Localization Of Pheochromocytoma Research Articles

Pheochromocytoma/paraganglioma: clinical and genetic aspects

The present retrospective descriptive and analytical study included 167 patients divided into three groups. Two groups were comprised of the patients with genetically predetermined pheochromocytoma (type 2 MEN syndrome and von Hippel-Lindau disease respectively), the third croup consisted of the patients presenting with sporadic pheochromocytoma. The median age at which pheochromocytoma was diagnosed was 25 years in group 1, 18 years in group 2, and 47 years in group 3. Adrenalin-type secretion was predominated in group 1 in contrast to the noradrenalin-type and mixed-type secretion in the patients of groups 2 and 3 respectively. The patients of group 1 showed positive correlation between the tumour size and excretion of methylated catecholamines. 82% of these patients exhibited bilateral adrenal lesions and 58% suffered multifocal lesions; no cases of extra-adrenal localization of the tumour were documented. The extra-adrenal localization of pheochromocytomas was observed in 16.4% of the patients in group 2, where 6.6% of the patients had metastases. No metastases of pheochromocytoma were found in the patients of groups 1 and 3. It is concluded that the patients under the age of 40 presenting with bilateral and multicentral pheochromocytoma with the aggravated familial history need the genetic predetermination of the disease to be excluded taking into account syndromal symptoms. Examination for the detection of type 2 MEN is not required in the patients showing isolated normetanephrin excretion. Nor is the search for metastases of pheochromocytoma and its extra-adrenal localization is necessary in the patients presenting with type 2 MEN syndrome and/or exhibiting isolated metanephrin excretion.

Intraindividual Comparison of 123I-mIBG SPECT/MRI, 123I-mIBG SPECT/CT, and MRI for the Detection of Adrenal Pheochromocytoma in Patients With Elevated Urine or Plasma Catecholamines

To determine the diagnostic performance of ¹²³I-metaiodobenzylguanidine (mIBG) SPECT/MRI fusion, ¹²³I-mIBG SPECT/CT and adrenal MRI for the detection of pheochromocytoma in patients with elevated urine or plasma catecholamines. Twenty-two consecutive patients underwent both a whole-body ¹²³I-mIBG scan with SPECT/CT of the adrenal region and MRI of the adrenal glands. Fused SPECT/MRI, SPECT/CT, and MRI scans were evaluated. Imaging results were analyzed both on a per-patient and on a per-lesion basis. Histopathology and/or clinical and radiological follow-up served as the reference standard. Sixteen adrenal tumors were found in thirteen patients. On a per-lesion basis, SPECT/CT had a sensitivity of 87.5%, a specificity of 93.8%, and an overall accuracy of 92.5%. MRI had a sensitivity of 87.5%, a specificity of 96.9%, and an overall accuracy of 95.0%. On a per-patient basis, both SPECT/CT and MRI had a sensitivity of 85.7%, a specificity of 93.3%, and an overall accuracy of 90.9%. SPECT/CT was concordant with MRI in 81.8% of cases. SPECT/MRI fusion was superior to both SPECT/CT and MRI and had a sensitivity of 100% on both a per-lesion and a per-patient basis. ¹²³I-mIBG SPECT/MRI has the highest sensitivity and accuracy for the detection and localization of pheochromocytomas. SPECT/CT and MRI of the adrenal glands are equivalent diagnostic procedures. However, MRI offers the advantage of fully diagnostic assessment of adrenal lesions other than pheochromocytoma undetectable by ¹²³I-mIBG.

