Pheochromocytoma in von hippel-lindau disease: distinct histopathologic phenotype compared to pheochromocytoma in multiple endocrine neoplasia type 2

von Hippel-Lindau disease-related neoplasia with an emphasis on renal manifestations

von Hippel-Lindau (VHL) disease is characterized by biallelic inactivation of the VHL gene leading to abnormal or absent VHL protein function, and constitutive activation of hypoxia-inducible factors (HIF) that leads to pro-tumorigenic signaling. Individuals with VHL disease develop numerous cysts and tumors involving multiple organs including the kidneys, central nervous system, endolymphatic sac, lungs, pancreatobiliary system, adrenal glands, epididymis, and/or broad ligament. On histologic examination, these lesions show morphologic overlap as they are frequently characterized by cells with clear cytoplasm and prominent vascularity. In addition to distinguishing non-renal tumors from metastatic clear cell renal cell carcinoma, understanding site-specific histopathologic and immunophenotypic features of these tumors has several applications. This includes distinguishing VHL-related tumors from those that arise sporadically and lack VHL gene alterations, guiding further genetic workup, and helping distinguish between different genetic predisposition syndromes. In this context, immunohistochemical studies for markers such as paired box 8 (PAX-8), carbonic anhydrase 9 (CA9), and glucose transporter 1 (GLUT-1) have an important role in routine clinical practice and represent cost-effective diagnostic tools. The recent development of targeted therapeutics directed against HIF-mediated signaling represents a significant milestone in the management of VHL disease and highlights the importance of accurately diagnosing and characterizing the wide spectrum of VHL disease-associated lesions.

Neuropathologic features of central nervous system hemangioblastoma

Hemangioblastoma is a benign, highly vascularized neoplasm of the central nervous system (CNS). This tumor is associated with loss of function of the VHL gene and demonstrates frequent occurrence in von Hippel-Lindau (VHL) disease. While this entity is designated CNS World Health Organization grade 1, due to its predilection for the cerebellum, brainstem, and spinal cord, it is still an important cause of morbidity and mortality in affected patients. Recognition and accurate diagnosis of hemangioblastoma is essential for the practice of surgical neuropathology. Other CNS neoplasms, including several tumors associated with VHL disease, may present as histologic mimics, making diagnosis challenging. We outline key clinical and radiologic features, pathophysiology, treatment modalities, and prognostic information for hemangioblastoma, and provide a thorough review of the gross, microscopic, immunophenotypic, and molecular features used to guide diagnosis.

Clinical, Biochemical, Tumoural and Mutation Profile of VHL- and MEN2A-Associated Pheochromocytoma: A Comparative Study

OBJECTIVE

To compare clinical, biochemical, tumoural and mutational characteristics of Von Hippel Lindau Syndrome (VHL)-associated pheochromocytoma (PCC) to multiple endocrine neoplasia 2A (MEN2A)-associated pheochromocytoma.

DESIGN

Retrospective study design in a tertiary health care centre in Northern India.

METHODS

A total of 47 patients with biochemical and histologically proven pheochromocytoma/paraganglioma (PCC/PGL): 29 associated with VHL and 18 with MEN2A, were divided in two cohorts, respectively. Analysis of their medical records along with a prospective follow-up was done.

RESULTS

There were more children <19 years in VHL group (13 vs 1). Despite majority of VHL-PCC showing elevation of normetanephrine (NMN) (93%) as compared to MEN2A-PCC (22.2%), 75.8% presented with hypertension as compared to MEN2A (33.3%). The average size of VHL-PCC tumours was 5.66 cm. VHL-PCC as compared to MEN2A-PCC were multifocal (75% vs 61.1%), bilateral synchronous (72.4 vs 61.1%) and extra-adrenal (17.2% vs 0%). Both VHL (24%) and MEN2A-PCC (27.7%) showed multiple nodules, but more MEN2A PCC showed extra-tumoural hyperplasia (44.4% vs. 6.8%). In VHL, the commonest mutation (n = 17) was missense mutation with a hot spot on exon 3, while in MEN2A-PCC majority (66.6%) had 634 mutation in exon 11 and only 2 patients had the rare 611 mutation in exon 10.

CONCLUSION

In contrast to world literature, our study suggests Indian VHL-PCC can be symptomatic in spite of noradrenergic phenotype, large in size and multifocal. Multiple nodules in VHL-PCC could increase risk of recurrence following subtotal adrenalectomy.

Significance of Alpha-inhibin Expression in Pheochromocytomas and Paragangliomas

Alpha-inhibin expression has been reported in pheochromocytomas and paragangliomas (PPGLs). We analyzed alpha-inhibin immunohistochemistry in 77 PPGLs (37 pheochromocytomas [PCCs] and 40 paragangliomas) and correlated the results with catecholamine profile, tumor size, Ki-67 labeling index, succinate dehydrogenase B subunit and carbonic anhydrase IX (CAIX) staining, and genetic pathogenesis. PPGLs were classified as pseudohypoxic cluster 1 disease with documented VHL mutation or SDHx mutation or biochemical phenotype, whereas NF1-driven and RET-driven PPGLs and those with a mature secretory (adrenergic or mixed adrenergic and noradrenergic) phenotype were classified as cluster 2 disease. The Cancer Genome Atlas data on INHA expression in PPGLs was examined. Alpha-inhibin was positive in 43 PPGLs (56%). Ki-67 labeling indices were 8.07% and 4.43% in inhibin-positive and inhibin-negative PPGLs, respectively (P<0.05). Alpha-inhibin expression did not correlate with tumor size. Alpha-inhibin was expressed in 92% of SDHx-related and 86% of VHL-related PPGLs. CAIX membranous staining was found in 8 of 51 (16%) tumors, including 1 SDHx-related PCC and all 5 VHL-related PCCs. NF1-driven and RET-driven PPGLs were negative for alpha-inhibin and CAIX. Alpha-inhibin was expressed in 77% of PPGLs with a pseudohypoxia signature, and 20% of PPGLs without a pseudohypoxia signature (P<0.05). PPGLs with a mature secretory phenotype were negative for CAIX. The Cancer Genome Atlas data confirmed higher expression of INHA in cluster 1 than in cluster 2 PPGLs. This study identifies alpha-inhibin as a highly sensitive (90.3%) marker for SDHx/VHL-driven pseudohypoxic PPGLs. Although CAIX has low sensitivity, it is the most specific biomarker of VHL-related pathogenesis. While alpha-inhibin cannot replace succinate dehydrogenase B subunit immunohistochemistry for detection of SDHx-related disease, it adds value in prediction of cluster 1 disease. Importantly, these data emphasize that alpha-inhibin is not a specific marker of adrenal cortical differentiation, as it is also expressed in PCCs.

