Understanding catecholamine metabolism as a guide to the biochemical diagnosis of pheochromocytoma

A puzzling malignant adrenal tumor

A previously healthy 49-year-old male presented with abdominal pain, constitutional syndrome, paroxysmal palpitations and diaphoresis. Full-body CT scan showed a large malignant adrenal mass with abdominal lymph node and pulmonary metastasis. Biochemical studies revealed hypersecretion of catecholamines, cortisol, sexual steroids and steroid precursors; ACTH was not suppressed, and chromogranin A was negative. 18F-fluorodeoxyglucose PET/CT showed intense tracer uptake in the adrenal mass and abdominal lymph nodes. He was placed under adrenergic blockade and offered cytoreductive surgery, but his evolution was unfavorable with rapid clinical deterioration due to compressive abdominal symptoms, uncontrolled pain, peripheral oedema, cachexia and severe dilated cardiomyopathy. 123I-metaiodobenzylguanidine scintigraphy was negative. Poor clinical status precluded any surgical or systemic treatments. A biopsy of the adrenal mass suggested adrenocortical carcinoma. Two weeks later he developed recurrent level 3 non-insulin mediated hypoglycemias, with suppressed levels of insulin, C-peptide, IGF-1 and IGF-BP3. He responded poorly to palliative measures and died within a week, four months after the initial diagnosis. We present a puzzling case of an aggressive stage IV adrenal malignancy with bizarre secretory profile. Although we could not obtain a surgical specimen, combined available data suggested adrenocortical carcinoma. The pathophysiology is uncertain, and we explored exceedingly rare scenarios, including adrenocortical carcinoma masquerading as pseudo-pheochromocytoma; synchronous adrenocortical carcinoma and pheochromocytoma; adrenal mixed corticomedullary tumor; and ACTH-producing pheochromocytoma. The presence of ectopic ACTH-dependent hypercortisolism, discordant plasma and urinary metanephrine levels and IGF-2 mediated hypoglycemias were also quite perplexing. To our knowledge, this is the first report of a malignant adrenal tumor co-secreting steroid hormones with ACTH-dependent hypercortisolism, catecholamines and IGF-2. We faced obvious diagnostic and therapeutic challenges and encourage future studies to explore the complex interactions between cortical and chromaffin cells of the adrenal gland, that may have bidirectionally contributed to this patient's condition.

Phaeochromocytoma and paraganglioma

Phaeochromocytomas and paragangliomas are rare catecholamine-producing neuroendocrine tumours which can potentially cause catastrophic crises with high morbidity and mortality. This best practice article considers the causes and presentation of such tumours, screening and diagnostic tests, management of these patients and consideration of family members at risk.

A Rare Case of Metastatic Adrenal Melanoma

Metastatic melanoma presents a significant clinical challenge, characterized by its aggressive nature and propensity to spread to multiple organ systems. Despite advances in detection and treatment, managing metastatic disease remains complex. Here, we present the case of a 43-year-old male with metastatic melanoma displaying an unusual pattern of involvement, affecting the adrenal gland, liver, spleen, and bones. The diagnostic process was intricate, involving atypical hormonal profiles and a negative BRAF status, necessitating a comprehensive approach for accurate characterization and treatment selection. Immunotherapy demonstrated efficacy but also highlighted the emergence of immune-related adverse events, notably hyperglycemia. This case discusses the heterogeneous nature of metastatic melanoma and underscores the importance of a multidisciplinary approach, close monitoring, and consideration of evolving treatment strategies in its management.

[Comparison of the effectiveness of various methods for determining the level of metanephrines in the diagnosis of pheochromocytomas]

BACKGROUND

Pheochromocytoma (PHEO) is a tumor from the chromaffin tissue of the adrenal medulla, capable of hyperproduction of catecholamines. The increased production of hormones by the tumor leads to catecholamine crises, which have a pathological effect on all organs and systems. In the primary diagnosis of pheochromocytomas, it is important to determine the level of the metabolite of catecholamines - metanephrines. Currently, in clinical practice, various methods are used to determine the level of this metabolite: in blood plasma or in urine, total or only free form, fractionated analysis or unfractionated.

AIM

Comparison of the effectiveness of various methods for determining the level of metanephrines for the diagnosis of pheochromocytomas.

MATERIALS AND METHODS

A retrospective single-center cohort study was conducted on a sample of patients who were initially operated on for adrenal neoplasm at the Pirogov St. Petersburg State University High Medical Technology Clinic from November 2007 to December 2022 and who passed analysis to determine the level of blood or urine metanephrins before surgical treatment. The results of tests for metanephrine and tumor size were evaluated.

RESULTS

1088 patients with adrenal neoplasms who underwent surgical treatment were examined, of which 348 had histologically confirmed the presence of pheochromocytoma. Four types of metanephrine assays were compared: free fractionated plasma metanephrines (232 patients), unfractionated daily urine metanephrines (431 patients), fractionated total daily urine metanephrines (427 patients) and fractionated free daily urine metanephrines (178 patients). The greatest sensitivity was demonstrated by the analysis of free fractionated plasma methanephrines (95.4%). Unlike others, the sensitivity of this analysis did not decrease in the group of patients with small pheochromocytomas (3 cm or less). The greatest specificity was demonstrated by the analysis of unfractionated metanephrines in daily urine (97.8%), with the lowest sensitivity among all tests (67.6%). The study of fractionated total daily urine metanephrins showed good results of sensitivity and specificity, only slightly inferior to the best indicators, and the analysis of free daily urine metanephrins demonstrated unexpectedly low efficiency. There is a positive correlation between the level of metanephrine in the blood and the size of the tumor.

CONCLUSION

Based on the data obtained, the preferred assays for the primary diagnosis of pheochromocytoma can be considered the determination of fractionated free plasma metanephrines and fractionated total daily urine metanephrines, which is consistent with relevant clinical recommendations. It was found that the size of the tumor correlates with the severity of an increase in the level of metanephrins determined by any of the described methods.

An Update on Temporal Bone Paragangliomas

OPINION STATEMENT

Temporal bone paragangliomas (TBPs) are indolent, classically benign and highly vascular neoplasms of the temporal bone. There are two types of TBPs, tympanomastoid paragangliomas (TMPs) and tympanojugular paragangliomas (TJPs). The most common symptoms are hearing loss and pulsatile tinnitus. Diagnostic workup, besides conventional physical and laboratory examinations, includes biochemical testing of catecholamine and genetic testing of SDHx gene mutations as well as radiological examination. Although surgery is traditionally the mainstay of treatment, it is challenging due to the close proximity of tumor to critical neurovascular structures and thus the high risk of complications, especially in patients with advanced lesions. Radiotherapy and active surveillance have been increasingly recommended for selected patients. Decision on treatment should be made comprehensively. Curative effect depends on various factors. Long-term follow-up with clinical, laboratory, and radiological examinations is essential for all patients.

Biochemical Assessment of Pheochromocytoma and Paraganglioma

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances.

A Laboratory Medicine Perspective on the Investigation of Phaeochromocytoma and Paraganglioma

Phaeochromocytomas (PC) and sympathetic paragangliomas (PGL) are potentially malignant tumours arising from the adrenal medulla (PC) or elsewhere in the sympathetic nervous system (PGL). These tumours usually secrete catecholamines and are associated with significant morbidity and mortality, so accurate and timely diagnosis is essential. The initial diagnosis of phaeochromocytoma/paraganglioma (PPGL) is often dependent on biochemical testing. There is a range of pre-analytical, analytical and post-analytical factors influencing the analytical and diagnostic performance of biochemical tests for PPGL. Pre-analytical factors include patient preparation, sample handling and choice of test. Analytical factors include choice of methodology and the potential for analytical interference from medications and other compounds. Important factors in the post-analytical phase include provision of appropriate reference ranges, an understanding of the potential effects of various medications on metanephrine concentrations in urine and plasma and a consideration of PPGL prevalence in the patient population being tested. This article reviews these pre-analytical, analytical and post-analytical factors that must be understood in order to provide effective laboratory services for biochemical testing in the diagnosis of PPGL.

