Primary Pheochromocytomas Research Articles

Mutation of the Cell Cycle Regulator p27kip1 Drives Pseudohypoxic Pheochromocytoma Development.

Simple SummaryPheochromocytomas and paragangliomas (PPGLs) can be subdivided into at least three different subgroups associated with different clinical manifestations and depending on the risk to metastasize. A shortage in human tumor material, the lack of a functional human cell line and very limited animal models were major drawbacks for PPGL research and consequently for the development of patient-tailored targeted therapies. We have previously reported that the MENX rat model develops pheochromocytoma with a full penetrance at the age of 8–10 months, however, it was unclear which human group the rat tumors modeled best. In order to characterize the rat pheochromocytomas, we analyzed gene expression, the catecholamine profile, TCA-cycle metabolism, methylation, angiogenesis, histology and mitochondrial ultrastructure. In all aspects, rat MENX pheochromocytomas resemble the features of the human pseudohypoxia group, the most aggressive one and in need of effective therapeutic approaches.Background: Pseudohypoxic tumors activate pro-oncogenic pathways typically associated with severe hypoxia even when sufficient oxygen is present, leading to highly aggressive tumors. Prime examples are pseudohypoxic pheochromocytomas and paragangliomas (p-PPGLs), neuroendendocrine tumors currently lacking effective therapy. Previous attempts to generate mouse models for p-PPGLs all failed. Here, we describe that the rat MENX line, carrying a Cdkn1b (p27) frameshift-mutation, spontaneously develops pseudohypoxic pheochromocytoma (p-PCC). Methods: We compared rat p-PCCs with their cognate human tumors at different levels: histology, immunohistochemistry, catecholamine profiling, electron microscopy, transcriptome and metabolome. The vessel architecture and angiogenic potential of pheochromocytomas (PCCs) was analyzed by light-sheet fluorescence microscopy ex vivo and multi-spectral optoacoustic tomography (MSOT) in vivo. Results: The analysis of tissues at various stages, from hyperplasia to advanced grades, allowed us to correlate tumor characteristics with progression. Pathological changes affecting the mitochrondrial ultrastructure where present already in hyperplasias. Rat PCCs secreted high levels of norepinephrine and dopamine. Transcriptomic and metabolomic analysis revealed changes in oxidative phosphorylation that aggravated over time, leading to an accumulation of the oncometabolite 2-hydroxyglutarate, and to hypermethylation, evident by the loss of the epigenetic mark 5-hmC. While rat PCC xenografts showed high oxygenation, induced by massive neoangiogenesis, rat primary PCC transcriptomes possessed a pseudohypoxic signature of high Hif2a, Vegfa, and low Pnmt expression, thereby clustering with human p-PPGL. Conclusion: Endogenous rat PCCs recapitulate key phenotypic features of human p-PPGLs. Thus, MENX rats emerge as the best available animal model of these aggressive tumors. Our study provides evidence of a link between cell cycle dysregulation and pseudohypoxia.

Retrospective evaluation of toceranib phosphate (Palladia\xae) use in the treatment of inoperable, metastatic, or recurrent canine pheochromocytomas: 5 dogs (2014\u20132017)

BackgroundEffective treatment options for inoperable, metastatic, or recurrent canine pheochromocytomas are lacking. In humans, specific germline mutations exist that drive the development of pheochromocytomas. Pharmaceutical blockade of these abnormalities with small molecule inhibitors are an effective treatment strategy. Similar mutations may exist in the dog, and thus, treatment with similar small molecule inhibitors may provide a survival advantage. The purpose of this study was to assess the role of toceranib phosphate in the treatment of inoperable, metastatic, or recurrent canine pheochromocytomas.ResultsRetrospectively, medical records of dogs that had a diagnosis or suspect diagnosis of a pheochromocytoma were reviewed for information regarding response to toceranib phosphate and overall outcome. Five dogs were identified that fit the inclusion criteria. All five experienced clinical benefit (1 partial response, 4 stable disease). Progression-free interval (PFI) for the dog with the partial response was 61 weeks. PFI for the two dogs with stable measurable disease were 36 weeks and 28 weeks. PFI in the two dogs with stable metastatic disease were at least 11 weeks and 18 weeks.ConclusionsBased on this limited series of dogs, the results suggest that toceranib may have biological activity in dogs with primary and metastatic pheochromocytomas. Larger studies are needed to define the use and response to toceranib in dogs with gross, microscopic, and metastatic pheochromocytoma.