The North American Neuroendocrine Tumor Society Consensus Guidelines for Surveillance and Management of Metastatic and/or Unresectable Pheochromocytoma and Paraganglioma

ABSTRACT

This manuscript is the result of the North American Neuroendocrine Tumor Society consensus conference on the medical management and surveillance of metastatic and unresectable pheochromocytoma and paraganglioma held on October 2 and 3, 2019. The panelists consisted of endocrinologists, medical oncologists, surgeons, radiologists/nuclear medicine physicians, nephrologists, pathologists, and radiation oncologists. The panelists performed a literature review on a series of questions regarding the medical management of metastatic and unresectable pheochromocytoma and paraganglioma as well as questions regarding surveillance after resection. The panelists voted on controversial topics, and final recommendations were sent to all panel members for final approval.

Bilateral pheochromocytoma: Clinical characteristics, treatment and longitudinal follow-up

OBJECTIVE

Comprehensive data about patients with bilateral pheochromocytoma are limited. We aimed to describe the clinical presentation, genetic analysis, treatment and outcomes of patients with bilateral pheochromocytoma.

DESIGN

A retrospective study at a tertiary care centre.

PATIENTS

All patients with bilateral pheochromocytoma evaluated at Mayo Clinic in Rochester, Minnesota between January 1951 and December 2015.

MEASUREMENTS

Tumour size, genetic testing, plasma/urine metanephrines and catecholamines.

RESULTS

A total of 94 patients (51% women) were diagnosed with bilateral pheochromocytoma at a median age at first presentation of 31 years (range, 4-70). Bilateral disease was noted in 8.0% of pheochromocytoma patient overall and 37.5% of patients 18 years of younger. Most patients presented with synchronous tumours (80%). Median time to metachronous tumours was 4.5 years (range, 1-38). Genetic disease was identified in 75 (80%) patients, including MEN 2A (42.6%), VHL (19.1%), MEN 2B (9.6%) and NF1 (8.5%). Excess catecholamines were present in 97% of patients. Patients with synchronous pheochromocytoma commonly underwent simultaneous bilateral adrenalectomy (99%), and 18 (24%) had cortical-sparing surgery. Multicentric tumours were reported in 23 of 77 (30%) patients with available data. Recurrent disease was found in 9.6% of patients, and 8.5% developed metastatic disease. Median follow-up was 8.5 years. At the study conclusion, 4 patients had died due to pheochromocytoma or adrenalectomy.

CONCLUSIONS

Bilateral pheochromocytoma occurred in 7.0% of adults with pheochromocytoma and 37.5% of paediatric patients. Genetic disease was identified in 80% of patients, predominantly MEN2A. Multicentric tumours were common, but most were still cured following adrenalectomy.

Von Hippel-Lindau Disease: Current Challenges and Future Prospects

Understanding of molecular mechanisms of tumor growth has an increasing impact on the development of diagnostics and targeted therapy of human neoplasia. In this review, we summarize the current knowledge on molecular mechanisms and their clinical implications in von Hippel-Lindau (VHL) disease. This autosomal dominant tumor syndrome usually manifests in young adulthood and predisposes affected patients to the development of benign and malignant tumors of different organ systems mainly including the nervous system and internal organs. A consequent screening and timely preventive treatment of lesions are crucial for patients affected by VHL disease. Surgical indications and treatment have been evaluated and optimized over many years. In the last decade, pharmacological therapies have been evolving, but are largely still at an experimental stage. Effective pharmacological therapy as well as detection of biomarkers is based on the understanding of the molecular basis of disease. The molecular basis of von Hippel-Lindau disease is the loss of function of the VHL protein and subsequent accumulation of hypoxia-inducible factor with downstream effects on cellular metabolism and differentiation. Organs affected by VHL disease may develop frank tumors. More characteristically, however, they reveal multiple separate microscopic foci of neoplastic cell proliferation. The exact mechanisms of tumorigenesis in VHL disease are, however, still not entirely understood and knowledge on biomarkers and targeted therapy is scarce.

[Pathologist contribution in the diagnosis of hereditary predisposition to paranganglioma and pheochromocytoma]

Hereditary predispositions are responsible for more than 30% of or paraganglioma. Their identification is essential to optimize medical care and to offer an appropriate screening to relatives. To date, there are more than 15 known paraganglioma/pheochromocytoma predisposing genes. The most frequently involved are those encoding the succinate dehydrogenase (SDHx), accounting for half of cases and the VHL gene, causing the Von Hippel Lindau syndrome and representing approximately 20% of genetically determined cases. Patients with SDHB genes mutations have a higher risk of metastatic disease. An oncogenetic counseling is recommended to all patients developing one or several paragangliomas, isolated or associated with other tumors. Apart from the clinical presentation and in particular the syndromic forms characterized by specific tumor spectra, there is no validated morphological criterion allowing to suspect a hereditary form. On the other hand, pathologists have now access to several immunohistochemical tools allowing the identification of some hereditary forms, in particular those linked to the SDHx, VHL and FH genes. Thus, the loss of expression in immunohistochemistry of the SDHB or FH proteins orientates respectively, towards SDHx and FH genes, while the membrane expression of carbonic anhydrase IX (CA-IX) is a sensitive and specific tool pointing towards a VHL anomaly. Other immunohistochemical markers are under evaluation. A systematic SDHB immunohistochemical staining is recommended on all paragangliomas/pheochromocytomas in order to allow an early detection of the most common hereditary forms and to contribute to the interpretation of the genetic results in these patients seen in oncogenetics consultation.