A Cortisol-Secreting Adrenal Adenoma Combined With a Micro-Pheochromocytoma: Case Report and Literature Review

Cushing's syndrome and pheochromocytomas (PCCs) are associated with endocrine hypertension. Cortisol-producing adrenal adenomas are a major cause of Cushing's syndrome. Simultaneous occurrence of cortisol-producing adrenal adenomas and PCCs is rare. Additionally, a PCC generally produces catecholamines in proportion to its size; therefore, micro-PCCs are rarely found in clinical practice. It is unknown whether micro-PCCs produce excess catecholamines during the pre-biochemical phase. Herein, we report the case of a 53-year-old woman who was referred to our hospital for further evaluation of left adrenal incidentaloma. She had been suffering from hypertension for 7 years. Endocrine tests indicated autonomous cortisol secretion, and she was diagnosed with cortisol-producing adrenal adenoma. A laparoscopic left adrenalectomy was performed. The final pathological examination revealed an adrenocortical adenoma measuring 26 × 24 mm. In addition, a micro-PCC measuring 3 × 2 mm was incidentally found near the cortisol-secreting adrenal adenoma in the ipsilateral adrenal gland. All catecholamine biosynthetic enzymes, tyrosine hydroxylase, aromatic l-amino acid decarboxylase, dopamine β-hydroxylase, and phenyl ethanolamine N-methyltransferase, were detected in this micro-PCC by immunohistochemical analyses. Although catecholamine levels were not biochemically elevated, the PCC expressed catecholamine biosynthetic enzymes. This is the first immunohistochemical report to show that a micro-PCC produces excess catecholamines in the pre-biochemical phase.

Tumour microenvironment in pheochromocytoma and paraganglioma

Pheochromocytomas and Paragangliomas (Pheo/PGL) are rare catecholamine-producing tumours derived from adrenal medulla or from the extra-adrenal paraganglia respectively. Around 10-15% of Pheo/PGL develop metastatic forms and have a poor prognosis with a 37% of mortality rate at 5 years. These tumours have a strong genetic determinism, and the presence of succinate dehydrogenase B (SDHB) mutations are highly associated with metastatic forms. To date, no effective treatment is present for metastatic forms. In addition to cancer cells, the tumour microenvironment (TME) is also composed of non-neoplastic cells and non-cellular components, which are essential for tumour initiation and progression in multiple cancers, including Pheo/PGL. This review, for the first time, provides an overview of the roles of TME cells such as cancer-associated fibroblasts (CAFs) and tumour-associated macrophages (TAMs) on Pheo/PGL growth and progression. Moreover, the functions of the non-cellular components of the TME, among which the most representatives are growth factors, extracellular vesicles and extracellular matrix (ECM) are explored. The importance of succinate as an oncometabolite is emerging and since Pheo/PGL SDH mutated accumulate high levels of succinate, the role of succinate and of its receptor (SUCNR1) in the modulation of the carcinogenesis process is also analysed. Further understanding of the mechanism behind the complicated effects of TME on Pheo/PGL growth and spread could suggest novel therapeutic targets for further clinical treatments.

Primary Functioning Hepatic Paraganglioma Treated by Laparoscopy: A Case Report

Paragangliomas are highly vascularised and often heritable tumors derived from the paraganglia. They are typically discovered in the retroperitoneal space as well as the head and neck region but are rarely encountered in the liver parenchyma. We report a case of a primary functioning hepatic paraganglioma and provide an up-to-date literature review of patients with such tumors. We present a case of functioning paraganglioma in a 34-year-old female patient who suffered a solitary lesion in her left lateral lobe with symptoms of hypertension since pregnancy. She did not have any family history and her pre-pregnancy examination was negative. An abdominal CT imaging revealed a 6.5 × 5.7 cm liver lesion in segments II and III. Laboratory investigations identified elevation in plasma-free catecholamines. With sufficient preoperative preparation, the patient underwent laparoscopic left hemihepatectomy. Immunohistochemical staining revealed Syn (+) tumor cell nests surrounded by S-100 sustentacular cells (+), providing a definitive diagnosis of paraganglioma. The patient recovered uneventfully without signs of recurrence during a 1-year follow-up period. Our case demonstrates that primary refractory hypertension in pregnancy should be screened for paraganglioma through abdominal ultrasound and plasma free catecholamines. On the other hand, laparoscopic surgery is technically safe and feasible for the treatment of patients with hepatic paragangliomas in favorable locations.

New Biology of Pheochromocytoma and Paraganglioma

Pheochromocytomas and paragangliomas continue to be defined by significant morbidity and mortality despite their several recent advances in diagnosis, localization, and management. These adverse outcomes are largely related to mass effect as well as catecholamine-induced hypertension, tachyarrhythmias and consequent target organ damage, acute coronary syndromes, and strokes (ischemic and hemorrhagic stroke). Thus, a proper understanding of the physiology and pathophysiology of these tumors and recent advances are essential to affording optimal care. These major developments largely include a redefinition of metastatic behavior, a novel clinical categorization of these tumors into 3 genetic clusters, and an enhanced understanding of catecholamine metabolism and consequent specific biochemical phenotypes. Current advances in imaging of these tumors are shifting the paradigm from poorly specific anatomical modalities to more precise characterization of these tumors using the advent and development of functional imaging modalities. Furthermore, recent advances have revealed new molecular events in these tumors that are linked to their genetic landscape and, therefore, provide new therapeutic platforms. A few of these prospective therapies translated into new clinical trials, especially for patients with metastatic or inoperable tumors. Finally, outcomes are ever-improving as patients are cared for at centers with cumulative experience and well-established multidisciplinary tumor boards. In parallel, these centers have supported national and international collaborative efforts and worldwide clinical trials. These concerted efforts have led to improved guidelines collaboratively developed by healthcare professionals with a growing expertise in these tumors and consequently improving detection, prevention, and identification of genetic susceptibility genes in these patients.

Drosophila HisT is a specific histamine transporter that contributes to histamine recycling in glia

Histamine is an important monoamine neurotransmitter that regulates multiple physiological activities in both vertebrates and invertebrates. Clearance and recycling of histamine are critical for sustaining histaminergic transmission. However, unlike other monoamine neurotransmitters, a histamine-specific transporter capable of clearing histamine from the synaptic cleft has not been identified. Here, through an in vitro histamine uptake screening, we identified an epithelial glia-expressing transporter, HisT (Histamine Transporter), that specifically transports histamine into cells. HisT misexpression in both pre- and postsynaptic neurons revealed a critical in vivo role for HisT in histamine transport and synaptic transmission. Last, we generated null hist alleles and demonstrated key physiological roles of HisT in maintaining histamine pools and sustaining visual transmission when the de novo synthesis of histamine synthesis was reduced. Our work identifies the first transporter that specifically recycles histamine and further indicates that the histamine clearance pathway may involve both the uptake-1 and uptake-2 transport systems.

Extraadrenal pheochromocytoma presenting with severe hematuria and postmicturition cephalgia, a case report of a rare bladder tumor entity

Paraganglioma (PGL) of the urinary bladder are a very rare tumor entity. Treatment of a PGL requires a multidisciplinary approach. We report on a case of a malignant pheochromocytoma (PHEO) of the bladder in a male adult due to a succinate dehydrogenase B (SDHB) subunit gene mutation where a partial cystectomy was perfomed after preoperative alpha blocking.

Dysfunction of calcium-regulated exocytosis at a single-cell level causes catecholamine hypersecretion in patients with pheochromocytoma

Neuroendocrine tumors constitute a heterogeneous group of tumors arising from hormone-secreting cells and are generally associated with a dysfunction of secretion. Pheochromocytoma (Pheo) is a neuroendocrine tumor that develops from chromaffin cells of the adrenal medulla, and is responsible for an excess of catecholamine secretion leading to severe clinical symptoms such as hypertension, elevated stroke risk and various cardiovascular complications. Surprisingly, while the hypersecretory activity of Pheo is well known to pathologists and clinicians, it has never been carefully explored at the cellular and molecular levels. In the present study, we have combined catecholamine secretion measurement by carbon fiber amperometry on human tumor cells directly cultured from freshly resected Pheos, with the analysis by mass spectrometry of the exocytotic proteins differentially expressed between the tumor and the matched adjacent non-tumor tissue. In most patients, catecholamine secretion recordings from single Pheo cells revealed a higher number of exocytic events per cell associated with faster kinetic parameters. Accordingly, we unravel significant tumor-associated modifications in the expression of key proteins involved in different steps of the calcium-regulated exocytic pathway. Altogether, our findings indicate that dysfunction of the calcium-regulated exocytosis at the level of individual Pheo cell is a cause of the tumor-associated hypersecretion of catecholamines.