TERT structural rearrangements in metastatic pheochromocytomas.

Pheochromocytomas (PC) and paragangliomas (PGL) are endocrine tumors for which the genetic and clinicopathological features of metastatic progression remain incompletely understood. As a result, the risk of metastasis from a primary tumor cannot be predicted. Early diagnosis of individuals at high risk of developing metastases is clinically important and the identification of new biomarkers that are predictive of metastatic potential is of high value. Activation of TERT has been associated with a number of malignant tumors, including PC/PGL. However, the mechanism of TERT activation in the majority of PC/PGL remains unclear. As TERT promoter mutations occur rarely in PC/PGL, we hypothesized that other mechanisms - such as structural variations - may underlie TERT activation in these tumors. From 35 PC and four PGL, we identified three primary PCs that developed metastases with elevated TERT expression, each of which lacked TERT promoter mutations and promoter DNA methylation. Using whole genome sequencing, we identified somatic structural alterations proximal to the TERT locus in two of these tumors. In both tumors, the genomic rearrangements led to the positioning of super-enhancers proximal to the TERT promoter, that are likely responsible for the activation of the normally tightly repressed TERT expression in chromaffin cells.

N-Glycomic Profiling of Pheochromocytomas and Paragangliomas Separates Metastatic and Nonmetastatic Disease.

No effective methods for separating primary pheochromocytomas and paragangliomas with metastatic potential are currently available. The identification of specific asparagine-linked glycan (N-glycan) structures, which are associated with metastasized pheochromocytomas and paragangliomas, may serve as a diagnostic tool. To identify differences in N-glycomic profiles of primary metastasized and nonmetastasized pheochromocytomas and paragangliomas. This study was conducted at Helsinki University Hospital, University of Helsinki, and Glykos Finland Ltd. and included 16 pheochromocytomas and paragangliomas: 8 primary metastasized pheochromocytomas or paragangliomas and 8 nonmetastasized tumors. N-glycan structures were analyzed with matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) profiling of formalin-fixed, paraffin-embedded tissue samples. N-glycan profile of tumor tissue. Four groups of neutral N-glycan signals were more abundant in metastasized tumors than in nonmetastasized tumors: complex-type N-glycan signals of cancer-associated terminal N-acetylglucosamine, multifucosylated glycans (complex fucosylation), hybrid-type N-glycans, and fucosylated pauci-mannose-type N-glycans. Three groups of acidic N-glycans were more abundant in metastasized tumors: multifucosylated glycans, acid ester-modified (sulfated or phosphorylated) glycans, and hybrid-type/monoantennary N-glycans. Fucosylation and complex fucosylation were significantly more abundant in metastasized paragangliomas and pheochromocytomas than in nonmetastasized tumors for individual tests but were over the false positivity critical rate, when adjusted for multiplicity testing. MALDI-TOF MS profiling of primary pheochromocytomas and paragangliomas can identify diseases with metastatic potential based on their different N-glycan profiles. Thus, malignancy-linked N-glycan structures may serve as potential diagnostic tools for pheochromocytomas and paragangliomas.

HuR in pheochromocytomas and paragangliomas - overexpression in verified malignant tumors.

Pheochromocytomas and paragangliomas are rare, neural crest-originating, neuroendocrine tumors. HuR is an mRNA-binding protein of the ELAV/Hu-protein family, which participates in posttranscriptional regulation of many cancer-associated genes. HuR expression has been connected with aggressive behavior of several malignancies. Cyclooxygenase-2 (COX-2) is also expressed in several malignant tumors, and its expression is regulated by HuR. Tissue microarray of 153 primary pheochromocytomas and paragangliomas was investigated for the expression of HuR and COX-2 proteins by immunohistochemistry using two different HuR antibodies (HuR19F12 and HuR3A). In these tumors, the expression of both intranuclear and cytoplasmic HuR was detectable. Increased cytoplasmic HuR expression was significantly associated with metastatic tumors. Increased COX-2 and MIB-1 expression also was associated with metastatic potential, and moreover, HuR and COX-2 expression correlated with each other. Our data suggest that increased expression of HuR protein is associated with metastatic potential of paragangliomas and pheochromocytomas, and COX-2 seems to be a target of HuR.

