Review: Should patients with apparently sporadic pheochromocytomas or paragangliomas be screened for hereditary syndromes?

Aortic Body Tumor in Full-Sibling English Bulldogs

A 10-year-old, neutered male English bulldog died acutely from respiratory distress after a short history of progressive dyspnea. Less than 2 months later, a spayed female full sibling of that dog died suddenly during a nail trim. An aortic body tumor was the cause of death in both dogs based on postmortem and histological examinations. A pheochromocytoma was also diagnosed in the neutered male. Neither dog had a history of brachycephalic airway syndrome, and the implication for a genetic predisposition toward the development of paraganglioma is discussed. This is the first case report of aortic body tumors in sibling dogs, although the condition may not be an uncommon phenomenon.

Succinate dehydrogenase gene mutations are strongly associated with paraganglioma of the organ of Zuckerkandl

Organ of Zuckerkandl paragangliomas (PGLs) are rare neuroendocrine tumors that are derived from chromaffin cells located around the origin of the inferior mesenteric artery extending to the level of the aortic bifurcation. Mutations in the genes encoding succinate dehydrogenase subunits (SDH) B, C, and D (SDHx) have been associated with PGLs, but their contribution to PGLs of the organ of Zuckerkandl PGLs is not known. We aimed to describe the clinical presentation of patients with PGLs of the organ of Zuckerkandl and investigate the prevalence of SDHx mutations and other genetic defects among them. The clinical characteristics of 14 patients with PGL of the organ of Zuckerkandl were analyzed retrospectively; their DNA was tested for SDHx mutations and deletions. Eleven out of 14 (79%) patients with PGLs of the organ of Zuckerkandl were found to have mutations in the SDHB (9) or SDHD (2) genes; one patient was found to have the Carney-Stratakis syndrome (CSS), and his PGL was discovered during surgery for gastrointestinal stromal tumor. Our results show that SDHx mutations are prevalent in pediatric and adult PGLs of the organ of Zuckerkandl. Patients with PGLs of the organ of Zuckerkandl should be screened for SDHx mutations and the CSS; in addition, asymptomatic carriers of an SDHx mutation among the relatives of affected patients may benefit from tumor screening for early PGL detection.

Succinate dehydrogenase - Assembly, regulation and role in human disease

Succinate dehydrogenase (or Electron Transport Chain Complex II) has been the subject of a focused but significant renaissance. This complex, which has been the least studied of the mitochondrial respiratory complexes has seen renewed interest due to the discovery of its role in human disease. Under this heightened scrutiny, the succinate dehydrogenase complex has proven to be a fascinating machine, whose regulation and assembly requires additional factors that are beginning to be discovered. Mutations in these factors and in the structural subunits of the complex itself cause a variety of human diseases. The mechanisms underlying the pathogenesis of SDH mutations is beginning to be understood.

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.

Compound heterozygous mutation with a novel splice donor region DNA sequence variant in the succinate dehydrogenase subunit B gene in malignant paraganglioma

Pheochromocytoma and paraganglioma (PGL) are rare neuroendocrine tumors in children. Apparently sporadic cases of PGL may harbor germline mutations in the succinate dehydrogenase (SDHx) gene. SDHB mutations are associated with malignant disease. We report a 13-year-old African American boy with diffusely metastatic PGL and compound heterozygous mutation leading to a novel splice donor region DNA sequence variant in the SDHB gene. Family history was positive for non-classical congenital adrenal hyperplasia and pituitary adenoma. After surgical resection of the primary PGL and chemotherapy, he was treated with metaiodobenzy lguanidine (MIBG) combined with arsenic trioxide. At 3-year follow-up, he had stable disease.

Paraganglioma syndrome type 1 in a patient with Carney-Stratakis syndrome

BACKGROUND

A 33-year-old man was referred to a specialist center with a left neck mass and hypertension. The patient underwent surgery, which confirmed a malignant neck paraganglioma with metastasis to a cervical lymph node. He had no family history of carotid body tumors or pheochromocytoma.

INVESTIGATIONS

Measurements of plasma free metanephrines and chromogranin A; radiographic evaluations with CT, (18)F-fluorodeoxyglucose PET and (123)I-labeled metaiodobenzylguanidine scan; gene analysis for mutations in the SDHD and the KIT gene.