An Update on the Histology of Pheochromocytomas: How Does it Relate to Genetics?

Pheochromocytomas are rare neuroendocrine tumors of the adrenal gland, whereas any extra-adrenal tumor with similar histology is designated as paraganglioma. These tumors have a very high rate of germline mutations in a large number of genes, up to 35% to 40%, frequently predisposing for other tumors as well. Therefore, they represent a phenomenal challenge for treating physicians. This review focuses on pheochromocytomas only, with special attention to gross and microscopic clues to the diagnosis of genetic syndromes, including the role of succinate dehydrogenase subunit A and subunit B immunohistochemistry as surrogate markers for genetic analysis in the field of succinate dehydrogenase subunit gene mutations.

Endocrine Manifestations of Von Hippel-Landau Disease

Von Hippel-Lindau (VHL) disease is an autosomal dominant disorder characterized by various endocrine, nonendocrine, benign, and malignant tumors in various organs. VHL tumor suppressor gene, located on short arm of chromosome 3 is responsible for this. Pheochromocytoma (PCC) is one of the important endocrine manifestations that needs to be ruled out in case of VHL suspicion. In this review, we summarize the endocrine manifestations of VHL disease and their management while giving case history of five such cases.

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.

Von Hippel-Lindau disease: a single gene, several hereditary tumors

The Von Hippel-Lindau (VHL) disease is an autosomal dominant disorder characterized by the predisposition for multiple tumors caused by germline mutations in the tumor suppressor gene VHL. This disease is associated with a high morbidity and mortality and presents a variable expression, with different phenotypes from family to family, affecting different organs during the lifetime. The main manifestations of VHL are hemangioblastomas of the central nervous system and retina, renal carcinomas and cysts, bilateral pheochromocytomas, cystic and solid tumors of the pancreas, cystadenomas of the epididymis, and endolymphatic sac tumors. The discovery of any of the syndrome components should raise suspicion of this disease and other stigmas must then be investigated. Due to the complexities associated with management of the various VHL manifestation, the diagnosis and the follow-up of this syndrome is a challenge in the clinical practice and a multidisciplinary approach is needed. The particular relevance to endocrinologists is the detection of pheochromocytomas in 35% and islet cell tumors in 17% of VHL patients, which can be associated with hypertension, hypoglycemia, cardiac arrhythmias, and carcinoid syndrome. The purpose of this review is to define the Von Hippel-Lindau syndrome addressing its clinical aspects and classification, the importance of genetic counseling and to propose a protocol for clinical follow-up.

Adrenal Tumors in Adults

Although most adrenal tumors are not diagnostic dilemmas, there are cases that are challenging. This may be due to the tissue provided, for example fragmented tissue received in the setting of morcellation, or it may be due to inherently challenging histology, such as in cases with equivocal features of malignancy. Additionally, much has been learned about the molecular alterations of adrenal tumors, especially pheochromocytomas. Many of these alterations represent germline mutations with significant clinical implications for patients and their families. The aim of this review is to provide an overview of the most common adrenal tumors in adults so that pathologists can tackle these interesting tumors.

A pathologist's view: molecular profiles for diagnosing pheochromocytomas and paragangliomas

Pheochromocytomas (PCC) and paragangliomas (PGL) are catecholamine (CA)-producing tumors classified into well (WD)-, moderately (MD)- or poorly differentiated (PD) types by the Grading of Adrenal Pheochromocytoma and Paraganglioma (GAPP). Seventy percent of PCCs/PGLs are WD type with 4% metastasis, the rest are MD with 60% and PD are with 88% metastasis. Thus, PCCs/PGLs can also be classified as low-grade (WD type), intermediate grade (MD type) and high-grade malignancies (PD types). MD/PD types are with 70% metastasis. Thus, PCCs/PGLs can also be classified as low-grade (WD type) and high-grade malignancies (MD/PD types) using GAPP. Hereditary PCCs/PGLs have been previously classified into cluster 1 or cluster 2 based on genetic mutations involved and types of catecholamine produced by the tumors. GAPP revealed that tumors in cluster 1 and cluster 2 correspond to MD type and WD type, respectively. Susceptible genes for high-grade malignancy (PD type) are currently unknown.

15 YEARS OF PARAGANGLIOMA: Pathology of pheochromocytoma and paraganglioma

Pathologists using their routine diagnostic tools can contribute both to the care of patients with pheochromocytoma/paraganglioma and to understanding the pathobiology of the tumors. They can document details of tissue organization and cytology that are accessible only by microscopy and can characterize admixtures of cell types that are morphologically distinct or show differential expression of immunohistochemical markers. Current roles and challenges for pathologists include differential diagnosis, identifying clues to the presence of hereditary disease, and effective communication of pathology information for clinical and research purposes. Future roles will increasingly involve risk stratification, identification of actionable targets for personalized therapies, and aiding the interpretation of molecular tests by helping characterize genetic variants of unknown significance. It remains to be determined to what extent the need for pathology input will be overshadowed by the availability of genetic testing and other molecular analyses at ever-decreasing cost, together with very effective clinical paradigms for risk stratification and patient care.

Spatiotemporal Heterogeneity Characterizes the Genetic Landscape of Pheochromocytoma and Defines Early Events in Tumorigenesis

PURPOSE

Pheochromocytoma and paraganglioma (PPGL) patients display heterogeneity in the clinical presentation and underlying genetic cause. The degree of inter- and intratumor genetic heterogeneity has not yet been defined.

EXPERIMENTAL DESIGN

In PPGLs from 94 patients, we analyzed LOH, copy-number variations, and mutation status of SDHA, SDHB, SDHC, SDHD, SDHAF2, VHL, EPAS1, NF1, RET, TMEM127, MAX, and HRAS using high-density SNP array and targeted deep sequencing, respectively. Genetic heterogeneity was determined through (i) bioinformatics analysis of individual samples that estimated absolute purity and ploidy from SNP array data and (ii) comparison of paired tumor samples that allowed reconstruction of phylogenetic trees.