Oncogenic features of the bone morphogenic protein 7 (BMP7) in pheochromocytoma.

BMP7 is a growth factor playing pro- or anti-oncogenic roles in cancer in a cell type-dependent manner. We previously reported that the BMP7 gene is overexpressed in pheochromocytomas (PCCs) developing in MENX-affected rats and human patients. Here, analyzing a large cohort of PCC patients, we found that 72% of cases showed elevated levels of the BMP7 protein. To elucidate the role of BMP7 in PCC, we modulated its levels in PCC cell lines (overexpression in PC12, knockdown in MPC and MTT cells) and conducted functional assays. Active BMP signaling promoted cell proliferation, migration, and invasion, and sustained survival of MENX rat primary PCC cells. In PCC, BMP7 signals through the PI3K/AKT/mTOR pathway and causes integrin β1 up-regulation. Silencing integrin β1 in PC12 cells suppressed BMP7-mediated oncogenic features. Treatment of MTT cells with DMH1, a novel BMP antagonist, suppressed proliferation and migration. To verify the clinical applicability of our findings, we evaluated a dual PI3K/mTOR inhibitor (NVP-BEZ235) in MENX-affected rats in vivo. PCCs treated with NVP-BEZ235 had decreased proliferation and integrin β1 levels, and higher apoptosis. Altogether, BMP7 activates pro-oncogenic pathways in PCC. Downstream effectors of BMP7-mediated signaling may represent novel targets for treating progressive/inoperable PCC, still orphan of effective therapy.

Vascular Pattern Analysis for the Prediction of Clinical Behaviour in Pheochromocytomas and Paragangliomas

Pheochromocytomas (PCCs) are neuroendocrine tumors arising from chromaffin cells of the adrenal medulla. Related tumors that arise from the paraganglia outside the adrenal medulla are called paragangliomas (PGLs). PCC/PGLs are usually benign, but approximately 17% of these tumors are malignant, as defined by the development of metastases. Currently, there are no generally accepted markers for identifying a primary PCC or PGL as malignant. In 2002, Favier et al. described the use of vascular architecture for the distinction between benign and malignant primary PCC/PGLs. The aim of this study was to validate the use of vascular pattern analysis as a test for malignancy in a large series of primary PCC/PGLs. Six independent observers scored a series of 184 genetically well-characterized PCCs and PGLs for the CD34 immunolabeled vascular pattern and these findings were correlated to the clinical outcome. Tumors were scored as malignant if an irregular vascular pattern was observed, including vascular arcs, parallels and networks, while tumors with a regular pattern of short straight capillaries were scored as benign. Mean sensitivity and specificity of vascular architecture, as a predictor of malignancy was 59.7% and 72.9%, respectively. There was significant agreement between the 6 observers (mean κ = 0.796). Mean sensitivity of vascular pattern analysis was higher in tumors >5 cm (63.2%) and in genotype cluster 2 tumors (100%). In conclusion, vascular pattern analysis cannot be used in a stand-alone manner as a prognostic tool for the distinction between benign and malignant PCC, but could be used as an indicator of malignancy and might be a useful tool in combination with other morphological characteristics.

Cytoplasmic Staining of OCT4 Is a Highly Sensitive Marker of Adrenal Medullary–derived Tissue