Simultaneous Adrenal Pheochromocytoma and Carotid Body Paraganglioma in a Woman

Simultaneous occurrence of carotid body tumor and pheochromocytoma is rare. Most pheochromocytomas have grown on adrenal medulla, but some of the pheochromocytoma patients have multifocal paragangliomas arising from extraaderenal tissues [1–3]. Pheochromocytomas and paragangliomas occur as sporadic tumors or they can be associated with several hereditary syndromes such as (1) multiple endocrine neoplasia type 2 (MEN 2), (2) Von-Hippel-Lindau disease (VHL) and (3) neurofibromatosis type 1 as an unusual genetic cause of pheochromocytomas. Genetic testing is recommended for patients with an apparently sporadic pheochromocytoma under the age of 20 years with a family history or features suggestive of hereditary pheochromocytoma or for patients with sympathetic paragangliomas [4, 5]. For individuals who do not meet these criteria, genetic testing is optional. Discovery of pheochromocytoma or paraganglioma in a patient should lead to a careful search to rule out multifocal lesions and/or hereditary syndromes. The diagnosis of pheochromocytoma and paraganglioma is made by biochemical testing, and imaging is done to localize the tumor for surgical planning [6, 7]. F-18 FDG PET has proved to be an effective tool in the localization of pheochromocytomas and paragangliomas (Figs. ​(Figs.11 and ​and22). Fig. 1 A 45-year-old female was admitted to the hospital with uncontrolled hypertension. In laboratory analysis, urine norepinephrine was 26.0 μg/24 h (normal, 12.1–85.5), epinephrine was 8.3 μg/24 h (normal, ... Fig. 2 Surgical excision was performed for a right carotid mass and right adrenal mass. The microscopic findings of the adrenal mass (a) showed a typically organoid pattern (‘Zellballen’) of the normal paraganglion, which is composed of two cell ...

Diagnosis of pheochromocytoma

Sir, Pheochromocytoma is a rare tumor of chromaffin cells accounting for less than 0.3% of all cases of hypertension. Majority of them are benign and are a surgically curable cause of hypertension. Aggressive diagnostics and surgical intervention are recommended because failure to diagnose the tumor can result in uncontrolled catecholamines release leading to catastrophic consequences.[1] Many biochemical diagnostic tests and imaging modalities exist for diagnosis and localization of tumor; however, optimum approach remains debatable. A 21-kg, 11-year-old boy presented with a history of hypertension, occasional headache, vomiting, and perspiration since 2 months. His pulse rate was 110/min and blood pressure 150/106 mm of Hg. Electrocardiogram was suggestive of left ventricular hypertrophy (LVH). On ultrasound examination a 2.9 × 2.7 cm mass was seen at renal hilar region. Contrast computed tomography (CT) scan showed a 3.7 × 2.6 × 2.5 cm hypodense well-defined enhancing mass lesion with nonenhancing central cystic lesion near the left renal hilum medially. Left adrenal gland was seen to be separate from the mass lesion, suggesting a retroperitoneal mass, possibly an extra-adrenal pheochromecytoma. Urinary vanillyl-mandelic-acid (VMA) and urinary total metanephrines, estimated by column chromatography, were 6.35 mg/24 h (normal - 1.90 to 13.60) and 0.59 mg/24 h (normal – 0.00 to 0.90), respectively. All hematological investigations were within normal limits. In view of negative biochemical test results and possibility of extra-adrenal pheochromocytoma, Iodine 131 labeled meta-iodo-benzyl-guanidine (131I MIBG) scan was performed which suggested negative result. The preoperative 2D echocardiography suggested LVH with ejection fraction (EF) 50%. Fundus examination showed grade IV hypertensive retinopathy. With a provisional diagnosis of extra-adrenal pheochromocytoma, oral phenoxybenzamine 10 mg thrice a day was started and gradually increased up to 40 mg thrice a day. Oral propranolol (20 mg) thrice a day was started after 4 days to control heart rate. After 10 days of preoperative preparation, patient was subjected to retroperitoneal laparoscopic removal of tumor. The tumor was found to be arising from adrenal gland and extending up to the renal hilum. Histopathological examination confirmed the diagnosis of pheochromocytoma. This case raises several questions related to reliability of tests used for the diagnosis and localization of pheochromocytoma. The diagnosis of pheochromocytoma depends on demonstration of excessive production of catecholamines or its metabolites in urine or plasma. 24 h urine tests are considered superior to plasma tests mainly because tumor often secrete catecholamines intermittently and the short half-life of catecholamines can result in relatively normal plasma catecholamine levels even in the presence of a functional tumor. Measurement of VMA in urine is relatively inexpensive, easy to perform, and although it has acceptable specificity (95%), it has a low sensitivity (64%). Urinary total metanephrines has a similar specificity but higher sensitivity (77%) and several studies have found it to be the most sensitive test for the diagnosis of pheochromocytoma. All these biochemical tests were negative in spite of a clinically active tumor in the patient. The amounts of unmetabolized catecholamines or metabolic products released from tumor were possibly not high enough to provide abnormal urinary values, although they were sufficient to provoke the typical symptomatology. Measurement of free metanephrines in plasma has emerged as promising and reliable initial test in the diagnosis of pheochromocytoma compared to conventional tests with sensitivity of 99% and specificity of 89%.[23] Plasma-free metanephrines are produced continuously by metabolism of catecholamines within pheochromocytoma tumor cells and are relatively unaffected by sympathoadrenal excitation. In contrast VMA and the total metanephrines measured in urine are produced in different parts of the body by metabolic processes not directly related to the tumor itself. MIBG offers an approach to overcome the limitations of anatomic imaging. The diagnostic specificity of MIBG has been reported close to 100%[45] as it is concentrated, released, and stored in the chromaffin granules; however, it was negative in our case probably due to necrotic lesion suggestive on CT scan. CT and magnetic resonance imaging (MRI) are believed to be the best-available anatomic imaging techniques and choice depends on institutional preference. Both imaging studies have excellent sensitivity but lack adequate specificity for unequivocally confirming a mass such as a pheochromocytoma. The recent introduction of combined positron emission tomography/CT scanning has emerged as a promising test but is not widely available.