RESULTS

Mutations were found in 61% of the tumors and correlated with specific patterns of somatic copy-number aberrations (SCNA) and degree of nontumoral cell admixture. Intratumor genetic heterogeneity was observed in 74 of 136 samples using absolute bioinformatics estimations and in 22 of 24 patients by comparison of paired samples. In addition, a low genetic concordance was observed between paired primary tumors and distant metastases. This allowed for reconstructing the life history of individual tumors, identifying somatic mutations as well as copy-number loss of 3p and 11p (VHL subgroup), 1p (Cluster 2), and 17q (NF1 subgroup) as early events in PPGL tumorigenesis.

CONCLUSIONS

Genomic landscapes of PPGL are specific to mutation subtype and characterized by genetic heterogeneity both within and between tumor lesions of the same patient.

Endocrine manifestations of von Hippel-Lindau disease

von Hippel-Lindau (VHL) disease is an autosomal dominant disorder caused by heterozygous mutations in the VHL tumor suppressor gene that is characterized by the occurrence of multiple endocrine and nonendocrine lesions. This review focuses on the endocrine manifestations of VHL disease. Pancreatic neuroendocrine proliferations (ductuloinsular complexes, islet dysplasia, endocrine microadenoma, and neuroendocrine tumors), pheochromocytomas, and extra-adrenal paragangliomas are important endocrine manifestations of VHL disease. They frequently display characteristic clinical, biochemical, and histopathologic features that, although not pathognomonic, can be helpful in suggesting VHL disease as the underlying etiology and distinguishing these tumors from sporadic cases. Recent improvements in treatment and outcomes of renal cell carcinomas have allowed pancreatic neuroendocrine tumors to emerge as a significant source of metastatic disease, making the accurate recognition and classification of these neoplasms by the pathologist of utmost importance to determine prognosis, treatment, and follow-up strategies for affected patients.

Nervous system involvement in von Hippel-Lindau disease: pathology and mechanisms

Patients with von Hippel-Lindau disease carry a germline mutation of the Von Hippel-Lindau (VHL) tumor-suppressor gene. We discuss the molecular consequences of loss of VHL gene function and their impact on the nervous system. Dysfunction of the VHL protein causes accumulation and activation of hypoxia inducible factor (HIF) which can be demonstrated in earliest stages of tumorigenesis and is followed by expression of VEGF, erythropoietin, nitric oxide synthase and glucose transporter 1 in VHL-deficient tumor cells. HIF-independent functions of VHL, epigenetic inactivation of VHL, pVHL proteostasis, and links between loss of VHL function and developmental arrest are also described. A most intriguing feature in VHL disease is the occurrence of primary hemangioblastic tumors in the nervous system, the origin of which has not yet been entirely clarified, and current hypotheses are discussed. Endolymphatic sac tumors may extend into the brain, but originally arise from proliferation of endolymphatic duct/sac epithelium; the exact nature of the proliferating epithelial cell, however, also has remained unclear, as well as the question why tumors almost consistently develop in the intraosseous portion of the endolymphatic sac/duct only. The epitheloid clear cell morphology of both advanced hemangioblastoma and renal clear cell carcinoma can make the differential diagnosis challenging, recent developments in immunohistochemical differentiation are discussed. Finally, metastasis to brain may not only be caused by renal carcinoma, but may derive from VHL disease-associated pheochromocytoma/paraganglioma, or pancreatic neuroendocrine tumor.

Long-term outcomes of surgical treatment for hereditary pheochromocytoma

BACKGROUND

The ideal surgical management of hereditary pheochromocytomas includes planning for a potential metachronous bilateral presentation and the possibility of lifelong steroid dependence if bilateral adrenalectomy is needed. An intact and viable cortical remnant after bilateral pheochromocytoma resection can eliminate the necessity for steroid dependency, but can increase the risk of pheochromocytoma recurrence.

STUDY DESIGN

We retrospectively reviewed outcomes of all patients with a diagnosis of hereditary pheochromocytomas treated at our tertiary cancer institution from 1962-2011, with subset analysis of patients undergoing a cortical-sparing procedure in the setting of bilateral adrenalectomy.

RESULTS

Of the ninety-six patients who underwent adrenalectomy for hereditary pheochromocytomas, 47 presented with bilateral disease. In 15 of the 49 patients (30%) who originally underwent unilateral adrenalectomy, pheochromocytoma developed in the contralateral gland at a median of 8.2 years (range 1 to 20 years) after the initial diagnosis. There were 4 recurrences in 55 cortical-sparing remnants (7%) and 3 recurrences in the adrenal bed after 101 intended total adrenal resections (3%) (p = 0.24). Total bilateral adrenalectomy was performed in 25 patients and acute adrenal insufficiency developed in 5 (20%) of those patients. An intended cortical-sparing adrenalectomy was performed in 39 patients and acute adrenal insufficiency developed in 1 (3%). Of these patients with adequate follow-up, 21 of 27 (78%) were steroid independent at 3-year follow-up. Sex, median age, adrenal vein preservation, metachronous adrenal resection, and bilateral cortical-sparing procedures did not predict steroid independence at 3 years.

CONCLUSIONS

Cortical-sparing adrenalectomy avoids long-term corticosteroid dependence in the majority of patients with hereditary pheochromocytoma with minimal risk of acute adrenal insufficiency. Recurrence occurs in approximately 7% of adrenal remnants.

Immunohistochemical markers of the hypoxic response can identify malignancy in phaeochromocytomas and paragangliomas and optimize the detection of tumours with VHL germline mutations

Background:

There are no reliable markers of malignancy in phaeochromocytomas (PCC) and paragangliomas (PGL). We investigated the relevance of the mammalian target of rapamycin (mTOR)/AKT and hypoxic pathways as novel immunohistochemical markers of malignancy.

Methods:

Tissue microarray blocks were constructed with a total of 100 tumours (10 metastatic) and 20 normal adrenomedullary samples. Sections were immunostained for hypoxia-inducible factor 1α (Hif-1α), vascular endothelial growth factor A (VEGF-A), mTOR, carbonic anhydrase IX (CaIX) and AKT. The predictive performance of these markers was studied using univariate, multivariate and receiver operating characteristic analyses.