Contemporary management of paragangliomas of the head and neck

Head and neck paragangliomas (HNPGLs) are rare neuroendocrine tumors typically arising from nonsecretory head and neck parasympathetic ganglia. Historically thought of as aggressive tumors that warranted equally aggressive surgical intervention, evidence has emerged demonstrating that the vast majority of HNPGLs are slow growing and indolent. It is also now recognized that a large proportion of HNPGLs are hereditary with succinate dehydrogenase gene mutations typically implicated. These recent advances have led to significant changes in the way in which clinicians investigate and treat HNPGLs with most now opting for more conservative treatment strategies. However, a proportion of patients present with more aggressive disease and still require nonconservative treatment strategies. Recent studies have sought to determine in which groups of patients the morbidity associated with treatment is justified. We summarize the recent advances in the understanding and management of these tumors and we provide our recommendations regarding the management of HNPGLs.

Accurate Location of Catheter Tip With the Free-to-Total Metanephrine Ratio During Adrenal Vein Sampling

BACKGROUND

The selectivity index (SI) of cortisol is used to document correct catheter placement during adrenal vein sampling (AVS) in patients with primary aldosteronism (PA). We aimed to determine the cutoff values of the SIs based on cortisol, free metanephrine, and the free-to-total metanephrine ratio (FTMR) using an adapted AVS protocol in combination with CT.

METHODS

Adults with PA and referred for AVS were recruited in two hypertension centers. The cortisol and free metanephrine-derived SIs were calculated as the concentration of the analyte in adrenal veins divided by the concentration of the analyte in the distal vena cava. The FTMR-derived SI was calculated as the concentration of free metanephrine in the adrenal vein divided by that of total metanephrine in the ipsilateral adrenal vein. The AVS was classified as an unequivocal radiological success (uAVS) if the tip of the catheter was seen in the adrenal vein. The SI cutoffs of each index marker were established using receiver operating characteristic curve analysis.

RESULTS

Out of 125 enrolled patients, 65 patients had an uAVS. The SI cutoffs were 2.6 for cortisol, 10.0 for free metanephrine, 0.31 for the FTMR on the left side, and 2.5, 9.9, and 0.25 on the right side. Compared to free metanephrine and the FTMR, cortisol misclassified AVS as unsuccessful in 36.6% and 39.0% of the cases, respectively.

CONCLUSION

This study is the first to calculate the SIs of cortisol, free metanephrine, and the FTMR indices for the AVS procedure. It confirms that free metanephrine-based SIs are better than those based on cortisol.

Low number of neurosecretory vesicles in neuroblastoma impairs massive catecholamine release and prevents hypertension

INTRODUCTION

Neuroblastoma (NB) is a pediatric cancer of the developing sympathetic nervous system. It produces and releases metanephrines, which are used as biomarkers for diagnosis in plasma and urine. However, plasma catecholamine concentrations remain generally normal in children with NB. Thus, unlike pheochromocytoma and paraganglioma (PHEO/PGL), two other non-epithelial neuroendocrine tumors, hypertension is not part of the usual clinical picture of patients with NB. This suggests that the mode of production and secretion of catecholamines and metanephrines in NB is different from that in PHEO/PGL, but little is known about these discrepancies. Here we aim to provide a detailed comparison of the biosynthesis, metabolism and storage of catecholamines and metanephrines between patients with NB and PHEO.

METHOD

Catecholamines and metanephrines were quantified in NB and PHEO/PGL patients from plasma and tumor tissues by ultra-high pressure liquid chromatography tandem mass spectrometry. Electron microscopy was used to quantify neurosecretory vesicles within cells derived from PHEO tumor biopsies, NB-PDX and NB cell lines. Chromaffin markers were detected by qPCR, IHC and/or immunoblotting.

RESULTS

Plasma levels of metanephrines were comparable between NB and PHEO patients, while catecholamines were 3.5-fold lower in NB vs PHEO affected individuals. However, we observed that intratumoral concentrations of metanephrines and catecholamines measured in NB were several orders of magnitude lower than in PHEO. Cellular and molecular analyses revealed that NB cell lines, primary cells dissociated from human tumor biopsies as well as cells from patient-derived xenograft tumors (NB-PDX) stored a very low amount of intracellular catecholamines, and contained only rare neurosecretory vesicles relative to PHEO cells. In addition, primary NB expressed reduced levels of numerous chromaffin markers, as compared to PHEO/PGL, except catechol O-methyltransferase and monoamine oxidase A. Furthermore, functional assays through induction of chromaffin differentiation of the IMR32 NB cell line with Bt2cAMP led to an increase of neurosecretory vesicles able to secrete catecholamines after KCl or nicotine stimulation.

CONCLUSION

The low amount of neurosecretory vesicles in NB cytoplasm prevents catecholamine storage and lead to their rapid transformation by catechol O-methyltransferase into metanephrines that diffuse in blood. Hence, in contrast to PHEO/PGL, catecholamines are not secreted massively in the blood, which explains why systemic hypertension is not observed in most patients with NB.

Adrenocortical Tumors and Pheochromocytoma/Paraganglioma Initially Mistaken as Neuroblastoma-Experiences From the GPOH-MET Registry

In children and adolescents, neuroblastoma (NBL), pheochromocytoma (PCC), and adrenocortical tumors (ACT) can arise from the adrenal gland. It may be difficult to distinguish between these three entities including associated extra-adrenal tumors (paraganglioma, PGL). Precise discrimination, however, is of crucial importance for management. Biopsy in ACT or PCC is potentially harmful and should be avoided whenever possible. We herein report data on 10 children and adolescents with ACT and five with PCC/PGL, previously mistaken as NBL. Two patients with adrenocortical carcinoma died due to disease progression. Two (2/9, missing data in one patient) patients with a final diagnosis of ACT clearly presented with obvious clinical signs and symptoms of steroid hormone excess, while seven patients did not. Blood analyses indicated increased levels of steroid hormones in one additional patient; however, urinary steroid metabolome analysis was not performed in any patient. Two (2/10) patients underwent tumor biopsy, and in two others tumor rupture occurred intraoperatively. In 6/10 patients, ACT diagnosis was only established by a reference pediatric pathology laboratory. Four (4/5) patients with a final diagnosis of PCC/PGL presented with clinical signs and symptoms of catecholamine excess. Urine tests indicated possible catecholamine excess in two patients, while no testing was carried out in three patients. Measurements of plasma metanephrines were not performed in any patient. None of the five patients with PCC/PGL received adrenergic blockers before surgery. In four patients, PCC/PGL diagnosis was established by a local pathologist, and in one patient diagnosis was revised to PGL by a pediatric reference pathologist. Genetic testing, performed in three out of five patients with PCC/PGL, indicated pathogenic variants of PCC/PGL susceptibility genes. The differential diagnosis of adrenal neoplasias and associated extra-adrenal tumors in children and adolescents may be challenging, necessitating interdisciplinary and multidisciplinary efforts. In ambiguous and/or hormonally inactive cases through comprehensive biochemical testing, microscopical complete tumor resection by an experienced surgeon is vital to preventing poor outcome in children and adolescents with ACT and/or PCC/PGL. Finally, specimens need to be assessed by an experienced pediatric pathologist to establish diagnosis.