Is there still a place for adrenal venous sampling in the diagnostic localization of pheochromocytoma?

Our objective is to outline the utility of adrenal venous sampling (AVS) with measurements of metanephrine to normetanephrine ratios for diagnostic localization of phaeochromocytoma in a patient with normal plasma levels of catecholamines. A 53-year-old-woman was referred for evaluation of recurrent pheochromocytoma following a right adrenalectomy 14 years earlier. Diagnosis of recurrent disease was established from elevations in plasma metanephrines with normal levels of catecholamines. Magnetic resonance imaging indicated two 1-2 cm masses in the right surgical bed and another 1-1.5 cm mass in the left adrenal. These masses were negative on (123)I-metaiodobenzylguanidine scintigraphy. There was no evidence of a hereditary syndrome. We, therefore, carried out two investigational approaches to identify the tumor masses. Hybrid positron emission tomography/computed tomography with (68)Ga-DOTATOC ((68)Ga-DOTATOC-PET/CT) confirmed the presence of recurrent disease in the right surgical bed and also suggested additional left adrenal involvement. Normal plasma catecholamines precluded the use of adrenal venous sampling (AVS) with catecholamine measurements. Hence, we performed AVS with measurements of plasma metanephrines, which were 4- to 7-fold higher in the left adrenal vein than in central venous plasma. We observed a reversal of the normally high metanephrine to normetanephrine ratio (mean value ± SD 5.28 ± 1.86; range 3.36-8.84, n = 13) to 0.73, establishing the presence of a left adrenal pheochromocytoma. Surgical pathology confirmed bilateral disease. This case highlights a scenario where a combination of (68)Ga-DOTATOC-PET/CT and AVS with measurement of the metanephrine to normetanephrine ratio was crucial for the preoperative assessment of a patient with bilateral pheochromocytoma.

Laparoscopic Resection of Periadrenal Paraganglioma in a Patient With Multiple Endocrine Neoplasia Type 2A

We report here a case of recurrent pheochromocytoma successfully managed by laparoscopic surgery in a patient with multiple endocrine neoplasia type 2A. A 25-year-old man presented with the contralateral adrenal mass after earlier right adrenalectomy. For the preoperative diagnosis of left adrenal pheochromocytoma, adrenal sparing surgery was considered. From the intraoperative laparoscopic view, we found that the tumor originated in periadrenal sympathetic ganglia, and laparoscopic excision of paraganglioma was successfully performed that preserved the integrity of normal adrenal gland. Extra-adrenal pheochromocytoma is rather rare in MEN 2A and it is important to identify precise intraoperative localization of pheochromocytoma with laparoscopic surgery.

Adrenal Venous Sampling for Catecholamines: A Normal Value Study

Pheochromocytomas are rare, but potentially fatal, neoplasms. The diagnosis and localization of pheochromocytoma can be challenging, and recently there has been some debate regarding the role for adrenal venous sampling (AVS). The utility of AVS in this setting is hampered by a lack of normative value data for adrenal vein catecholamine concentrations and the reliability of lateralization ratios. We sought to address these concerns by analyzing AVS catecholamine concentrations from patients who did not have pheochromocytoma. Eighteen patients underwent successful AVS for evaluation of cortisol-producing adrenal masses. All had normal 24-h urinary excretion of fractionated catecholamines and metanephrines. There was a wide range of catecholamine concentrations in both the right (epinephrine 389-118326 pg/ml; norepinephrine 156-11193 pg/ml) and left (epinephrine 113-9327 pg/ml; norepinephrine 229-2216 pg/ml) adrenal veins. The right adrenal vein-to-left adrenal vein epinephrine gradient was as high as 83:1 (median 2.1:1; P < 0.02). Although less striking, similar findings were also seen for norepinephrine. This report provides a reference range for adrenal vein catecholamine concentrations in nonpheochromocytoma patients and illustrates the wide variation in epinephrine and norepinephrine concentrations. Epinephrine and norepinephrine concentrations are statistically significantly higher in the right vs. the left adrenal vein; in the case of epinephrine, up to an 83-fold difference was found between the right and left adrenal veins. These data highlight why AVS should not be used in the investigation of adrenal pheochromocytoma.