DIAGNOSIS

Paraganglioma syndrome type 1 in a patient with a paraganglioma, bilateral pheochromocytomas and a gastrointestinal stromal tumor with a somatic Asp579del KIT mutation.

MANAGEMENT

The patient underwent surgical excision of all tumors after adequate preparation with alpha and beta blockers. Blood pressure normalized after surgery. The patient is examined regularly with biochemical and radiographic studies, and his follow-up is expected to last throughout life.

Paraganglioma of the endolarynx: a rare tumor in an uncommon location

Background

Less than 80 reported cases of paragangliomas of the larynx are reported in the literature. A role for external beam radiation in this disease has not yet been explored. We present four cases of laryngeal paragangliomas treated at a large tertiary-care cancer center over a 35-year period.

Methods

124 cases of head and neck paragangliomas treated at a single institution from 1970 to 2005 were retrospectively studied. Patients with laryngeal paragangliomas were identified, and a comprehensive clinico-pathological review was undertaken.

Results

We identified 4 patients with tumors arising in the larynx at the following subsites: supraglottis (2), glottis (1), and subglottis (1). Three patients were treated with surgery and one with definitive radiation alone.

Conclusions

Laryngeal paragangliomas are rare tumors and are adequately treated with surgical resection. We also present one patient who was treated with radiation and had disease stabilization. Accurate histological classification is critical, and the role of genetic testing is emerging.

Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominantly inherited tumor syndrome subclassified into three distinct syndromes: MEN 2A, MEN 2B and familial medullary thyroid carcinoma. In MEN 2 families, medullary thyroid carcinoma, pheochromocytomas and parathyroid adenomas occur with a variable frequency, also depending on the specific genetic defect involved. In 1993, the responsible MEN2 gene was identified. The genetic defect in these disorders involves the RET proto-oncogene on chromosome 10. The germline RET mutations result in a gain-of-function of the RET protein. Extensive studies on large families revealed that there is a strong genotype-phenotype correlation. In this review, guidelines for early diagnosis, including MEN2 gene mutation analysis, and treatment, including preventive surgery, periodic and clinical monitoring, have been formulated, enabling improvement of life expectancy and quality of life. Identification of the RET protein has also provided new insights into its function, and the specific pathways it effects involved in cell proliferation, migration, differentiation and survival. In the near future, identification of biological tumor markers will enable target-directed intervention and may prevent and/or delay progression of both primary and residual tumor growth.

Genetics of chromaffin tumors

The old term of 'chromaffin tumors' encompasses both pheochromocytomas (PHs) and paragangliomas (PGLs). The identification of SDHx genes - new mitochondrial tumor-suppressor genes involved in hypoxia/angiogenesis pathways causing hereditary PGL/PH syndromes - has dramatically changed the genetics of chromaffin tumors. Between 25 and 30% of PGLs/PHs are inherited and are caused by a germline mutation in one of the six susceptibility genes (NF1, RET, VHL, SDHD, SDHB and SDHC). All patients with PGLs/PHs should, therefore, attend genetic counsultations. Genetic testing can be targeted according to family and clinical history. The identification of an inherited disease modifies the management and follow-up of index case and provides an opportunity for predictive genetic testing for other family members.

Dispensable role of protein 4.1B/DAL-1 in rodent adrenal medulla regarding generation of pheochromocytoma and plasmalemmal localization of TSLC1

Protein 4.1B is a membrane skeletal protein expressed in various organs, and is associated with tumor suppressor in lung cancer-1 (TSLC1) in vitro. Although involvement of 4.1B in the intercellular junctions and tumor-suppression was suggested, some controversial results posed questions to the general tumor-suppressive function of 4.1B and its relation to TSLC1 in vivo. In this study, the expression of 4.1B and its interaction with TSLC1 were examined in rodent adrenal gland, and the involvement of 4.1B in tumorigenesis and the effect of 4.1B deficiency on TSLC1 distribution were also investigated using rodent pheochromocytoma and 4.1B-knockout mice. Although plasmalemmal immunolocalization of 4.1B was shown in chromaffin cells of rodent adrenal medulla, expression of 4.1B was maintained in developed pheochromocytoma, and morphological abnormality or pheochromocytoma generation could not be found in 4.1B-deficient mice. Furthermore, molecular interaction and colocalization of 4.1B and TSLC1 were observed in mouse adrenal gland, but the immunolocalization of TSLC1 along chromaffin cell membranes was not affected in the 4.1B-deficient mice. These results suggest that the function of 4.1B as tumor suppressor might significantly differ among organs and species, and that plasmalemmal retention of TSLC1 would be maintained by molecules other than 4.1B interacting in rodent chromaffin cells.