OCT4 immunostaining has become an essential resource in diagnosing germ cell neoplasia. OCT4 is a transcription factor with a characteristic nuclear staining pattern specific to germ cell neoplasms. Our institution has observed that paraganglionic tissue consistently displayed intense cytoplasmic staining by utilizing monoclonal OCT4 antibody, and we intended to determine whether OCT4 could provide additional diagnostic utility in adrenal tumors. We used monoclonal and polyclonal OCT4 antibodies for comparison of staining patterns and intensities. Thirty-eight pheochromocytomas (8 metastatic), 22 adrenal cortical carcinomas (2 metastatic), 15 metastatic tumors to the adrenal glands, and 10 normal adrenal glands containing cortical and medullary tissue were immunostained with OCT4. A 4-tier system (0 to 3), for recording intensity and extent of cytoplasmic staining, was used. All 30 primary pheochromocytomas displayed strong and diffuse (3+3) cytoplasmic immunoexpression. Six of 8 metastatic pheochromocytomas showed strong immunoexpression (3+3), whereas the remaining 2 showed moderate intensity (2+3). All 22 adrenal cortical carcinomas, including metastatic cases, were completely negative. Only 2 metastatic tumors to the adrenal gland showed weak, cytoplasmic positivity: a small cell carcinoma and a Merkel cell carcinoma. Controls stained in an appropriate nuclear manner. Immunoelectron microscopy demonstrated the antibody interacting with neurosecretory granules. To our knowledge, the cytoplasmic expression of OCT4 in adrenal medulla and pheochromocytoma has not been specifically studied. The goal of this study is to analyze the immunoreactivity of adrenal cortical carcinoma and pheochromocytoma to OCT4 and determine the sensitivity and specificity of this particular staining pattern and to compare monoclonal and polyclonal antibodies.

Immunohistochemical Evidence of Dysregulation of the Mammalian Target of Rapamycin Pathway in Primary and Metastatic Pheochromocytomas

To characterize the status of the mammalian target of rapamycin pathway using formalin-fixed, paraffin-embedded specimens from patients with primary and metastatic pheochromocytoma. Tissue microarrays were built from 19 normal adrenal medullas, 39 primary pheochromocytomas, and 8 unrelated metastatic pheochromocytomas. In 2 of the 8 cases of metastatic pheochromocytoma tissues, samples from the primary tumor were available. The expression levels of phosphatase and tensin homolog, phosphorylated Akt, phosphorylated S6, p27, and c-myc were evaluated by immunohistochemistry. The levels of phosphatase and tensin homolog and p27 were greater in the nontumor tissue than in the primary and metastatic pheochromocytomas. Increasing levels of phosphorylated Akt were noted in the nontumor adrenal medulla, primary pheochromocytomas, and metastatic pheochromocytomas. Finally, the levels of phosphorylated S6 were greater in the metastatic pheochromocytomas than in the nontumor adrenal medulla and primary pheochromocytomas. We found evidence of dysregulation of the mammalian target of rapamycin pathway in primary and metastatic pheochromocytomas, with increased phosphorylated S6 and phosphorylated Akt, and decreased phosphatase and tensin homolog and p27 expression levels. Because the currently available treatment modalities are less than optimal, our findings lend additional support to continuing to explore the utility of mammalian target of rapamycin pathway-targeted therapy for pheochromocytomas.

Expression of the Transcription Factor Snail and Its Target Gene Twist Are Associated with Malignancy in Pheochromocytomas

One of the best known functions of the zinc-finger transcription factor Snail is to induce epithelial-mesenchymal transition (EMT). Twist, a target genes of Snail, is known to promote the development of distant metastases in mice. Increasing evidence suggests that EMT plays a pivotal role in tumor progression and metastatic spread. Snail, Twist, and E-cadherin expression were assessed by immunohistochemistry and real-time quantitative reverse transcriptase-polymerase chain reaction in 12 malignant and 35 benign pheochromocytomas (PCC). Data were correlated with clinical characteristics and genetics. We found Snail expression in 13 (28%) of 47 primary PCC samples. Twist was expressed in 31 (66%) of 47 cases. Only one of 47 PCC showed E-cadherin expression. We observed Snail expression in 7 (58%) of 12 malignant PCC, whereas only 6 (17%) of 35 apparently benign PCC revealed Snail expression (P = 0.01). Furthermore, 11 (92%) of 12 malignant PCC, but only 20 (57%) of 35 benign PCC, revealed Twist expression (P = 0.03). Interestingly, all five metastases showed Snail and Twist expression. In normal adrenal medulla, Snail, Twist, and E-cadherin expression could not be detected. We describe for the first time that EMT markers Snail and Twist are expressed in PCC and that their expression is associated with malignancy. Our study supports a role for EMT in the malignant transformation of PCC.