Comparison of 18F-Fluoro-L-DOPA, 18F-Fluoro-Deoxyglucose, and 18F-Fluorodopamine PET and 123I-MIBG Scintigraphy in the Localization of Pheochromocytoma and Paraganglioma

Besides (123)I-metaiodobenzylguanidine (MIBG), positron emission tomography (PET) agents are available for the localization of paraganglioma (PGL), including (18)F-3,4-dihydroxyphenylalanine (DOPA), (18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG), and (18)F-fluorodopamine ((18)F-FDA). The objective of the study was to establish the optimal approach to the functional imaging of PGL and examine the link between genotype-specific tumor biology and imaging. This was a prospective observational study. There were no interventions. Fifty-two patients (28 males, 24 females, aged 46.8 +/- 14.2 yr): 20 with nonmetastatic PGL (11 adrenal), 28 with metastatic PGL (13 adrenal), and four in whom PGL was ruled out; 22 PGLs were of the succinate dehydrogenase subunit B (SDHB) genotype. Sensitivity of (18)F-DOPA, (18)F-FDG, and (18)F-FDA PET, (123)I-MIBG scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI) for the localization of PGL were measured. Sensitivities for localizing nonmetastatic PGL were 100% for CT and/or MRI, 81% for (18)F-DOPA PET, 88% for (18)F-FDG PET/CT, 78% for (18)F-FDA PET/CT, and 78% for (123)I-MIBG scintigraphy. For metastatic PGL, sensitivity in reference to CT/MRI was 45% for (18)F-DOPA PET, 74% for (18)F-FDG PET/CT, 76% for (18)F-FDA PET/CT, and 57% for (123)I-MIBG scintigraphy. In patients with SDHB metastatic PGL, (18)F-FDA and (18)F-FDG have a higher sensitivity (82 and 83%) than (123)I-MIBG (57%) and (18)F-DOPA (20%). (18)F-FDA PET/CT is the preferred technique for the localization of the primary PGL and to rule out metastases. Second best, equal alternatives are (18)F-DOPA PET and (123)I-MIBG scintigraphy. For patients with known metastatic PGL, we recommend (18)F-FDA PET in patients with an unknown genotype, (18)F-FDG or (18)F-FDA PET in SDHB mutation carriers, and (18)F-DOPA or (18)F-FDA PET in non-SDHB patients.

Renal hilar pheochromocytoma: a case report

Paraganglioma is a rare tumor arising from undifferentiated cells of the primitive neural crest. These tumors are most commonly found in the adrenal gland, other localisations are also possible. A 58-year-old woman who presented with history of left lumbar pain, headache, hypertension, palpitation and sweating was found to have a secreting left renal hilar pheochromocytoma. Radical excision of the tumor was therefore undertaken and her hypertension was controlled. From the case report and literature review, the authors suggest a diagnostic and therapeutic strategy for the management of ectopic localization of pheochromocytoma.