Biochemical Diagnosis of Catecholamine-Producing Tumors of Childhood: Neuroblastoma, Pheochromocytoma and Paraganglioma

Catecholamine-producing tumors of childhood include most notably neuroblastoma, but also pheochromocytoma and paraganglioma (PPGL). Diagnosis of the former depends largely on biopsy-dependent histopathology, but this is contraindicated in PPGL where diagnosis depends crucially on biochemical tests of catecholamine excess. Such tests retain some importance in neuroblastoma though continue to largely rely on measurements of homovanillic acid (HVA) and vanillylmandelic acid (VMA), which are no longer recommended for PPGL. For PPGL, urinary or plasma metanephrines are the recommended most accurate tests. Addition of methoxytyramine to the plasma panel is particularly useful to identify dopamine-producing tumors and combined with normetanephrine also shows superior diagnostic performance over HVA and VMA for neuroblastoma. While use of metanephrines and methoxytyramine for diagnosis of PPGL in adults is established, there are numerous pitfalls for use of these tests in children. The establishment of pediatric reference intervals is particularly difficult and complicated by dynamic changes in metabolites during childhood, especially in infants for both plasma and urinary measurements, and extending to adolescence for urinary measurements. Interpretation of test results is further complicated in children by difficulties in following recommended preanalytical precautions. Due to this, the slow growing nature of PPGL and neglected consideration of the tumors in childhood the true pediatric prevalence of PPGL is likely underappreciated. Earlier identification of disease, as facilitated by surveillance programs, may uncover the true prevalence and improve therapeutic outcomes of childhood PPGL. For neuroblastoma there remain considerable obstacles in moving from entrenched to more accurate tests of catecholamine excess.

Dopamine-Secreting Pheochromocytoma and Paraganglioma

Predominantly or exclusively dopamine-secreting pheochromocytoma and paraganglioma are very rare. We report a 64-year-old woman with an adrenal incidentaloma. She was normotensive and had no symptoms of catecholamine excess. The 24-hour urine catecholamine level showed normal norepinephrine (122.9 μg/day), normal epinephrine (24.3 μg/day), and markedly elevated dopamine (148 212.4 μg/day). ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy revealed tumor uptake. After α-blockade as preoperative management, she successfully underwent laparoscopic left adrenalectomy and was finally diagnosed with an exclusively dopamine-secreting pheochromocytoma. The tumor was histologically comprised of small polygonal cells with high cellularity and was immunohistochemically positive for all 3 catecholamine-synthesizing enzymes: tyrosine hydroxylase (very weak), dopamine β-hydroxylase (heterogeneous), and phenylethanolamine N-methyltransferase (very weak). Electron microscopy revealed very few catecholamine-containing small vesicles with a few organelles, which reflected immature cells. No biochemical or imaging evidence of recurrence or metastasis were evident 1 year after the surgery. We conducted a literature search in the PubMed database. A total of 33 cases were collected. Our case had the second-highest 24-hour urinary dopamine excretion and was the first in which immunostaining for catecholamine synthase and electron microscopy were performed together. Histological findings in our case give a possible hypothesis that the mechanism underlying a dopamine-secreting pheochromocytoma is associated with immature catecholamine vesicles in which dopamine β-hydroxylase is localized, thus resulting in inhibited conversion from dopamine to norepinephrine. We also discuss the reasons for the lack of catecholamine excess symptoms, whether preoperative management of α-blockade is needed, and the association between the prognosis and genetic mutation, with an extensive literature review.

Quantitation of plasma metanephrines using isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS): a candidate reference measurement procedure and its application to evaluating routine ID-LC/MS/MS methods

Accurate measurement of plasma metanephrines (MNs) including metanephrine (MN) and normetanephrine (NMN) is crucial for the screening and diagnosis in pheochromocytomas and paragangliomas (PPGLs). Although the number of laboratories using liquid chromatography tandem mass spectrometry (LC-MS/MS) method to measure MNs has been increasing rapidly, those laboratory-developed assays showed incomparable results. There are no reference measurement procedures (RMPs) or reference materials (RMs) for MNs in Joint Committee for Traceability in Laboratory Medicine (JCTLM), which hindered the standardization of MNs measurement. We established a candidate RMP (cRMP) based on isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method for plasma MNs measurement. Plasma samples were spiked with MN-D3 and NMN-D3 as internal standards; protein precipitation and ion-exchange solid phase extraction (SPE) were performed to extract samples, eventually analyzed by LC-MS/MS. The cRMP was applied to evaluate two routine ID-LC/MS/MS methods through split-sample comparisons. Fifty-three individual patient samples were determined by cRMP and two routine ID-LC/MS/MS methods; results were analyzed by ordinary linear regression and Bland-Altman plots. The cRMP exhibited desirable imprecision, with intra-run and total imprecision (coefficient variation, CV) for MN being 0.79-1.36% and 1.53-1.87% and for NMN being 1.10-1.34% and 1.15-1.64%. The analytical recoveries of MN and NMN ranged from 98.3 to 101.7% and from 98.5 to 101.9%, respectively. Significant calibrator biases and sample-specific deviations were observed in method comparison. An accurate, precise, and reliable cRMP for plasma MNs was developed, and RMs with value assigned following the cRMP would help minimize the calibration bias and improve the comparability of different measuring systems.

Updated reference intervals for urine normetanephrine have no effect on test sensitivity but fewer false positives

OBJECTIVE

We previously highlighted the problem of frequent false positives in 24 h urine normetanephrine(UNM) measurements owing to reference intervals that are inappropriately low for the population being screened for pheochromocytoma. Using a large population database, we devised new age-stratified reference intervals for the 24 h UNM test that were higher compared to previous. However, it was uncertain as to whether this would compromise test sensitivity for true pheochromocytoma cases.

DESIGN AND METHODS

Retrospective analysis of all pheochromocytoma cases from a recently constructed provincial registry. All confirmed cases had their diagnostic UNM results retrospectively re-analysed according to the newly proposed UNM reference intervals to determine the percentage and phenotype of cases that might have been theoretically missed with the new reference range.

RESULTS

After excluding pediatric and non-secretory head and neck paragangliomas, there were 60 confirmed pheochromocytoma cases. Using prior reference intervals, 51/60 (85%) had an abnormally high UNM. Of the 9 with normal UNM, 4 had a high urine metanephrine(UMN), 5 had normal levels of both UNM and UMN such that 55/60 had abnormal test results, representing the historical combined test sensitivity of 92%. Using the proposed reference interval, 43/60 (72%) had high UNM results. Of the 17 with normal UNM, 12 had high UMN, 5 had normal levels of both UNM and UMN. Therefore, 55/60 patients had had elevations in either UNM or UMN, corresponding to an identical combined test sensitivity of 92%.

CONCLUSIONS

Reference intervals for UNM derived from actual clinical population screening data are higher than in traditional healthy volunteers. Use of these more appropriate reference intervals can significantly reduce the false positive rate without compromising test sensitivity for true pheochromocytoma.

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.

Adrenal pheochromocytoma with involvement of aorta and left renal artery: salvaged with adrenalectomy and nephrectomy

Large adrenal pheochromocytomas encasing the renal artery are a rare entity. The management of such challenging cases is surgical resection. The involvement of renal tissue and renal artery may necessitate meticulous dissection and concomitant nephrectomy. Here, we present a case of 41-year-old man diagnosed with left adrenal pheochromocytoma with complete encasement of left renal artery and partial encasement of aorta. Open left adrenalectomy and nephrectomy was performed after adequate preoperative optimisation. The patient is doing well at 6-month follow-up. Large adrenal pheochromocytoma with renal involvement is a rare presentation and requires optimal preoperative imaging, adequate preoperative alpha and beta blockade and meticulous surgical technique.

PET detectives: Molecular imaging for phaeochromocytomas and paragangliomas in the genomics era

Phaeochromocytomas and paragangliomas (PPGLs) are rare tumours that arise from the adrenal medulla or extra-adrenal sympathetic or parasympathetic paraganglia. Recent advances in genetics have greatly enhanced understanding of the pathogenesis and molecular physiology of PPGL. Concomitantly, advances in molecular imaging mean four techniques are now available for use in PPGLs: [¹²³ I]-MIBG coupled with SPECT/CT; [¹⁸ F]- FDG, [⁶⁸ Ga]-DOTATATE and [¹⁸ F]-FDOPA coupled with PET/CT. Each modality relies on unique cellular uptake mechanisms that are contingent upon the tumour's molecular behaviour-which, in turn, is determined by the tumour's genetic profile. This genotype-phenotype correlation means the appropriate choice of radiotracer may depend on the known (or suspected) underlying genetic mutation, in addition to the clinical indication for the scan-whether confirming diagnosis, staging disease, surveillance or determining eligibility for radionuclide therapy. Given these rapid recent changes in genetic understanding and molecular imaging options, many clinicians find it challenging to choose the most appropriate scan for an individual with PPGL. To this end, recent guidelines published by the European Association of Nuclear Medicine and the Society of Nuclear Medicine and Molecular Imaging (EANM/SNMMI) have detailed the preferred radiotracer choices for individuals with PPGL based on their genotype and/or clinical presentation, providing timely clarity in this rapidly moving field. The current review summarizes the implications of the genotype-phenotype relationship of PPGL, specifically relating this to the performance of molecular imaging modalities, to inform and enable practising endocrinologists to provide tailored, personalized care for individuals with PPGL.