Results:

In all, 100 consecutive patients, 64% PCC, 29% familial with a median tumour size of 4.7 cm (range 1–14) were included. Univariate analyses showed Hif-1α overexpression, tumour necrosis, size >5 cm, capsular and vascular invasion to be predictors of metastasis. In multivariate analysis, Hif-1α, necrosis and vascular invasion remained as independent predictors of metastasis. Hif-1α was the most discriminatory biomarker for the presence of metastatic diffusion. Strong membranous CaIX expression was seen in von Hippel–Lindau (VHL) PCC as opposed to other subtypes.

Conclusion:

Lack of vascular invasion, tumour necrosis and low Hif-1α expression identify tumours with lower risk of malignancy. We propose membranous CaIX expression as a potential marker for VHL disease in patients presenting with PCC.

Neuroendocrine tumors and tumor syndromes in childhood

Endocrine and neuroendocrine cells form a large and diverse array of cell types. They are present in the form of specialized organs, such as the pituitary, parathyroid, thyroid, and adrenal gland, or in the form of the diffuse neuroendocrine system in the respiratory and digestive tracts. Neuroendocrine tumors are a heterogeneous group of neoplasms, yet they present certain unifying features. These include frequent hormonal overproduction that leads to specific symptoms and a typical immunohistochemical staining profile with chromogranin A and synaptophysin reactivity. Over the past decades, many neuroendocrine tumors have been described in the context of heritable tumor syndromes, and there exist several syndromes that are almost entirely composed of neuroendocrine tumors. Tumors occurring as part of these hereditary syndromes are characterized by specific genetic abnormalities that have helped our understanding of tumorigenesis, and they frequently appear at a young age. It is therefore important for the pediatric pathologist to be aware of specific histologic characteristics of neuroendocrine tumors in childhood and of their association with specific tumor syndromes. This may alert other clinicians to the possibility of multiple tumors in the patient or his family members. This review focuses on hereditary syndromes with neuroendocrine tumors, including multiple endocrine neoplasia types 1 and 2, Von Hippel-Lindau disease, neurofibromatosis type 1, Carney complex, pheochromocytoma-paraganglioma syndrome, and familial nonmedullary thyroid carcinoma. In addition, several individual neuroendocrine tumors are described, such as medullary thyroid carcinoma, gastroenteropancreatic tumors, pheochromocytoma, and paraganglioma, emphasizing specific histopathologic characteristics.

Analysis of succinate dehydrogenase subunit B gene alterations in gastric cancers

Recently, the succinate dehydrogenase subunit B gene, SDHB, has emerged as a novel tumor suppressor. In this study, we have examined the genetic and epigenetic alterations of the SDHB gene in sporadic gastric adenocarcinomas in order to investigate if the SDHB gene is involved in gastric carcinogenesis. The expression of SDHB proteins was also examined with immunohistochemistry and Western blot in 184 and eight gastric cancers, respectively. There was loss or reduced expression of SDHB in 45 (24.5%) of the 184 gastric cancers. Statistically, altered expression of SDHB was not associated with clinicopathological parameters, including tumor differentiation, location, depth of invasion, and lymph node metastasis (P > 0.05). Western blot analysis showed a reduced expression of SDHB in four (50.0%) of the eight paired gastric cancer tissues. Genetic analysis showed one missense mutation, GCC --> ACC (Ala --> Thr) at codon 29. In addition, promoter hypermethylation was not detected in the gastric cancer samples. This is the first investigation of the genetic and protein expression analysis of the SDHB gene in gastric cancers. Our results suggest that genetic, epigenetic, and protein expression pattern alterations of the SDHB gene might play a minor role in the development or progression of gastric cancers.

A current review of the etiology, diagnosis, and treatment of pediatric pheochromocytoma and paraganglioma

CONTEXT

Pheochromocytomas and paragangliomas (PHEO/PGL) are neuroendocrine tumors that arise from sympathetic and parasympathetic paraganglia. Diagnosed rarely during childhood, PHEO/PGL are nonetheless important clinical entities, particularly given our evolving understanding of their pathophysiology.

EVIDENCE ACQUISITION

We identified articles through the U.S. National Library of Medicine by using the search terms pheochromocytoma and paraganglioma. Results were narrowed to manuscripts that included children and studies related to the genetics of PHEO/PGL. Web-based resources for genetic disorders were also used. For all articles, we performed subsequent reference searches and verification of source data.

EVIDENCE SYNTHESIS

Up to 20% of PHEO/PGL are diagnosed in children. Most are functional tumors, and clinical presentation includes symptoms related to catecholamine hypersecretion and/or tumor mass effect. Increasingly, PHEO/PGL are identified during presymptomatic screening in children with genetic syndromes associated with PHEO/PGL (multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and the paraganglioma syndromes). Plasma and/or urine metanephrines are the best diagnostic test for a functional tumor, and the management of pediatric patients is similar to adults. Genetic counseling should be undertaken in all cases. Although most pediatric PHEO/PGL are benign, these tumors can occasionally metastasize, a condition for which no curative treatment exists.

CONCLUSIONS

Although PHEO/PGL are rarely diagnosed during childhood, the pediatric provider should be able to recognize and screen for such tumors, particularly in the context of a known genetic predisposition. Optimal care of these children includes a multidisciplinary team approach at centers experienced in the evaluation and treatment of these uncommon yet fascinating endocrine neoplasms.