Color-coded duplex endoscopic ultrasound of the adrenals

Imaging of the adrenals by endoscopic ultrasound (EUS) is a valuable technique for detection and localization of adrenal lesions, but endosonomorphological tumor distinction remains difficult. In this single-center study, the amount of blood flow in common adrenal lesions, such as adrenal adenomas, adrenal hyperplasia, and pheochromocytomas, was visualized by color-coded duplex EUS (CD-EUS) and was retrospectively analysed. Therefore, we reviewed our EUS database to evaluate and correlate the perfusion patterns of common adrenal lesions with histologically confirmed diagnosis, possible malignancy, and endosonomorphological features such as echogeneity, echostructure, and tumor size. CD-EUS was performed using an endosonoscope Pentax FG 32 UA with a longitudinal 7.5 MHz sector array and Hitachi EUB 525 ultrasound system. In 38 consecutive patients (male=19; female=19; age: mean 53+/-16 yr SD), perfusion patterns of 46 histologically confirmed adrenal, para- or extra-adrenal lesions of adrenal origin (adenoma: no.=20; nodular hyperplasia: no.=11; pheochromocytoma: no.=15; diameter 26+/-15 mm, range 6-70 mm) were analyzed and classified semiquantitatively as "not" (no.=24), "slightly" (no.=12), "moderately" (no.=4) or "highly" (no.=6) hypervascularized. Compared to adenomas (p=0.003) and nodular hyperplasia (p=0.047), pheochromocytomas showed a significantly higher grade of perfusion. There was no relationship between perfusion patterns and localization of pheochromocytomas (adrenal: 8; paraadrenal: 3; extra-adrenal: 4). Vascularization was not statistically associated with tumor echogeneity, echostructure, malignancy or tumor size. CD-EUS is an additional tool for adrenal endosonographic tumor distinction and seems to improve the endosonographic detection of pheochromocytomas by visualization of hypervascularization. As an overlap of perfusion patterns exists, CD-EUS findings must be interpreted in the context of clinical, laboratory and chemical results.

The role of 6-[18F]fluorodopamine positron emission tomography in the localization of adrenal pheochromocytoma associated with von Hippel–Lindau syndrome

[(123/131)I]metaiodobenzylguanidine (MIBG) scintigraphy is considered as the gold standard in the localization of pheochromocytoma. However, this method has less optimal sensitivity for the detection of pheochromocytoma associated with von Hippel-Lindau (VHL). Our preliminary results suggest that this is partially due to the low expression of cell membrane norepinephrine transporter system in VHL-related pheochromocytoma cells. Another probable cause may be the low affinity that [(123/131)I]MIBG has for these cells. Recently, 6-[(18)F]fluorodopamine ([(18)F]DA) positron emission tomography (PET) has been introduced as a novel functional imaging modality with high sensitivity for pheochromocytoma. Therefore, we investigated whether [(18)F]DA PET is more effective than [(123/131)I]MIBG scintigraphy in the diagnostic localization of VHL-related adrenal pheochromocytoma. In this study, we evaluated seven VHL patients in whom adrenal pheochromocytomas were confirmed by histopathology results. Adrenal pheochromocytomas were localized using computed tomography (CT), magnetic resonance imaging (MRI), [(123/131)I]MIBG scintigraphy and [(18)F]DA PET. [(18)F]DA PET localized pheochromocytoma in all the seven patients, as did in CT. In contrast, three out of the seven had negative results utilizing [(123/131)I]MIBG scintigraphy and one out of the six patients had negative MRI results. [(18)F]DA PET was found to show more promising results when compared with [(123/131)I]MIBG scintigraphy in the diagnostic localization of VHL-related adrenal pheochromocytoma, with a 100% rate of localization. Thus, [(18)F]DA PET in conjunction with CT/MRI should be considered as an effective method for the proper localization of VHL-related adrenal pheochromocytoma.

Biochemical Diagnosis and Localization of Pheochromocytoma

Pheochromocytomas can have a highly variable presentation, making diagnosis challenging. To think of the tumor represents the crucial initial step, but establishing the diagnosis requires biochemical evidence of excessive catecholamine production and imaging studies to localize the source. Currently, however, there exist no generally agreed upon guidelines based on which tests and testing algorithms should be used to confirm and locate or exclude a suspected pheochromocytoma. Choice of biochemical tests and imaging studies instead usually depends on institutional experience. At the First International Symposium on Pheochromocytoma (ISP2005), held in Bethesda in October 2005, a panel of experts and patient representatives discussed current problems and available options for tumor diagnosis and localization and formulated recommendations, which were subsequently agreed upon by those in attendance at the meeting. This article summarizes the discussion and recommendations derived from that session.