Urinary Free Metanephrines for Diagnosis of Pheochromocytoma and Paraganglioma

BACKGROUND

Pheochromocytoma and paraganglioma (PPGL) is diagnosed through biochemical confirmation of excessive catecholamines in urine and plasma. Recent technological developments have allowed us to measure urinary free metanephrines; however, the diagnostic accuracy of these new methods and the diagnostic cutoff values have not been evaluated.

METHODS

This is a retrospective study of 595 subjects, including 71 PPGL cases and 524 controls. PPGL was based on pathological confirmation. Subjects with no evidence of PPGL over 2 years were included in the control group.

RESULTS

Urinary free metanephrines yielded similar area under the curve (AUC) to urinary fractionated metanephrines and plasma free metanephrines. However, urinary free normetanephrine yielded a better AUC than did urinary fractionated normetanephrine. The optimal cutoff for urinary free metanephrine and normetanephrine corrected for urinary creatinine yielded 97.2% sensitivity and 98.1% specificity.

CONCLUSION

Urinary free metanephrines are a reliable method for diagnosing PPGL in Asian populations compared with existing biochemical methods.

Urinary vanillylmandelic acid:creatinine ratio in dogs with pheochromocytoma

Pheochromocytoma diagnosis in dogs is challenging because biochemical tests are not always available. In humans, urinary vanillylmandelic acid (VMA) is part of a pheochromocytoma biochemical diagnostic profile, whereas its diagnostic accuracy is currently unknown in dogs with pheochromocytoma. Prospectively, VMA was determined by HPLC and expressed as the ratio with respect to urinary creatinine (VMA:C). The diagnostic accuracy of the VMA:C ratio was evaluated by analyzing the receiver operating characteristic (ROC) curve in 10 healthy dogs, 8 dogs with pituitary-dependent hypercortisolism, 8 dogs with adrenal-dependent hypercortisolism, and 7 dogs with pheochromocytoma. The pheochromocytoma diagnosis was confirmed by histology and immunohistochemistry in all tumors. The VMA:C ratio was significantly higher in dogs with pheochromocytoma (158 [53.4 to 230.8] × 10^-3) than in dogs with adrenal-dependent hypercortisolism (48.1 [24.3 to 144.9] × 10^-3; P < 0.05), dogs with pituitary-dependent hypercortisolism (37.5 [32 to 47.1] × 10^-3; P < 0.001), and healthy dogs (33.8 [13.3 to 87.9] × 10^-3; P < 0.001). When using a VMA:C ratio >58.2 × 10^-3 for pheochromocytoma diagnosis, a sensitivity of 85.7% and a specificity of 88.4% were obtained. Nevertheless, when using a cut-off ratio of 4 times the median VMA:C ratio determined in healthy dogs, there was no overlap (100% specificity). The area under the ROC curve indicated that the VMA:C ratio test could be used to discriminate between dogs with and without pheochromocytoma, what leads to the conclusion that it is useful for pheochromocytoma diagnosis in dogs.

The stress - Reproductive axis in fish: The involvement of functional neuroanatomical systems in the brain

The neuroendocrine-stress axis of nonmammalian species is evolutionarily conserved, which makes them useful to serve as important model systems for elucidating the function of the vertebrate stress response. The involvement of hypothalamo-pituitary-adrenal (HPA) axis hormones in regulation of stress and reproduction is well described in different vertebrates. However, the stress response is a complex process, which appears to be controlled by a number of neurochemicals in association with hypothalamo-pituitary-interrenal (HPI) axis or independent of HPI axis in fish. In recent years, the participation of neurohormones other than HPI axis in regulation of stress and reproduction is gaining more attention. This review mainly focuses on the involvement of functional neuroanatomical systems such as the catecholaminergic neurotransmitter dopamine (DA) and opioid peptides in regulation of the stress-reproductive axis in fish. Occurrences of DA and opioid peptides like β-endorphin, enkephalins, dynorphin, and endomorphins have been demonstrated in fish brain, and diverse roles such as pain modulation, social behaviour and reproduction are implicated for these hormones. Neuroanatomical studies using retrograde tracing, immunohistochemical staining and lesion methods have demonstrated that the neurons originating in the preoptic region and the nucleus lateralis tuberis directly innervate the pituitary gland and, therefore, the hypophysiotrophic role of these hormones. In addition, heightened synthetic and secretory activity of the opioidergic and the dopaminergic neurons in hypothalamic areas of the brain during stress exposure suggest potentially intricate relationship with the stress-reproductive axis in fish. Current evidence in early vertebrates like fish provides a novel insight into the underlying neuroendocrine mechanisms as additional pathways along the stress-reproductive axis that seem to be conserved during the course of evolution.

Detection of spot urinary free metanephrines and 3-methoxytyramine with internal reference correction for the diagnosis of pheochromocytomas and paragangliomas

Detection of normetanephrine (NMN), metanephrine (MN) and 3-methoxytyramine (3-MT) could be used to diagnose pheochromocytomas and paragangliomas (PPGLs). The accuracy for the diagnosis of PPGLs is only 6% by virtue of the classic symptom triad. In addition, false-positive results were found using plasma free MNs as biomarkers. Spot urinary free metanephrines (MNs) presented high specificity for PPGLs diagnosis in our previous work by HPLC with the electrochemical detection. Whereas, MNs and creatinine (Cr) need to be detected separately. A simple and specific method was urgently needed for the diagnosis of PPGLs. Here, we established a new HPLC method for spot urinary free MNs and 3-MT by the fluorescence detection and Cr by the ultraviolet detection simultaneously. It was worth mentioning that Cr for the virtue of being fairly constant in a given subject was used as an internal reference correction to eliminate the effect of spot urine volume for the diagnosis of PPGLs. Thirty-seven patients with PPGLs and 164 control subjects were detected by the established method and the peak area ratios of MNs and 3-MT to Cr were used innovatively for the diagnosis of PPGLs. The results showed acceptable precisions and recoveries. The sensitivities of the method were 94.6%, 91.9% and 86.5% and the specificities were 96.3%, 93.9% and 82.3%, respectively by the peak area of NMN/Cr, MN/Cr and 3-MT/Cr for the diagnosis. The established method provides a promising way for simple, rapid and accurate diagnosis of PPGLs.

Pediatric pheochromocytoma in association with Von Hippel-Lindau disease: Focus on screening strategies

INTRODUCTION

Von Hippel-Lindau disease (VHL) is a syndrome of familial predisposition to the development of malignant and benign tumours, due to mutations in the VHL tumour suppressor gene. Pheochromocytoma is a tumour that develops in the adrenal gland, rare in pediatric age, and may be associated with genetic abnormalities including mutations in the VHL gene. Systematic screening of pheochromocytoma in children carrying a VHL mutation has been proposed. However, some VHL patients who have been screened may develop symptoms associated with pheochromocytoma despite screening. Here, we report on such a case.

CLINICAL CASE

A 13-year-old boy, known to be a carrier of a mutation of the VHL gene, undergoing annual screening, was admitted to our hospital for clinical symptoms related to a right adrenal pheochromocytoma discovered on abdominal imaging. After hemodynamic stabilisation, the pheochromocytoma was surgically resected. Histology confirmed the diagnosis of pheochromocytoma. The postoperative care was simple. The event-free period is currently 2 years.