Molecular analysis of the Von Hippel-Lindau (VHL) gene in a family with non-syndromic pheochromocytoma: the importance of genetic testing

The two index patients of the family analyzed in this study had undergone bilateral adrenalectomy for pheochromocytomas. This prompted genetic analyses of the probands and seven first-degree relatives. The two pheochromocytoma patients and two additional asymptomatic family members were found to harbor a mutation c496G>T in exon 3 of the VHL gene. The family was then lost to systematic follow-up. Three years after performing the initial genetic evaluation, the sister of the probands, who was known to carry the same VHL germline mutation, was referred to our service after a pregnancy that was complicated by preeclampsia. She reported paroxysms suggestive for pheochromocytoma, but her urinary metanephrines were negative. However, computerized tomography of the abdomen showed an adrenal mass that was also positive on metaiodobenzylguanidine (MIBG) scintigraphy. This study illustrates that molecular analysis of the index patient(s) can lead to the identification of presymptomatic relatives carrying the mutation. Moreover, despite negative urinary metanephrines, the identification of a specific mutation has led to an increased suspicion and detection of a pheochromocytoma in the sister of the probands.

[Pheochromocytoma - still a challenge]

Pheochromocytomas are rare, mostly benign catecholamine-producing tumors arising from the chromaffin cells of the adrenal medulla or in the paraganglia. Clinical presentation is highly variable but typically with hypertension, severe headaches, palpitations and sweating. Biochemical testing by 24 h urinary fractioned metanephrines or catecholamines and plasma free metanephrines as the most sensitive screening approach, confirms the catecholamine excess. Computed tomography scan and magnetic resonance imaging of the adrenal glands and abdomen as well as functional imaging with (123)Iod-MIBG scintigraphy and (18)F-dopa positron emission tomography are used for tumor localization. Because approximately a quarter of tumors develop secondary to germ-line mutations, screening for genetic alterations is important. The therapy of choice is the endoscopic adrenal sparing surgery following preoperative alpha-blockade. Regular follow-up remains essential due to possible recurrence and malignancy.

An unusual association: pheochromocytoma on an atrophied adrenal gland due to addison's disease

Autoimmune polyendocrine syndrome type II (APS-II) is the most common immunoendocrinopathy syndrome. APS-II is defined by the development of two or more of the following entities: primary adrenal insufficiency (Addison's disease), Graves' disease, type 1A diabetes mellitus, autoimmune thyroiditis, primary hypogonadism, celiac disease, and myasthenia gravis. Other frequent clinical findings are vitiligo, alopecia, pernicious anemia and/or serositis. Primary adrenal insufficiency in these patients affects the adrenal cortex, which is destroyed by autoantibodies against 21-hydroxylase. Unlike other causes of adrenal insufficiency (infectious diseases, infiltrative diseases, bleeding, tumors), the adrenal medulla is not involved. Pheochromocytomas are tumors arising from the chromaffin cells of the sympathetic nervous system in the adrenal medulla. The clinical symptoms of these tumors vary from isolated hypertension or hypertension accompanied by paroxysmal episodes -including the classical triad of headache, palpitations and diaphoresis-to potentially serious manifestations such as acute pulmonary edema, arrhythmias and sudden death. Nevertheless, up to 40% of affected patients are asymptomatic. We present the case of a patient diagnosed with APS-II who developed a pheochromocytoma. In this patient, the adrenal gland cortex was atrophied and the tumor was attached to the adrenal medulla. This coexistence of endocrinopathies, with no etiologic connection, is a surprising finding, which has not previously been described in the current literature.