The Efficacy of MIBG Scan as a Diagnostic and Docalization Test for Pheochromocytoma

Background: Computed tomography (CT) is currently considered as the initial imaging procedure of choice for the localization of pheochromocytomas in most of the cases. 131I-or 123I-Metaiodobenzylguanidine scintigraphy (MIBG scan) was proven to be a highly specific tool for the detection of adrenal and extra-adrenal pheochromocytomas, but was less sensitive than CT. The present study is aimed to evaluate the usefulness of a MIBG scan in diagnosis and localization of pheochromocytoma when compared to CT. Methods: We retrospectively evaluated 27 patients who underwent a MIBG scan for a pheochromocytoma at the Seoul National University Hospital from the year 2000 and 2002. According to the pathological and clinical findings, in 16 the patients pheochromocytoma was confirmed to be positive and the rest 11 of the patients were excluded from the study. Results: Pheochromocytomas was identified in 16 patients. Eleven of them were localized in adrenal gland and 5 were extra-adrenal lesions. The sensitivity to MIBG scan in adrenal lesions and extra-adrenal lesions, was 72% (8/11) and 40% (2/5) respectively. In our study, the overall sensitivity to MIBG scan was 62% (10/16), and overall specificity was 90.9% (10/11). By CT four were identified to have equivocal biochemical abnormalities, but were definite and extraadrenal tumors by MIBG

Abstract #54: Limitation of Imaging Studies in the Localization of Pheochromocytoma

Abstract #54: Limitation of Imaging Studies in the Localization of Pheochromocytoma

Adrenal cortical and medullary imaging

Adrenal disease can be manifested by endocrine dysfunction or anatomic abnormalities detected by cross-sectional imaging modalities. With the advent of newer and more reliable in vitro assays and a better understanding of the spectrum of adrenal pathology, the physician can now adopt a more accurate and cost-effective approach to the diagnosis of adrenal disease. Both functional and anatomic imaging modalities can play an important role in the evaluation of the incidental adrenal mass, the early detection of adrenal metastases, differentiation of the various causes of Cushings's syndrome, selection of patients for potentially curative surgery in primary aldosteronism and adrenal hyperandrogenism, and localization of pheochromocytomas and neuroblastomas. The usefulness of the adrenal cortical radiopharmaceutical, 131I-6-beta-iodomethylnorcholesterol (NP-59), and the adrenal medullary radiopharmaceuticals, 131I and 123I-metaiodobenzylguanidine (MIBG), is detailed for these various clinical settings and the role of NP-59 and MIBG is contrasted to that of the cross-sectional modalities, computed tomography and magnetic resonance imaging (MRI). Incidental adrenal masses are common, but malignancies are few. Imaging studies select those patients who require a further evaluation by biopsy examination or adrenalectomy. In the hyperfunctioning endocrine states, such as Cushing's syndrome, primary aldosteronism, adrenal androgenism, and pheochromocytoma, correlation of biochemical findings with both functional and anatomic imaging is necessary to avoid inappropriate and ineffective surgical intervention, yet not miss an opportunity for curative resection. Lastly, MIBG and MRI are complementary in the detection and staging of neuroblastoma.

Clinical presentation, biochemical parameters and localization of catecholamine-secreting tumors

Background The diagnosis of these catecholamine-secreting tumors requires clinical awareness of the various presentations and syndromes in which these tumors are found. Any suspicion of a pheochromocytoma warrants aggressive diagnostic intervention. The aim of the present paper is to describe clinical manifestations, biochemical work-up and localization of pheochromocytoma. Methods Basic diagnostic method is urinary catecholamines and/or their metabolites. For confirmation, plasma catecholamines, other neuropeptides, and clonidine suppression test can be helpful in confirming the diagnosis. Results Once the diagnosis of pheochromocytomas has been established, alpha receptor blockade should be instituted prior to further investigations. Localization of the tumor is essential prior to surgical intervention. CT or MRI scanning are the first line modalities for localization of these tumors. If CT or MRI scan fails to localize the tumor, the patient has recurrent/malignant disease, or bilateral disease is suspected, then I-131 or I-123 MIBG scanning should be performed. Conclusions Pheochromocytoma are potentially lethal but usually benign tumors. High degree of clinical suspicion and accurate work-up is essential for successful outcome.

Pheochromocytoma: 1926–1993

Pheochromocytoma is a tumor frequently sought and rarely found. It is associated with spectacular cardiovascular disturbances and, when correctly diagnosed and properly treated, it is curable; when undiagnosed or improperly treated, it can be fatal. Catecholamine-producing tumors that arise from chromaffin cells of the adrenal medulla and sympathetic ganglia are termed pheochromocytomas and paragangliomas, respectively. However, the term pheochromocytoma has become the generic name for all catecholamine-producing tumors. The biochemical diagnosis is straightforward. The localization of pheochromocytoma has been greatly facilitated by advances in computerized imaging and meta-iodobenzylguanidine scanning. Treatment with preoperative α- and β-adrenergic blockade followed by surgical excision of the pheochromocytoma are associated with very low morbidity and mortality.