DISCUSSION

The present case has led us to reflect on the French and international screening strategies for pheochromocytoma in children carrying a mutation of the VHL gene. Between 2013 and 2018, six different recommendations were proposed for pheochromocytoma screening in secondary prevention for children with a VHL mutation, with variability regarding the age of onset and complementary examinations to be carried out. Despite the existence of these recommendations, our case demonstrates that a pheochromocytoma can develop by escaping well-performed screening. The role of early abdominal imaging should be redefined to improve the efficiency of screening.

CONCLUSION

The discovery of a pheochromocytoma in a child must be systematically investigated for an underlying genetic cause. In the particular case of children carrying a mutation of the VHL gene, annual abdominal imaging should be included in the pheochromocytoma screening protocol from the age of 5 years.

Plasma metanephrines and prospective prediction of tumor location, size and mutation type in patients with pheochromocytoma and paraganglioma

Objectives

Plasma free metanephrines are commonly used for diagnosis of pheochromocytoma and paraganglioma (PPGLs), but can also provide other information. This multicenter study prospectively examined whether tumor size, location, and mutations could be predicted by these metabolites.

Methods

Predictions of tumor location, size, and mutation type, based on measurements of plasma normetanephrine, metanephrine, and methoxytyramine were made without knowledge of disease in 267 patients subsequently determined to have PPGLs.

Results

Predictions of adrenal vs. extra-adrenal locations according to increased plasma concentrations of metanephrine and methoxytyramine were correct in 93 and 97% of the respective 136 and 33 patients in who these predictions were possible. Predicted mean tumor diameters correlated positively (p<0.0001) with measured diameters; predictions agreed well for pheochromocytomas but were overestimated for paragangliomas. Considering only patients with mutations, 51 of the 54 (94%) patients with NF1 or RET mutations were correctly predicted with those mutations according to increased plasma metanephrine, whereas no or minimal increase in metanephrine correctly predicted all 71 patients with either VHL or SDHx mutations; furthermore, among the latter group increases in methoxytyramine correctly predicted SDHx mutations in 93% of the 29 cases for this specific prediction.

Conclusions

Extents and patterns of increased plasma O-methylated catecholamine metabolites among patients with PPGLs allow predictions of tumor size, adrenal vs. extra-adrenal locations and general types of mutations. Predictions of tumor location are, however, only possible for patients with clearly increased plasma methoxytyramine or metanephrine. Where possible or clinically relevant the predictions are potentially useful for subsequent clinical decision-making.

An Adrenal Incidentaloma Diagnosed as Dopamine-Secreting Pheochromocytoma: A Case Report

BACKGROUND

Dopamine-secreting pheochromocytomas are exceedingly rare.

CASE PRESENTATION

A 28-year-old woman, who was admitted due to 4 hours of acute-onset abdominal pain, detected an adrenal mass incidentally. She was almost asymptomatic without a known family history. Laboratory assessments showed significant increases in dopamine levels of serum and 24-h urinary. By using preoperative a-adrenergic receptor blockers, she developed orthostatic hypotension and palpitations. When she underwent laparoscopic left adrenalectomy, she experienced rapid cyclic fluctuations in systolic blood pressure from 90 mmHg to 200 mmHg. Postoperatively, she exhibited prolonged hypotension, requiring vasopressor therapy and fluid replacement. According to histopathological diagnosis, it was a pheochromocytoma. Dopamine levels in 24-h urine and serum decreased to normal after operation. Analysis of specific gene SDHB, SDHD, RET, VHL and NF1 detected no pathogenic mutations.

CONCLUSION

Patients with dopamine-secreting pheochromocytomas are mostly asymptomatic, leading to a significant delay in diagnosis. There is a large possibility for dopamine-secreting pheochromocytomas to show a malignant tendency than the adrenergic and noradrenergic phenotypes. The a-adrenergic receptor blocker is not indicated for preoperative medical treatment because it can cause hypotension and cardiovascular failure. Calcium channel blockers or metyrosine may be better alternatives. All patients with pheochromocytomas should receive targeted genetic testing based on specific clinical features. SDHB, SDHD, RET, VHL and NF1 mutations are suggested for genetic testing of adrenal dopamine-secreting pheochromocytomas.

Pheochromocytoma and Paraganglioma: From Epidemiology to Clinical Findings

Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors. Pheochromocytomas arise from chromaffin cells in the adrenal medulla, and PGLs arise from chromaffin cells in the ganglia of the autonomic nervous system. Paragangliomas originate from sympathetic or parasympathetic ganglia in the abdomen, thorax, and pelvis. The majority of PCC and sympathetic PGL are endocrine active tumors causing clinical symptoms by secreting excess catecholamines (norepinephrine, epinephrine, dopamine) and their metabolites. The incidence of PCC and PGL ranges between 2 and 8 per million, with a prevalence between 1:2500 and 1:6500. It peaks between the 3rd and 5th decades of life, and approximately 20% of cases are pediatric patients. The prevalence among patients with hypertension in outpatient clinic ranges between 0.1-0.6% in adults and between 2-4.5% in the pediatric age group. 10-49% of these tumors is detected incidentally in imaging techniques performed for other reasons. However, 4-8% of adrenal incidentalomas are PCCs. Of these neuroendocrine tumors, 80-85% are PCCs and 15-20% are PGLs. Up to 40% of patients with PCC and PGL has disease-specific germline mutations and the situation is hereditary. Of 60% of the remaining sporadic patients, at least 1/3 has a somatic mutation in predisposing genes. 8% of the sporadic cases, 20-75% of the hereditary cases, 5% of the bilateral, adrenal cases, and 33% of the extra-adrenal cases at first presentation are metastatic. Although PCCs and PGLs have scoring systems for histological evaluation of the primary tumor, it is not possible to diagnose whether the tumor is malignant since there is no histological system approved for the biological aggressiveness of this tumor group. Metastasis is defined as the presence of chromaffin tissue in non-chromaffin organs, such as lymph nodes, liver, lungs and bone. Although most of the PCC and PGL are benign, the metastatic disease may develop in 15-17%. Metastatic disease is reported between 2-25% in PCCs and 2.4-60% in PGLs. The TNM staging system of the American Joint Committee on Cancer (AJCC) was developed to predict the prognosis, based on the specific anatomical features of the primary tumor and the occurrence of metastasis.

Update on Pheochromocytoma and Paraganglioma from the SSO Endocrine/Head and Neck Disease-Site Work Group. Part 1 of 2: Advances in Pathogenesis and Diagnosis of Pheochromocytoma and Paraganglioma

This first part of a two-part review of pheochromocytoma and paragangliomas (PPGLs) addresses clinical presentation, diagnosis, management, treatment, and outcomes. In this first part, the epidemiology, prevalence, genetic etiology, clinical presentation, and biochemical and radiologic workup are discussed. In particular, recent advances in the genetics underlying PPGLs and the recommendation for genetic testing of all patients with PPGL are emphasized. Finally, the newer imaging methods for evaluating of PPGLs are discussed and highlighted.

Pheochromocytoma: An approach to diagnosis

Pheochromocytomas are rare neuroendocrine chromaffin-derived tumors that arise within the adrenal medulla. They are usually benign, but if not diagnosed or if left untreated, they can have devastating consequences. Clinical consideration of the diagnosis is paramount, as they may have protean manifestations, and a high index of suspicion is essential if serious consequences are to be avoided. An accurate biochemical diagnosis is crucial for the management of these patients: either plasma or urinary metanephrines are both highly sensitive and specific if correctly employed, but knowledge of pre- and post-analytic interference is essential. Diagnostic imaging with cross-sectional CT and/or MRI offers high sensitivity in their detection, but lack specificity. The introduction of PET/CT/MR has led to a dramatic improvement in the localization of both pheochromocytomas and paragangliomas, together with the increasing availability of new functional imaging radionuclides. Optimal investigation and accurate diagnosis is best achieved at 'centers of excellence' with expert multidisciplinary teams.