Mediastinal Pheochromocytoma with Single Coronary Blood Supply: A Case Report

Primary pheochromocytomas located outside the adrenal glands account for only 10% of all pheochromocytomas. Mediastinal pheochromocytomas are even rarer and usually represent a therapeutic challenge as they often infiltrate adjacent structures. We report the case of a large primary mediastinal pheochromocytoma in a 65-year-old patient presenting with a sudden angina-like chest pain and dyspnea. Thoracic multislice computed tomography showed an 8 x 5 x 6-cm retrocardiac mass causing compression of both atria and infiltrating the left superior pulmonary vein. The tumor was highly vascularized and presented a blood supply derived from the circumflex artery. The mass was successfully removed by open heart surgery, and the patient was discharged 10 days postoperatively.

Cardiac Pheochromocytomas Detected by Tc-99m-Hydrazinonicotinyl-Tyr3-Octreotide (HYNIC-TOC) Scintigraphy

Primary pheochromocytomas of the heart are extremely rare tumors and difficult to diagnose. Iodine labeled metaiodobenzylguanidine (MIBG) is the first choice of the nuclear medicine modality in the evaluation of adrenal pheochromocytoma. However, the sensitivity of MIBG in the diagnosis of extraadrenal pheochromocytoma is less optimal. In this preliminary report, the efficacy of octreotide scintigraphy using Tc-99m labeled hydrazinonicotinyl-Tyr3-octreotide (HYNIC-TOC) in the evaluation of primary cardiac pheochromocytoma was assessed.

Laparoscopic and Retroperitoneoscopic Treatment of Pheochromocytomas and Retroperitoneal Paragangliomas: Results of 161 Tumors in 126 Patients

Laparoscopic and retroperitoneoscopic excisions of pheochromocytomas and retroperitoneal paragangliomas are challenging surgical procedures because of extensive intraoperative catecholamine release, extreme vascularization, and demanding localization. In a prospective clinical study 161 chromaffine neoplasias (134 pheochromocytomas, 27 paragangliomas) were removed endoscopically in 126 patients (67 males, 59 females, age 41.7 +/- 16.4 years; 130 operations). Six patients showed multiple (2-5) tumors. Tumor size ranged from 0.5 to 12 cm (mean 3.5 +/- 1.9 cm). Forty-two patients suffered from hereditary diseases. Twenty-four patients had bilateral adrenal diseases; in 14 patients pheochromocytomas were removed on both sides synchroneously. Ten neoplasias were local or loco-regional recurrences (7 pheochromocytomas, 3 paragangliomas). The laparoscopic route was chosen in 16 operations; the retroperitoneoscopic technique was performed in 128 others. Partial adrenalectomies were performed in 57 operations (in all but one of the patients with bilateral disease). High-dosage alpha-blockade with phenoxybenzamine was routinely used. Conversion to open surgery occurred once. Perioperative complications were minor (17%); mortality was zero. Operating time for unilateral retroperitoneoscopically removed primary pheochromocytomas (n = 113) was 82 +/- 49 minutes (range: 20-300 minutes) and depended on tumor size (< 3 cm vs. > or = 3 cm; P < 0.05) and gender (P < 0.001), but not on extent of resection (partial vs. total, P = 0.266). Operating time for paragangliomas ranged from 55 to 600 minutes. Median blood loss was 20 ml. Median duration of postoperative hospitalization was 4 days. In 22 of 24 patients with bilateral disease, complete preservation of cortical function was achieved. Locoregional and/or distant metastatic recurrence were found in 5 patients. Endoscopic removal of solitary, bilateral, multiple, and recurrent pheochromocytomas and retroperitoneal paragangliomas is feasible and safe, but surgeons need extensive experience in minimally invasive techniques, as well as in endocrine surgery.

Primary meningeal pheochromocytoma: case report

Intracranial pheochromocytomas are extremely rare tumors. Reported cases include metastatic tumors without known cases of primary pheochromocytomas. A female patient with a history of a surgically treated adrenal pheochromocytoma presented 23 years later with headache, nausea and blood hypertension. A head CT scan demonstrated a right temporoparietal meningeal heterogeneous lesion with a surrounding hyperdense ring. No other lesions were disclosed. The lesion developed in the inner and outer surface of the dura without brain infiltration and it was totally resected. The patient is free of disease 6 years after brain surgery. To our knowledge this is the first reported case of a primary meningeal pheochromocytoma.

VEGF in 105 pheochromocytomas: enhanced expression correlates with malignant outcome.