Histologic and immunohistochemical characterization of pheochromocytoma in 6 cotton-top tamarins (Saguinus oedipus)

Pheochromocytomas are uncommon neoplasms of the adrenal medulla that are most frequently reported in rats and select mouse strains. In many cases, especially those in man, pheochromocytoma is associated with familial tumor syndromes, because of inherited mutations in a variety of proto-oncogenes and tumor suppressor genes. Nonhuman primates are valuable animal models for a variety of human diseases because of their similar anatomy and physiology; however, cases of pheochromocytomas have only rarely been reported in nonhuman primates. Herein, we characterize the gross, histologic, and immunohistochemical features of pheochromocytoma in 6 cotton-top tamarins (Saguinus oedipus). Pheochromocytomas represented 6 of 114 of the total causes of death in the studied population (5.3%) and corresponded to 16% of the total number of neoplasms. The average age of affected animals was 17.9 years. On histologic examination, all cases were defined by tight bundles, nests, and cords of neoplastic chromaffin cells. All cases had concurrent myocardial degeneration and fibrosis of varying severity and chronicity. Three of the cases (50%) also had hyalinization and medial thickening of coronary arteries consistent with hypertension. On immunohistochemical examination, 6 of 6 of the cases (100%) stained positively for chromogranin A, synaptophysin, N-CAM (or CD56), and protein gene product 9.5. None of the cases stained for glial fibrillary acidic protein. Pedigree analysis revealed inter-relatedness in 4 of 6 animals, with progenitor animals also affected with pheochromocytomas. The tumors in this population illustrate comparable histologic and immunohistochemical staining patterns with cases in other laboratory animals and humans, and, therefore, may indicate common underlying genetic alterations that precipitate tumor development.

Pheochromocytoma and extra-adrenal paraganglioma: updates

CONTEXT

Advances in genetics and gene expression profiling have led to new ways of thinking about the pathobiology of pheochromocytoma and extra-adrenal paraganglioma. These developments are concurrent with the publication and dissemination of the 2004 World Health Organization bluebook on pathology and genetics of endocrine tumors.

OBJECTIVE

To summarize new information required by pathologists for effective participation in patient management and research.

DATA SOURCES

Literature review and primary material from Tufts Medical Center.

CONCLUSIONS

The World Health Organization reserves the term pheochromocytoma for tumors arising from chromaffin cells in the adrenal medulla. Closely related tumors in extra-adrenal sympathetic and parasympathetic paraganglia are classified as extra-adrenal paragangliomas. A pheochromocytoma is an intra-adrenal sympathetic paraganglioma. Although arbitrary, this nomenclature emphasizes important distinctive properties of intra-adrenal tumors, including an often adrenergic phenotype, relatively low rate of malignancy, and predilection to occur in particular hereditary syndromes. Malignancy is defined by presence of metastases not local invasion. Occult germline mutations characteristic of familial syndromes are now found in more than 20% of patients with apparently sporadic tumors, bringing the percentage of tumors with a known genetic basis close to 30%. In addition, tumor location and risk of malignancy vary with the underlying genetic defect. The "10 percent rule" for pheochromocytoma/paraganglioma--10% familial, 10% malignant, 10% extra-adrenal--is therefore no longer tenable. Current roles of pathology are limited to diagnosing primary or metastatic tumors and identifying features suggestive of malignant potential or hereditary disease. Future roles may involve more definitive assessment of malignancy, genotype-phenotype correlation, and identification of targets for therapy.

Mosaicism in von Hippel-Lindau disease: an event important to recognize

von Hippel-Lindau disease (VHL) is an autosomal dominant, familial neoplastic disorder with variable interfamilial and intrafamilial expression. VHL is characterized by pre-disposition to development of a combination of benign and malignant tumours affecting multiple organs. We provide molecular evidence of somatic mosaicism in nearly asymptomatic man whose daughter had VHL. The mosaic subject was found to have a cyst of the kidney and an angioma of the glans penis and had had surgery for a mandibular cyst and epididymal cystadenomas. Mosaicism could provide a genetic explanation for the clinical heterogeneity and variable severity of VHL. The real incidence of mosaicism is still unclear and the identification of mosaicism has important consequences in genetic counseling of VHL patients who appear to have de novo VHL mutations and should be considered when evaluating patients with isolated VHL-related tumours. Our results strongly suggest a complete and extensive clinical examination in the parents of each patient affected by an apparently de novo VHL germline mutation. We recommend performing a mutation screening of both parents of a proband with techniques that permit detection of low percentages of mosaicism before concluding that the proband has a de novo VHL mutation.

Neuropeptide Y expression in phaeochromocytomas: relative absence in tumours from patients with von Hippel-Lindau syndrome

Phaeochromocytomas are rare neuroendocrine tumours that produce catecholamines and numerous secretory proteins and peptides, including neuropeptide Y (NPY), a vasoactive peptide with influences on blood pressure. The production of catecholamines and NPY by phaeochromocytomas is highly variable. This study examined influences of hereditary factors and differences in catecholamine production on tumour expression of NPY, as assessed by quantitative PCR, enzyme immunoassay and immunohistochemistry. Phaeochromocytomas included hereditary adrenaline-producing tumours (adrenergic phenotype) in multiple endocrine neoplasia type 2 (MEN 2), predominantly noradrenaline-producing tumours (noradrenergic phenotype) in von Hippel-Lindau (VHL) syndrome, and other adrenergic and noradrenergic tumours where there was no clear hereditary syndrome. NPY levels in phaeochromocytomas from VHL patients were lower (P<0.0001) than in those from MEN 2 patients for both mRNA (84-fold difference) and the peptide (99-fold difference). These findings were supported by immunohistochemistry. NPY levels were also lower in VHL tumours than in those where there was no hereditary syndrome. Relative absence of expression of NPY in phaeochromocytomas from VHL patients when compared with other groups appears to be largely independent of differences in catecholamine production and is consistent with a unique phenotype in VHL syndrome.

Pheochromocytoma: recommendations for clinical practice from the First International Symposium. October 2005

The First International Symposium on Pheochromocytoma, held in October 2005, included discussions about developments concerning these rare catecholamine-producing tumors. Recommendations were made during the symposium for biochemical diagnosis, localization, genetics, and treatment. Measurement of plasma or urinary fractionated metanephrines, the most accurate screening approach, was recommended as the first-line test for diagnosis; reference intervals should favor sensitivity over specificity. Localization studies should only follow reasonable clinical evidence of a tumor. Preoperative pharmacologic blockade of circulatory responses to catecholamines is mandatory. Because approximately a quarter of tumors develop secondary to germ-line mutations in any one of five genes, mutation testing should be considered; however, it is not currently cost effective to test every gene in every patient. Consideration of tumor location, presence of multiple tumors, presence of metastases, and type of catecholamine produced is useful in deciding which genes to test. Inadequate methods to distinguish malignant from benign tumors and a lack of effective treatments for malignancy are important problems requiring further resolution.