Meta-iodobenzylguanidine Seen in the Diagnosis of Pathologic Conditions of the Adrenal Medulla (Pheochromocytoma)

To the Editor .—Recently, iodine-131-metaiodobenzylguanidine, a compound chemically resembling noradrenaline, accumulated in chromaffin tissue as storage granules. 1,2 Metaiodobenzylguanidine is an adrenergic neuron blocker, an inhibitor of neuronal uptake, and a presynaptic α 2 -agonist. The metaiodobenzylguanidine scan is a safe, specific, and noninvasive procedure for the localization of pheochromocytomas 3,4 ; its limit is the possibility of false-negative scans in 10% of patients, whereas computed tomography (CT) visualizes more than 95% of the intra-adrenal tumors. 5 Brown and colleagues 6 reported a case of a false-positive metaiodobenzylguanidine scan that showed a bilateral adrenal uptake in a patient with a right-sided pheochromocytoma. They concluded that scintigraphy cannot yet replace computed tomography, selected venous sampling, or angiography in the diagnosis of adrenal pheochromocytomas. Fig 1.—Metaiodobenzylguanidine scan showing area of iodine uptake in the right adrenal gland. MIBEG BKG-SUBTRACT. MIBEG DTPA MIBEG + DTPA We report the case of a 30-year-old man who presented

Magnetic resonance imaging of the kidneys and adrenals

Renal and adrenal anatomy, both normal and abnormal, are well depicted by MRI. Although MRI is not a sensitive modality for detection of renal cell carcinoma, it has clinical utility for evaluation of vascular involvement or direct extension of neoplasm into adjacent organs when CT findings are equivocal. Use of signal characteristics has not been useful in differentiating simple from complex cystic renal masses or among the various causes of medical renal disease and renal transplant failure. Similarly, signal characteristics are not sufficiently reliable for differentiating benign from malignant adrenal masses. MRI is useful, however, for detection and localization of pheochromocytomas. MRI plays a major role in imaging of children with neuroblastoma and Wilms' tumor and may obviate other, often more invasive, examinations in these cases.

Scintigraphic studies in adrenal hypertension

Endocrine hypertension secondary to disorders of the adrenal glands is uncommon, but by no means rare. The importance of correct biochemical diagnosis and subsequent localization of the responsible lesion(s) lie in the fact that many of these syndromes occur in younger patients, may exhibit familial patterns of inheritance and are frequently amenable to surgical cure. The radiopharmaceuticals (131)1-6 beta-iodomethyl-19-norcholesterol (NP-59), a marker of adrenocortical cholesterol uptake, and (131)1- and (123)1-metaiodobenzylguanidine (MIBG), a norepinephrine (NE) analog and marker of energy-dependent NE storage vesicle accumulation, can be shown to accurately localize adrenal cortex and sympathoadrenal dysfunction, respectively. In Cushing's syndrome (CS) not only does the pattern of NP-59 uptake depict the adrenal dysfunction and its pathophysiologic basis, but the level of NP-59 accumulation reflects the degree of adrenocortical hyperfunction. Adrenocorticotrophin-independent CS is uniformly and accurately localized, especially in bilateral cortical nodular hyperplasia where even high resolution computed tomography (CT) may fail to depict the often subtle, asymmetric anatomic abnormalities. Dexamethasone suppression NP-59 adrenal scintigraphy has been shown to be highly sensitive and specific, and exceeds the efficacy of CT in the differentiation of adenoma and bilateral hyperplasia in primary aldosteronism. MIBG is useful as a sympathoadrenal imaging agent whose clinical utility has been demonstrated in the localization of pheochromocytoma, especially as a modality to screen the body for multiple and extraadrenal, recurrent, or metastatic lesions. Moreover, the extent of metastatic involvement from neuroblastoma can also be accurately depicted using MIBG. In this review we will examine the role of adrenal scintigraphy in the characterization of hypersecretory disorders of the adrenal cortex, medulla, and related conditions that produce hypertension as part of their symptom(s) complex. This approach, which is complementary to other anatomical modalities of imaging, can be used to advantage in the localization of functioning cortical and medulla adrenal diseases and other neoplasms of adrenergic origin.