Pheochromocytomas are rare sympathoadrenal tumors that are highly vascular. Their malignancy is extremely difficult to estimate on the basis of histopathological features. Vascular endothelial growth factor (VEGF) is one of the most important angiogenic factors involved in both tumor growth and metastasis. In our search for new prognostic markers, we investigated the expression of VEGF in normal adrenal gland, in 105 primary pheochromocytomas, and in 6 metastases by using immunohistochemistry and Northern blot analysis. We also calculated the microvessel density of these tumors by staining the endothelial cells with monoclonal CD34 antibody. VEGF messenger ribonucleic acid was found in all pheochromocytomas studied. Immunohistochemically, VEGF was not found in normal adrenal medullary cells. Interestingly, all malignant pheochromocytomas (n=8), regardless of their primary location, had strong or moderate VEGF immunoreactivity, while most benign adrenal pheochromocytomas (26 of 37, 70.3%) were either negative or only weakly positive. The staining was heterogenous in extraadrenal pheochromocytomas as well as in a group of tumors that had histologically suspicious features but had not metastasized, here called borderline tumors (n=29). The microvessel density varied greatly in all of the tumor groups, and no statistical difference was found between these groups. Here we report moderate to strong VEGF expression in malignant pheochromocytomas, and negative or weak expression in benign adrenal pheochromocytomas. Normal medullary cells are immunohistochemically negative. Thus, low VEGF expression in pheochromocytomas favors a benign diagnosis.

KI-67 AND hTERT Expression Can Aid in the Distinction between Malignant and Benign Pheochromocytoma and Paraganglioma

The clinical and histopathological distinction between benign and malignant pheochromocytomas and paragangliomas is difficult, and reliable diagnostic markers are lacking. Here we have evaluated the prognostic value of human telomerase reverse transcriptase (hTERT) gene expression detected by reverse transcription PCR (RT-PCR); telomerase activity (TA) measured by TRAP (telomeric repeat amplification protocol) assay; immunohistochemical staining for Ki-67/MIB-1; and the mRNA expression of matrix metalloproteinase (MMP)–2 and EMMPRIN (extracellular matrix metalloproteinase inducer) analyzed by in situ hybridization in 32 primary pheochromocytomas or abdominal paragangliomas. hTERT was expressed in 7/11 malignant tumors (defined as presence of metastasis and/or extensive local invasion) as compared with in 2/21 benign tumors. All of the benign tumors showed <1% proliferative activity, as measured by Ki-67/MIB-1 staining. In all three patients with malignant tumors who developed metastases and/or invasive local recurrence during follow-up, the tumors were positive for either hTERT expression or Ki-67/MIB-1 immunoreactivity. TA was not a significant discriminator between benign and malignant tumors, and the value of EMMPRIN and MMP-2 as predictive markers was limited. In conclusion, the findings imply that the combined use of Ki-67/MIB-1 and hTERT, in addition to histopathology, provides a highly specific tool to identify benign pheochromocytoma and abdominal paraganglioma cases that are not at risk of developing recurrent or metastatic disease.

Increased expression of cyclooxygenase-2 in malignant pheochromocytomas.

Pheochromocytomas are rare tumors of the adrenal medulla or the paraganglion system. There are no histological or chemical markers available that define the malignant behavior of these tumors; so far only the discovery of metastases reveals malignancy. Cyclooxygenase (Cox) is the key enzyme in conversion of arachidonic acid to PGs, and two isoforms, Cox-1 and Cox-2, have been identified. Cox-2 has been associated with carcinogenesis, and it is overexpressed in many human malignancies. We have now investigated the expression of Cox-2 in normal adrenal gland, in 92 primary pheochromocytomas and in six metastases using immunohistochemistry and Northern blot and Western blot analyses. Cox-2 protein was expressed in the adrenal cortex, whereas the medulla was negative as detected by immunohistochemistry. Interestingly, all malignant pheochromocytomas (n = 8), regardless of the primary location of the tumor, showed moderate or strong Cox-2 immunoreactivity, whereas 75% of the benign adrenal tumors (n = 36) showed no or only weak immunopositivity. The staining was negative or weak in 79% of the adrenal tumors that showed histologically suspicious features (n = 24), but had not metastasized. Most of the pheochromocytoma samples studied also expressed low levels of Cox-2 mRNA. Our data show that normal adrenal medulla does not express Cox-2 immunohistochemically. However, strong Cox-2 protein expression was found in malignant pheochromocytomas, whereas most benign tumors expressed Cox-2 only weakly. To our knowledge, this is the first report on Cox-2 expression in pheochromocytomas and enhanced expression in malignant pheochromocytomas. These findings suggest that negative or weak Cox-2 expression in pheochromocytomas favors benign diagnosis.