Pheochromocytoma: diagnostic and therapeutic update

Pheochromocytomas are catecholamine-secreting tumors that arise from chromaffin cells of the sympathetic nervous system. In 80-85% of cases, these tumors are located in the adrenal medulla while the remainder is located in extra-adrenal chromaffin tissues (paragangliomas). Pheochromocytomas account for 6.5% of incidentally discovered adrenal tumors. These tumors may be sporadic or the result of several genetic diseases: multiple endocrine neoplasia type 2, von Hippel-Lindau syndrome, neurofibromatosis type 1, and familial paraganglioma associated with mutations in succinate dehydrogenase subunits. Diagnosis of pheochromocytoma should first be established biochemically by measuring plasma free metanephrines and urinary fractionated metanephrines. The radiological imaging tests of choice are computed tomography (CT) or magnetic resonance imaging (MRI). The first-line specific functional imaging test is scintigraphy with (123)I-metaiodobenzylguanidine (MIBG); if this test is unavailable, scintigraphy with (131)I-MIBG is the second choice. Positron emission tomography (PET) with (18)F-F-fluorodopamine (F-DA) is useful in metastatic disease. The treatment of choice is laparoscopic surgery after adequate alpha adrenergic blockade. Approximately 10% of tumors are malignant. Chemotherapy is used for inoperable disease. Prognosis is good except in malignant disease, in which 5-year survival is less than 50%. The identification of the genes causing hereditary pheochromocytoma has led to changes in the recommendation for genetic testing.

Clinical manifestations of familial paraganglioma and phaeochromocytomas in succinate dehydrogenase B (SDH-B) gene mutation carriers

OBJECTIVE

Phaeochromocytomas and paragangliomas are familial in up to 25% of cases and can result from succinate dehydrogenase (SDH) gene mutations. The aim of this study was to describe the clinical manifestations of subjects with SDH-B gene mutations.

DESIGN

Retrospective case-series.

PATIENTS

Thirty-two subjects with SDH-B gene mutations followed up between 1975 and 2007. Mean follow-up of 5.8 years (SD 7.4, range 0-31). Patients seen at St Bartholomew's Hospital, London and other UK centres.

MEASUREMENTS

Features of clinical presentation, genetic mutations, tumour location, catecholamine secretion, clinical course and management.

RESULTS

Sixteen of 32 subjects (50%) were affected by disease. Two previously undescribed mutations in the SDH-B gene were noted. A family history of disease was apparent in only 18% of index subjects. Mean age at diagnosis was 34 years (SD 15.4, range 10-62). 50% of affected subjects had disease by the age of 26 years. 69% (11 of 16) were hypertensive and 80% (12 of 15) had elevated secretions of catecholamines/metabolites. 24% (6 of 25) of tumours were located in the adrenal and 76% (19 of 25) were extra-adrenal. 19% (3 of 16) had multifocal disease. Metastatic paragangliomas developed in 31% (5 of 16). One subject developed a metastatic type II papillary renal cell carcinoma. The cohort malignancy rate was 19% (6 of 32). Macrovascular disease was noted in two subjects without hypertension.

CONCLUSION

SDH-B mutation carriers develop disease early and predominantly in extra-adrenal locations. Disease penetrance is incomplete. Metastatic disease is prominent but levels are less than previously reported. Clinical manifestations may include papillary renal cell carcinoma and macrovascular disease.

Multiple catecholamine-secreting paragangliomas: diagnosis after hemorrhagic stroke in a young woman

OBJECTIVE

To describe a case of multiple catecholamine-secreting paragangliomas, with a hemorrhagic stroke as the main clinical manifestation.

METHODS

We present a case report with clinical, laboratory, histologic, and genetic details.

RESULTS

A 23-year-old woman with a history of hypertension treated with orally administered medications presented to our emergency department because of sudden onset of hemiplegia of the left side of the body. A computed tomographic scan of the brain showed a right frontoparietal hematoma, and her blood pressure was 185/115 mm Hg. She was admitted to the Department of Neurosurgery, and an external drain was inserted to evacuate the hematoma. She was then referred to the Department of Clinical Sciences, where a search for possible secondary causes of hypertension was undertaken. Substantially elevated urinary levels of vanillylmandelic acid and metanephrines were found, and a pheochromocytoma was suspected. Abdominal computed tomographic scans revealed a large retroperitoneal mass (3.6 by 4 cm) and similar smaller lesions in the right adrenal gland, between the aorta and the vena cava, and in the left paraaortic area. Iodine I 123 metaiodobenzylguanidine scintigraphy showed high uptake in those same areas, consistent with the diagnosis of multiple catecholamine-secreting paragangliomas. After adequate control of the patient's hypertension was achieved with an alpha1-adrenergic receptor blocker, a Ca2+ antagonist, and a beta-adrenergic blocking agent, the tumors were excised in the Department of Surgery. The histopathologic findings confirmed the diagnosis of multiple paragangliomas. The genetic analysis demonstrated an exon 4 mutation in codon 109 (CAA>TAA, Gln>Stop) of the SDHD gene.