Biochemical testing for neuroblastoma using plasma free 3-O-methyldopa, 3-methoxytyramine, and normetanephrine

BACKGROUND

Neuroblastoma, the most common extracranial solid tumor of childhood, produces catecholamines that are metabolized within tumor cells. Homovanillic acid (HVA) and vanillylmandelic acid (VMA), the end products of catecholamine metabolism, have limited accuracy for testing of the tumors. This study assessed whether metabolites produced in earlier steps of catecholamine metabolism might offer improved diagnostic accuracy over urinary HVA and VMA.

PROCEDURE

Plasma concentrations of 3-methoxytyramine, normetanephrine, and metanephrine were measured in two pediatric cohorts: (i) 96 children with confirmed neuroblastoma and (ii) 41 children with signs and symptoms of a catecholamine-producing tumor or other neoplasms and in whom neuroblastoma was excluded. Additional measurements of plasma 3-O-methyldopa and relationships of metabolites to MYCN amplification were examined in patient subgroups.

RESULTS

Overall, 94 of the 96 patients with neuroblastoma had concentrations of 3-methoxytyramine or normetanephrine above age-specific upper limits of reference intervals, providing a diagnostic sensitivity of 97.9% that was higher (P < 0.0001) than that of 82.2% for HVA and VMA. One of the two patients with normal plasma results showed an elevation of plasma 3-O-methyldopa. Diagnostic specificities were, respectively, 95.1% and 84.8%. Areas under receiver-operating characteristic curves confirmed the superior diagnostic power of the plasma than the urinary test (0.994 vs 0.945; P = 0.0095). Ratios of plasma 3-methoxytyramine to normetanephrine were 7.2-fold higher (P < 0.0001) for patients who had neuroblastomas with MYCN amplification than without MYCN amplification.

CONCLUSIONS

Measurements of plasma 3-methoxytyramine and normetanephrine provide a highly accurate diagnostic test for neuroblastoma and also offer potential for prognostic risk stratification.

Pheochromocytoma/paraganglioma: recent updates in genetics, biochemistry, immunohistochemistry, metabolomics, imaging and therapeutic options

Pheochromocytomas and paragangliomas (PPGLs), rare chromaffin/neural crest cell tumors, are commonly benign in their clinical presentation. However, there are a number of cases presenting as metastatic and their diagnosis and management becomes a dilemma because of their rarity. PPGLs are constantly evolving entities in the field of endocrinology brought about by endless research and discoveries, especially in genetics. Throughout the years, our knowledge and perception of these tumors and their genetic background has greatly expanded and changed, and each new discovery leads to advancement in the diagnosis, treatment and follow-up of PPGLs. In this review, we discuss the recent updates in the genetics, biochemistry, immunohistochemistry, metabolomics, imaging and treatment options of PPGLs.

Very high rate of false positive biochemical results when screening for pheochromocytoma in a large, undifferentiated population with variable indications for testing

OBJECTIVE

Pheochromocytoma/Paraganglioma (PPGL) is a rare tumor with non-specific presentations overlapping common entities like anxiety, hypertension, acute illness and episodic "spells." Assessment of urine normetanephrine or metanephrine (UNM-UMN) in real-life, where PPGL is very rare and PPGL mimics extremely common, may show overlap in results with loss of specificity depending on the reference range. We determined the extent to which UNM-UMN are high in people undergoing screening for PPGL.

DESIGN AND METHODS

Retrospective review of all UNM-UMN performed in a central lab serving Southern Alberta over 8 years.

RESULTS

After excluding pediatric ages and patients with CKD, there were 12,572 unique patients with 14,383 measures of UNM-UMN. 85 patients (0.7%) had markedly high UNM-UMN compatible with likely PPGL. Depending on the age category (in decades), 10-22% of all UNM results were above the upper reference limit(URL), particularly between ages of 40-60. Less than 3% had elevations in both UNM and UMN. Of those with high UNM, 99% were less than 3-fold the URL. Based on the population data, a potential new reference range for UNM is suggested, which may be more appropriate to the types of patient who undergo this form of testing.

CONCLUSIONS

There is an extraordinarily high prevalence of high UNM seen in real-life use of the test. However, the vast majority of high UNM are unlikely to be PPGL given the disease rarity and the massive number of tests ordered. This suggests the current laboratory URL may be too low (poor specificity) and/or the reference range may not be appropriate to the type of patient being screened for PPGL. Depending on the frequency of use of any screening test in a population, if the disease is rare and the specificity of the test is poor, a high rate of false positive results will be expected.

Pheochromocytomas and Paragangliomas

Pheochromocytomas are rare neuroendocrine tumors. Extra-adrenal lesions arising from the autonomic neural ganglia are termed paraganglioma. Clinical symptoms are common between the adrenal and extra-adrenal forms and are determined by excess secretion of catecholamines. Hypertension is a critical and often dramatic feature of pheochromocytoma/paraganglioma, and its most prevalent reported symptom. However, given the rare occurrence of this cancer, in patients undergoing screening for hypertension, the prevalence ranges from 0.1% to 0.6%. Still, patients frequently come to the attention of endocrinologist when pheochromocytoma/paraganglioma is suspected as a secondary cause of hypertension. This article summarizes current clinical approaches in patients with pheochromocytoma/paraganglioma.

Therapies targeting the signal pathways of pheochromocytoma and paraganglioma

Pheochromocytoma and paraganglioma (PCC/PGL) are rare tumors that originate from adrenal or extra-adrenal chromaffin cells. A significant clinical manifestation of PCC/PGL is that the tumors release a large number of catecholamines continuously or intermittently, causing persistent or paroxysmal hypertension and multiple organ functions and metabolic disorders. Though majority of the tumors are non-metastatic, about 10% are metastatic tumors. Others even have estimated that the rate of metastasis may be as high as 26%. The disease is most common in individuals ranging from 20 to 50 years old and the age of onset strongly depends on the genetic background: patients with germline mutations in susceptible genes have an earlier presentation. Besides, there are no significant differences in the incidence between men and women. At present, traditional treatments, such as surgical treatment, radionuclide therapy, and chemotherapy are still prior choices. However, they all have several deficiencies so that the effects are not extremely significant. Contemporary studies have shown that hypoxia-associated signal pathway, associated with the cluster 1 genes of PCC/PGL, and increased kinase signal pathways, associated with the cluster 2 genes of PCC/PGL, are the two major pathways involving the molecular pathogenesis of PCC/PGL, indicating that PCC/PGL can be treated with targeted therapies in emerging trends. This article reviews the progress of molecular-targeted therapies for PCC/PGL.

A high rate of modestly elevated plasma normetanephrine in a population referred for suspected PPGL when measured in a seated position

OBJECTIVE

Determine rate of high plasma normetanephrine or metanephrine (PNM-PMN) in a large sample of patients according to PNM-PMN posture and age-adjusted references.

DESIGN

Retrospective re-analysis of PNM-PMN from a Canadian reference laboratory (n = 5452), 2011-2015; most were in seated position (n = 5112) rather than supine (n = 340). An international PPGL database demonstrated expected distribution of supine PNM-PMN in PPGL patients.

METHODS

All PNM-PMN from a tertiary referral laboratory were reviewed. Any PNM-PMN result greater than 2× upper reference limit (URL) was considered likely true PPGL. Results 1-2× URL were uncertain, requiring additional testing/follow-up despite most being false positive given the rarity of PPGL. The rate of results in the 1-2× URL category were calculated for each group according to collection posture and differing published URL: seated, supine or supine age adjusted.

RESULTS

When collected and interpreted by seated URL, 19.6% of PNM required additional testing; only 4.6% being >2× URL. For patients over age 50 years, the abnormal rate was 24.9%. When collected supine, interpreted by supine age-adjusted URL, only 5.3% of PNM were mildly elevated. Possible false positives may be even lower when considering PMN or plasma methoxytyramine which were commonly high in true PPGL despite mild PNM elevations.

CONCLUSIONS

In a general medical population, seated PNM has a high rate of abnormal results, far exceeding expected prevalence. Supine measurement with supine, age-adjusted interpretation is strongly preferred prior to costly or invasive PPGL investigations.

SUMMARY

Review of 5452 plasma normetanephrine measurements showed 20% to be high, likely false positives for most. Supine, age-adjusted measures were half as likely to be elevated.