Cardiac pheochromocytoma

Primary pheochromocytomas of the heart are extremely uncommon. In this report, we present the case of a patient with primary cardiac pheochromocytoma arising from the interatrial septum. Metaiodobenzylguanidine-scintigraphy was negative and diagnosis was confirmed by a positive octreotide scintiscan. The tumor was removed successfully using cardiopulmonary bypass.

(123)I]metaiodobenzylguanidine and [(111)In]octreotide uptake in begnign and malignant pheochromocytomas.

Selecting the appropriate approach for resection and follow-up of pheochromocytomas (PCCs) is highly dependent upon reliable localization and exclusion of multifocal, bilateral, or metastatic disease. Metaiodobenzylguanidine (MIBG) scintigraphy was developed for functional localization of catecholamine-secreting tissues. Somatostatin receptor imaging (SRI) has a high sensitivity for localizing head and neck paragangliomas, but studies of intraabdominal PCCs are rare. In this study we review our experience of [(123)I]MIBG and SRI, performed since 1983 and 1989, respectively, in the work-up of primary and recurrent PCCs. Scintigraphic results were correlated with catecholamine secretion, size and site, malignancy, associated tumor syndromes, and morphological features. [(123)I]MIBG scans were performed in a total of 75 patients, in 70 cases before resection of primary PCCs and in 5 cases because of recurrent disease. Ninety-one PCCs were resected. The overall detection rates were 83.3% and 89.8% for PCCs larger than 1.0 cm. Multifocal disease was detected in 4 patients with [(123)I]MIBG. [(123)I]MIBG uptake correlated with greater size of PCC (r = 0.33; P = 0.008) and greater concentration of plasma epinephrine (r = 0.32; P = 0.006). [(123)I]MIBG-negative PCCs (n = 14) had significantly (P = 0.01) smaller diameters than [(123I)]MIBG-positive tumors. Furthermore, [(123)I]MIBG uptake was significantly higher in unilateral (P = 0.02), benign (P = 0.02), sporadic (P = 0.02), intraadrenal (P = 0.02), and capsular invasive (P = 0.03) PCCs than in bilateral, malignant, MEN2A/2B-related, extraadrenal, and noninvasive PCCs, respectively. The detection rate of SRI was only 25% (8 of 32) for primary benign PCCs. In 14 patients metastases occurred, which were effectively visualized with [(123)I]MIBG in 8 of 14 cases. SRI was able to detect metastases in 7 of 8 cases, including 3 [(123)I]MIBG-negative metastatic cases. In addition, [(123)I]MIBG and SRI detected 2 recurrences. In conclusion, [(123)I]MIBG uptake is correlated with the size, epinephrine production, and site of PCCs. Its role in bilateral and MEN2A/2B-related PCCs seems limited. In cases of recurrent elevation of catecholamines, localization of metastases and/or recurrence should be attempted with [(123)I]MIBG scintigraphy. In suspicious metastatic PCCs, SRI might be considered to supplement [(123)I]MIBG scintigraphy.

Pheochromocytoma and Paraganglioma: Comparison of MR Imaging With CT and I-131 MIBG Scintigraphy

To ascertain the magnetic resonance (MR) imaging characteristics of pheochromocytomas and paragangliomas and to compare MR with computed tomography (CT) and iodine-131 metaiodobenzylguanidine (I-131 MIBG), 19 patients (18 with pheochromocytomas, one with a paraganglioma) were studied. The 18 patients with pheochromocytomas had had positive findings with I-131 MIBG scintigraphy. Abdominal pheochromocytomas were generally hypointense compared with normal liver on T1-weighted MR images and extremely hyperintense on T2-weighted MR images. MR imaging was preferable to CT in the evaluation of primary pheochromocytomas due to superior tissue characterization, particularly in the patient with hypertension and borderline catecholamine levels. For patients with recurrent or metastatic disease, the data suggest that I-131 MIBG scintigraphy is the examination of choice.