CONCLUSION

Although cerebral hemorrhage is an unusual complication of pheochromocytomas or paragangliomas, early recognition of the characteristic symptoms of headache, palpitations, and diaphoresis in a patient with hypertension and prompt appropriate intervention can minimize the morbidity associated with such tumors and prevent a potentially fatal outcome.

Germline SDHB mutations are common in patients with apparently sporadic sympathetic paragangliomas

Germline mutations in the genes encoding the B (SDHB) and D (SDHD) subunits of the heterotetrameric protein succinate dehydrogenase (mitochondrial complex II) are important causes of inherited and apparently sporadic paragangliomas. In an effort to further investigate the role of these genes in malignant sympathetic paragangliomas and adrenal pheochromocytomas, we screened a series of tumors for mutations in SDHB and SDHD. Mutation testing was performed on DNA extracted from formalin-fixed, paraffin-embedded tumors and associated normal tissues by polymerase chain reaction amplification and direct sequencing of the coding regions and intron-exon junctions of the SDHB and SDHD genes. Among 16 malignant paragangliomas with proven metastases, 6 (38%) had mutations in SDHB (2 nonsense, 1 splice site, 1 insertion causing a frameshift, and 2 presumably deleterious missense mutations). Probable deleterious SDHB variants were also detected in 5 (45%) of 11 paragangliomas without known metastatic disease (1 splice site, 1 deletion causing a frameshift, and 3 missense changes). In 12 malignant pheochromocytomas, 1 SDHD and no SDHB mutations were identified. The identical SDHB mutation was detected in DNA extracted from accompanying normal tissue for each of the 10 cases on which this analysis was performed. An excess of SDHB mutations in paragangliomas versus pheochromocytomas was found, with no difference in the frequency of mutations in malignant versus benign paragangliomas. The disparate mutational spectra in malignant paragangliomas and pheochromocytomas may reflect differences in underlying tumor biology.

A novel von Hippel-Lindau point mutation presents as apparently sporadic pheochromocytoma

Von Hippel Lindau disease is a common cause of apparently sporadic pheochromocytomas. Herein, we describe a 20-year-old man with an apparently sporadic pheochromocytoma associated with a novel, relatively conservative germline Gly104Val VHL gene mutation, which is localized within exon 1 of the VHL gene corresponding to the beta -domain of the VHL protein (pVHL). The nearly asymptomatic patient's father also carries the same mutation. Similar to other mutations localized in the same codon, the Gly104Val VHL mutation seems to have an attenuated disease phenotype.

Management of medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is responsible for 13.4% of the total deaths attributable to thyroid cancer in human beings and research on MTC over the last 40 years has identified the RET proto-oncogene as a very relevant component of development of both sporadic and hereditary MTC. An activating germline RET proto-oncogene mutation responsible for a multiple endocrine neoplasia syndrome type 2 (MEN2) or a familial hereditary MTC syndrome is carried by 25% to 35% of patients with MTC. The recognition of RET proto-oncogene mutations by genetic sequencing has allowed us to differentiate hereditary from sporadic MTC, so that it is now possible to identify and treat children at risk for this disease before development of metastasis. Thanks to this discovery, we can now establish the association of MTC with other tumors in the context of MEN2 syndrome; determine adequate follow-up, prognosis, and treatment for patients with hereditary disease; and use this information to develop new therapies against both sporadic and hereditary MTCs.