Pathology of pheochromocytoma and extra-adrenal paraganglioma

The 2004 WHO classification of endocrine tumors defines pheochromocytoma as a tumor arising from chromaffin cells in the adrenal medulla. Closely related tumors in extra-adrenal sympathetic and parasympathetic paraganglia are classified as extra-adrenal paragangliomas. A pheochromocytoma is an intra-adrenal sympathetic paraganglioma. While arbitrary, this nomenclature serves to emphasize important distinctive properties of intra-adrenal tumors that must be taken into account in clinical practice and research. Those include an often adrenergic phenotype, a relatively low rate of malignancy, and a predilection to occur in particular hereditary syndromes. Current roles of pathology are limited to distinguishing primary or metastatic pheochromocytomas/paragangliomas from other endocrine or nonendocrine tumors, and flagging tumors that show features suggestive of malignant potential or syndromic disease. Future roles may involve more definitive assessment of malignancy, genotype-phenotype correlation, and identification of targets for therapy. Pathology practice currently rests mostly on interpretation of conventional histological sections stained with hematoxylin and eosin, with variable ancillary application of immunohistochemical staining. Malignancy is currently defined by the presence of metastases, not local invasion. Local invasion alone is a poor predictor of metastases, and the absence of apparent invasion does not preclude development of metastases. The two types of aggressive behavior might therefore have different biological underpinnings, and those will be resolved most effectively if consistent terminology is employed. In order to be optimally informative, pathology reports must employ consistent nomenclature and incorporate standard elements. Templates or checklists for minimal standard reporting are recommended by several pathology associations, but identification of some recommended and optional elements is currently subjective or inconsistent.

Histopathology and immunohistochemistry of adrenal medullary tumors and paragangliomas

Paragangliomas arise from sympathetic or parasympathetic paraganglia and should now be defined by their site and type. The term pheochromocytoma is reserved for intra-adrenal tumors. This short review discusses the gross and microscopic features, the immunohistochemical profile, the problem of recognizing malignant potential, and the rare instances where a differential diagnosis has to be considered.

Familial pheochromocytomas and paragangliomas: stories from the sign-out room

In this overview we present five patients with apparently sporadic pheochromocytomas or paragangliomas which turned out to be associated with an inheritable familial disease. For each patient a family history together with clinical, morphological, as well as molecular data are reported. The identified syndromes include multiple endocrine neoplasia type 2 (MEN2), von Hippel-Lindau syndrome (VHL), neurofibromatosis type 1 (NF1), and familial pheochromocytoma/paraganglioma syndrome (SDHx). A brief summary of phenotypes, the genes involved, and typical mutations in these syndromes is provided.

Molecular and cellular biology of pheochromocytomas and extra-adrenal paragangliomas

Efforts to understand the pathobiology of pheochromocytomas and extra-adrenal paragangliomas have been spurred by genetic and gene expression profiling studies showing genotype-phenotype correlations in familial pheochromocytoma/paraganglioma syndromes and in some sporadic tumors. The current challenge is to relate catalogs of genetic and phenotypic markers to cell biology. Hypothetical bases for genotype-phenotype correlations include: cell of origin, pathway dependence, and functional and anatomic context. A further consideration is phenotype plasticity. Cross talk between signaling pathways provides a general framework for understanding how mutations of apparently unrelated genes might lead to the same type of tumor, and also suggests that targeted therapies might be directed either at a specific mutated gene or a downstream signal transducer. However, precise mechanisms of tumorigenesis remain unknown. An intriguing hypothesis proposes that mutations of RET, NF1, VHL, or SDH predispose to hereditary pheochromocytoma/ paraganglioma by causing defective apoptotic culling of cells that would normally be destroyed during embryogenesis. An argument favoring survival rather than mitogenesis as a common denominator is that the same mutations are rare in sporadic pheochromocytomas/paragangliomas, suggesting they only need to act during a limited developmental window. An implication is that tumor precursors could be identified and eradicated in individuals who carry the mutations.

Hereditary hormone excess: genes, molecular pathways, and syndromes

Hereditary origin of a tumor helps toward early discovery of its mutated gene; for example, it supports the compilation of a DNA panel from index cases to identify that gene by finding mutations in it. The gene for a hereditary tumor may contribute also to common tumors. For some syndromes, such as hereditary paraganglioma, several genes can cause a similar syndrome. For other syndromes, such as multiple endocrine neoplasia 2, one gene supports variants of a syndrome. Onset usually begins earlier and in more locations with hereditary than sporadic tumors. Mono- or oligoclonal ("clonal") tumor usually implies a postnatal delay, albeit less delay than for sporadic tumor, to onset and potential for cancer. Hormone excess from a polyclonal tissue shows onset at birth and no benefit from subtotal ablation of the secreting organ. Genes can cause neoplasms through stepwise loss of function, gain of function, or combinations of these. Polyclonal hormonal excess reflects abnormal gene dosage or effect, such as activation or haploinsufficiency. Polyclonal hyperplasia can cause the main endpoint of clinical expression in some syndromes or can be a precursor to clonal progression in others. Gene discovery is usually the first step toward clarifying the molecule and pathway mutated in a syndrome. Most mutated pathways in hormone excess states are only partly understood. The bases for tissue specificity of hormone excess syndromes are usually uncertain. In a few syndromes, tissue selectivity arises from mutation in the open reading frame of a regulatory gene (CASR, TSHR) with selective expression driven by its promoter. Polyclonal excess of a hormone is usually from a defect in the sensor system for an extracellular ligand (e.g., calcium, glucose, TSH). The final connections of any of these polyclonal or clonal pathways to hormone secretion have not been identified. In many cases, monoclonal proliferation causes hormone excess, probably as a secondary consequence of accumulation of cells with coincidental hormone-secretory ability.

