrosine hydroxylase; TMEM127 = transmembrane protein 127; VHL = von Hippel-Lindau.

SDHB/SDHA immunohistochemistry in pheochromocytomas and paragangliomas: a multicenter interobserver variation analysis using virtual microscopy: a Multinational Study of the European Network for the Study of Adrenal Tumors (ENS@T)

Despite the established role of SDHB/SDHA immunohistochemistry as a valuable tool to identify patients at risk for familial succinate dehydrogenase-related pheochromocytoma/paraganglioma syndromes, the reproducibility of the assessment methods has not as yet been determined. The aim of this study was to investigate interobserver variability among seven expert endocrine pathologists using a web-based virtual microscopy approach in a large multicenter pheochromocytoma/paraganglioma cohort (n=351): (1) 73 SDH mutated, (2) 105 non-SDH mutated, (3) 128 samples without identified SDH-x mutations, and (4) 45 with incomplete SDH molecular genetic analysis. Substantial agreement among all the reviewers was observed either with a two-tiered classification (SDHB κ=0.7338; SDHA κ=0.6707) or a three-tiered classification approach (SDHB κ=0.6543; SDHA κ=0.7516). Consensus was achieved in 315 cases (89.74%) for SDHB immunohistochemistry and in 348 cases (99.15%) for SDHA immunohistochemistry. Among the concordant cases, 62 of 69 (~90%) SDHB-/C-/D-/AF2-mutated cases displayed SDHB immunonegativity and SDHA immunopositivity, 3 of 4 (75%) with SDHA mutations showed loss of SDHA/SDHB protein expression, whereas 98 of 105 (93%) non-SDH-x-mutated counterparts demonstrated retention of SDHA/SDHB protein expression. Two SDHD-mutated extra-adrenal paragangliomas were scored as SDHB immunopositive, whereas 9 of 128 (7%) tumors without identified SDH-x mutations, 6 of 37 (~16%) VHL-mutated, as well as 1 of 21 (~5%) NF1-mutated tumors were evaluated as SDHB immunonegative. Although 14 out of those 16 SDHB-immunonegative cases were nonmetastatic, an overall significant correlation between SDHB immunonegativity and malignancy was observed (P=0.00019). We conclude that SDHB/SDHA immunohistochemistry is a reliable tool to identify patients with SDH-x mutations with an additional value in the assessment of genetic variants of unknown significance. If SDH molecular genetic analysis fails to detect a mutation in SDHB-immunonegative tumor, SDHC promoter methylation and/or VHL/NF1 testing with the use of targeted next-generation sequencing is advisable.