Intricacies of the Molecular Machinery of Catecholamine Biosynthesis and Secretion by Chromaffin Cells of the Normal Adrenal Medulla and in Pheochromocytoma and Paraganglioma

The adrenal medulla is composed predominantly of chromaffin cells producing and secreting the catecholamines dopamine, norepinephrine, and epinephrine. Catecholamine biosynthesis and secretion is a complex and tightly controlled physiologic process. The pathways involved have been extensively studied, and various elements of the underlying molecular machinery have been identified. In this review, we provide a detailed description of the route from stimulus to secretion of catecholamines by the normal adrenal chromaffin cell compared to chromaffin tumor cells in pheochromocytomas. Pheochromocytomas are adrenomedullary tumors that are characterized by uncontrolled synthesis and secretion of catecholamines. This uncontrolled secretion can be partly explained by perturbations of the molecular catecholamine secretory machinery in pheochromocytoma cells. Chromaffin cell tumors also include sympathetic paragangliomas originating in sympathetic ganglia. Pheochromocytomas and paragangliomas are usually locally confined tumors, but about 15% do metastasize to distant locations. Histopathological examination currently poorly predicts future biologic behavior, thus long term postoperative follow-up is required. Therefore, there is an unmet need for prognostic biomarkers. Clearer understanding of the cellular mechanisms involved in the secretory characteristics of pheochromocytomas and sympathetic paragangliomas may offer one approach for the discovery of novel prognostic biomarkers for improved therapeutic targeting and monitoring of treatment or disease progression.

A simple and robust liquid chromatography tandem mass spectrometry assay for determination of plasma free metanephrines and its application to routine clinical testing for diagnosis of pheochromocytoma

Plasma free metanephrines (PFMs) have high sensitivity for detecting pheochromocytoma (PCC). Herein, we developed a simple and reliable liquid chromatography tandem mass spectrometry assay for PFMs determination in Chinese population. PFMs were enriched by SPE without requiring extract evaporation or the use of buffers containing nonvolatile salts. The analytes were analyzed in multiple reaction monitoring mode. Inter- and intra-assay precisions were ≤4.3% and ≤ 6.3%. The lower limits of quantification were 0.07 nmol/L for metanephrine and 0.06 nmol/L for normetanephrine. Recoveries of PFMs were in the range of 89.3-113%. The method was free from significant matrix effect, carryover and interference. Owing to its fast analysis time, more than 150 samples/day could be easily performed by a single operator. With the established reference intervals of PFMs in the Chinese population, this simple and robust LC-MS/MS method could be valuable for use in routine clinical laboratories. It is noted that the combined tests of PFMs with urinary catecholamines or urinary vanillylmandelic acid could improve specificity.

The Catalytic Subunit β of PKA Affects Energy Balance and Catecholaminergic Activity

The protein kinase A (PKA) signaling system mediates the effects of numerous hormones, neurotransmitters, and other molecules to regulate metabolism, cardiac function, and more. PKA defects may lead to diverse phenotypes that largely depend on the unique expression profile of the affected subunit. Deletion of the Prkarcb gene, which codes for PKA catalytic subunit β (Cβ), protects against diet-induced obesity (DIO), yet the mechanism for this phenotype remains unclear. We hypothesized that metabolic rate would be increased in Cβ knockout (KO) mice, which could explain DIO resistance. Male, but not female, CβKO mice had increased energy expenditure, and female but not male CβKO mice had increased subcutaneous temperature and increased locomotor activity compared with wild-type (WT) littermates. Urinary norepinephrine (NE) and normetanephrine were elevated in female CβKO mice. CβKO mice had increased heart rate (HR); blocking central NE release normalized HR to that of untreated WT mice. Basal and stimulated PKA enzymatic activities were unchanged in adipose tissue and heart and varied in different brain regions, suggesting that Prkacb deletion may mediate signaling changes in specific brain nuclei and may be less important in the peripheral regulation of PKA expression and activity. This is a demonstration of a distinct effect of the PKA Cβ catalytic subunit on catecholamines and sympathetic nerve signaling. The data provide an unexpected explanation for the metabolic phenotype of CβKO mice. Finally, the sexual dimorphism is consistent with mouse models of other PKA subunits and adds to the importance of these findings regarding the PKA system in human metabolism.

Biochemical Diagnosis of Chromaffin Cell Tumors in Patients at High and Low Risk of Disease: Plasma versus Urinary Free or Deconjugated O-Methylated Catecholamine Metabolites

BACKGROUND

Measurements of plasma or urinary metanephrines are recommended for diagnosis of pheochromocytoma and paraganglioma (PPGL). What test offers optimal diagnostic accuracy for patients at high and low risk of disease, whether urinary free metanephrines offer advantages over deconjugated metanephrines, and what advantages are offered by including methoxytyramine in panels all remain unclear.

METHODS

A population of 2056 patients with suspected PPGLs underwent prospective screening for disease using mass spectrometric-based measurements of plasma free, urinary deconjugated, and urinary free metanephrines and methoxytyramine. PPGLs were confirmed in 236 patients and were excluded in others on follow-up evaluation.

RESULTS

Measurements of plasma free metabolites offered higher (P &lt; 0.01) diagnostic sensitivity (97.9%) than urinary free (93.4%) and deconjugated (92.9%) metabolites at identical specificities for plasma and urinary free metabolites (94.2%) but at a lower (P &lt; 0.005) specificity for deconjugated metabolites (92.1%). The addition of methoxytyramine offered little value for urinary panels but provided higher (P &lt; 0.005) diagnostic performance for plasma measurements than either urinary panel according to areas under ROC curves (0.991 vs 0.972 and 0.964). Diagnostic performance of urinary and plasma tests was similar for patients at low risk of disease, whereas plasma measurements were superior to both urinary panels for high-risk patients.

CONCLUSIONS

Diagnosis of PPGLs using plasma or urinary free metabolites provides advantages of fewer false-positive results compared with commonly measured deconjugated metabolites. The plasma panel offers better diagnostic performance than either urinary panel for patients at high risk of disease and, with appropriate preanalytics, provides the test of choice. Measurements of methoxytyramine in urine show limited diagnostic utility compared with plasma.

A Rare Coexistence of Pheochromocytoma and Parkinson's Disease With Diagnostic Challenges

We herein report a case of pheochromocytoma occurring in the course of Parkinson's disease. The coexistence of these two disease is extremely rare, with only four cases hitherto reported across the public databases. It is also noteworthy that biochemical tests, which are critical for the diagnosis of pheochromocytoma, are severely confounded by dopaminergic medications for Parkinson's disease, highlighting the importance of image-based modalities in this setting. We further attempted to gain insight into the potential molecular mechanisms, proposing that hypoxia-inducible factor signaling could make these two diseases mutually exclusive, while excessive reactive oxygen species could enable their coexistence.

A sensitive, high-throughput LC-MS/MS method for measuring catecholamines in low volume serum

A robust, sensitive, high-throughput method for the detection and quantification of catecholamines in serum, including dopamine, 5-methoxytryptamine, tyramine, phenylethylamine (PEA), epinephrine (EPI), norepinephrine (NE), metanephrine (MN), and normetanephrine (NMN) is described. It is based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a positive scheduled multiple reaction monitoring (MRM) mode. Key to the success of the method is the inclusion of an amine derivatization step, using phenylisothiocyanate (PITC), prior to liquid chromatographic separation of the targeted analytes on a C18 reversed-phase column. Mass spectrometric conditions, e.g., characteristic fragmentations and quantification transitions were also optimized to obtain maximum sensitivity and specificity. The limits of detection for all the target analytes are in the low nanomolar range. The recovery rates of spiked serum samples with three different concentration levels, i.e., low, medium, and high, are in the range of 93.2%-113% with satisfactory precision values of less than 10.9%. This method was successfully applied to determine the concentrations of dopamine, 5-methoxytryptamine, tyramine, PEA, EPI, NE, MN, and NMN in multiple human serum samples, with results matching closely those reported in the literature. Comparisons to other reported methods for measuring catecholamines indicates this new approach requires 10-20X less volume, making it ideal for targeted metabolomics studies with volume-limited samples. The method has been adapted to a 96-well plate format and has allowed the quantitative determination of catecholamines in more than 800 serum samples on a single instrument in just nine days.