Pheochromocytoma and functional paraganglioma syndrome: no longer the 10% tumor

Pheochromocytomas and abdominal paragangliomas are catecholamine-producing tumors of the sympathetic nervous system, while head and neck paragangliomas are non-secreting tumors of parasympathetic origin. Recent developments in clinical and molecular research on these tumor forms have significantly clarified their genetic backgrounds and challenged the view of "pheochromocytoma as the 10% rule tumor." Firstly, a larger proportion of these tumors are today discovered in normotensive patients during imaging carried out for other reasons than suspicion of pheochromocytoma. Secondly, although the differential diagnosis between malignant and benign tumors remains a challenge, the risk of malignancy well exceeds the classical 10% in patients with extra-adrenal disease, and/or carriers of germ-line SDHB mutations. Finally, up to a third of patients carry a germ-line mutation in a gene predisposing to pheochromocytoma and/or paraganglioma. Identification of a constitutional mutation in RET, VHL, SDHD, or SDHB has implications for clinical screening and follow-up for both the patient and for relatives at risk who can be identified by screening for the same mutation. Genetic testing in apparently sporadic cases is therefore regarded as beneficial, especially in patients diagnosed before 50 years of age, and in patients with bilateral, multifocal, malignant and/or extra-adrenal disease.

Hypotension in a Woman with a Metastatic Dopamine-Secreting Carotid Body Tumor

OBJECTIVE

To describe a woman with metastatic carotid body tumor in whom hypotension occurred in the setting of exceedingly high plasma dopamine levels.

METHODS

We present a case report and review the literature on the topic of dopamine-secreting paraganglioma or pheochromocytoma.

RESULTS

A previously healthy 40-year-old Asian woman noted difficulty with swallowing and hoarseness. No neck mass was visible, and she had no symptoms of catecholamine excess and no family history of endocrine disorders or malignant disease. Indirect laryngoscopy revealed a paralyzed left vocal cord and a nonulcerating mass in the left parapharyngeal space. An initial needle biopsy was interpreted as undifferentiated carcinoma. After a second biopsy, this mass was diagnosed as a neuroendocrine tumor, consistent with paraganglioma. The patient underwent surgical resection and radiation therapy (total dose, 40 Gy), after which she remained asymptomatic for 11 years. Then loss of weight, fatigue, nausea, and hypotensive episodes (blood pressures as low as 70/35 mm Hg) prompted whole-body imaging with bone scans, computed tomography, and magnetic resonance imaging, which disclosed several lesions in the liver, lungs, and spine, suggestive of metastatic disease. The adrenal glands were unremarkable. A metaiodobenzylguanidine scan with use of (131)I was negative. Liver biopsy of a hypodense lesion revealed a neuroendocrine tumor by histologic and immunohistochemical studies. Because of the patient's history, malignant paraganglioma was diagnosed. The tumor secreted predominantly dopamine at extraordinary levels (plasma concentration 27,942 pg/mL; normal, <30). The patient died before further treatment could be initiated.

CONCLUSION

Carotid body tumors usually do not secrete catecholamines but frequently metastasize. During progression, these neuroendocrine tumors may become able to produce and secrete selected catecholamines such as dopamine. Dopamine can lower the blood pressure rather than causing hypertension, even though hypertension is one of the main symptoms of a pheochromocytoma.

[Tumors of the adrenal medulla and the paraganglia]

The sympathetic and parasympathetic paraganglia are the site of pheochromocytomas and paragangliomas. The adrenal pheochromocytoma and the abdominal paraganglioma derive from the sympathetic nervous system. The parasympathetic paragangliomas are predominantly localized in the head and neck region. Most pheochromocytomas are hormonally active and benign. The abdominal paragangliomas usually correspond to adrenal pheochromocytomas, but are more commonly malignant. The parasympathetic paragangliomas are usually benign, hormonally inactive and are most commonly located in the bifurcation of the carotid artery.

The molecular pathogenesis of hereditary and sporadic adrenocortical and adrenomedullary tumors

Modern imaging modalities lead to frequent detection of adrenal masses, most of them incidental findings. Although the majority of adrenocortical and adrenomedullary tumors are benign, there are no reliable clinical and laboratory markers to distinguish most of them from malignant neoplasms. The molecular mechanisms underlying the pathogenesis of these tumors have recently begun to be unraveled. A fruitful avenue for the elucidation of tumorigenesis has been the study of adrenal tumors that are manifestations of hereditary or postzygotic genetic syndromes, because one knows the "first hit", i.e. the primary gene defect. In contrast, in sporadic adrenal tumors the first hit, possibly a somatic mutation of a tumor-related gene, is unknown, and therefore the sequence of genetic alterations is difficult to establish. In this article we review in addition to our own work the literature on molecular aspects of adrenocortical and adrenomedullary tumorigenesis.

New insights into the genetics of familial chromaffin cell tumors

We review genetic aspects and recent advances in our understanding of the molecular pathogenesis of familial chromaffin cell tumors (pheochromocytoma, paraganglioma). About 10 percent of pheochromocytomas are familial and occur as part of multiple endocrine neoplasia type 2 (MEN 2), von Hippel-Lindau (VHL) disease, and neurofibromatosis type 1 (NF 1). A subset of paragangliomas, tumors that can also produce and secrete catecholamines, are also familial and occur in patients with germline mutations in genes that encode subunits of the mitochondrial complex II. The precise molecular mechanisms underlying the pathogenesis of chromaffin cell tumors remain widely unknown, although recent studies in hereditary tumors help elucidate their development. In MEN 2, overrepresentation of mutant RET in selected adrenomedullary cells may be an important mechanism in initiating the formation of a pheochromocytoma. In VHL disease, pheochromocytoma development appears to occur according to Knudson's two-hit model, a VHL germline mutation and wildtype allelic deletion. Tumorigenesis of NF1-associated pheochromocytomas remains unknown, as does tumor formation (i.e., carotid body tumor) in patients with germline mutations in SDHB, SDHC, and SDHD, genes that encode subunits of the mitochondrial complex II, the smallest complex in the respiratory chain. Many genetic alterations have been found in sporadic chromaffin cell tumors. However, at present such genetic changes are difficult to place into context with regard to tumor formation and progression.