Germline mutations in PTEN and SDHC in a woman with epithelial thyroid cancer and carotid paraganglioma

BACKGROUND

A 43-year-old woman presented to a cancer genetics clinic for a genetic risk assessment because of her personal history of multiple neoplasias. At 37 years of age, she was diagnosed with multifocal papillary thyroid cancer, and within a year was further diagnosed with a paraganglioma of the left common carotid artery. Two years later, she was diagnosed with a paraganglioma of the right carotid body. All three tumors were treated with surgical resection. There was no family history of malignancy. Past medical history includes uterine leiomyoma and fibrocystic breast disease. Physical examination revealed macrocephaly and papillomatous papules.

INVESTIGATIONS

CT scan of the neck and thorax, 24-hour urine collection for measurement of metanephrines and catecholamines, MRI of the neck, thorax, and abdomen, metaiodobenzylguanidine scan, germline mutation analysis of PTEN, SDHB, SDHC and SDHD.

DIAGNOSIS

Cowden syndrome due to a germline mutation of PTEN, and pheochromocytoma-paraganglioma syndrome due to a germline mutation of SDHC.

MANAGEMENT

Clinical surveillance for breast, endometrial, thyroid, and renal cell carcinoma risks associated with Cowden syndrome according to the National Comprehensive Cancer Network guidelines, annual MRI of the neck, thorax, abdomen and pelvis, annual metabolic screening, and where available, annual 18-fluorodopamine PET scanning, predictive genetic testing of both PTEN and SDHC for the patient's daughter and parents.

Novel SDHD germ-line mutations in pheochromocytoma patients

BACKGROUND

SDHD germ-line mutations predispose to pheochromocytoma (PCC) and paraganglioma (PGL).

MATERIAL AND METHODS

The incidence and types of SDHD germ-line mutations are determined in 70 patients with apparently sporadic adrenal and extra-adrenal PCC.

RESULTS

SDHD sequence variants were identified in the germ line of five patients. Two of three novel mutations were in exon 1 and one in exon 3. One patient had a codon 1 missense mutation (M1K) and a concurrent 3-bp deletion in intron 1. Three of 10 family members had only the exon 1 mutation, whereas one had only the intron 1 mutation. The other exon 1 mutation resulted from a deletion of nucleotides 28-33 with a 12-bp in-frame insertion (c.28_33 del ins TAGGAGGCCCTA). This mutation generated a premature stop codon after codon 9 and was also present in the brother who had a bilateral PCC. The third patient with a carotid body tumour, with an abdominal and a thoracic PGL had a 12-bp deletion in exon 3 (codons 91-94, c.271_282 del). Her father carried the same mutation and had bilateral carotid body tumours. Two further patients, one with six PGL, carried a previously described H50R polymorphism, whose disease-specific relevance is currently unclear. The three patients with bona fide SDHD mutations were younger than those without germ-line mutations.

CONCLUSION

SDHD germ-line mutations are rare in patients with PCC, but their identification is an important prerequisite for the clinical care and appropriate management of affected individuals and their families.

A 25-year-old woman with a gastric GIST and a PET-positive epicardial tumor

BACKGROUND

A 25-year-old woman presented with a history of abdominal pain. Endoscopy of the upper gastrointestinal tract revealed a tumor that protruded into the prepyloric antrum. After resection, a 'high-risk' gastrointestinal stromal tumor was histologically confirmed.

INVESTIGATIONS

Endoscopy, endoscopic ultrasound, hemigastrectomy, [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT scan, histological examination, immunohistochemistry, cardiac MRI, high-resolution CT with electrocardiogram gating, CT angiography, and cardiac surgery.

DIAGNOSIS

Gastrointestinal stromal tumor, epicardial paraganglioma, and Carney's syndrome.

MANAGEMENT

Abdominal ultrasound and endoscopy combined with endoscopic ultrasound, annual FDG-PET/CT scan.

Clinical presentations, biochemical phenotypes, and genotype-phenotype correlations in patients with succinate dehydrogenase subunit B-associated pheochromocytomas and paragangliomas

CONTEXT

Mutations of the gene encoding succinate dehydrogenase subunit B (SDHB) predispose to malignant paraganglioma (PGL). Recognition of the SDHB phenotype in apparently sporadic PGL directs appropriate treatment and family screening.

OBJECTIVE

The objective of the study was to assess mutation-specific clinical and biochemical characteristics of SDHB-related PGL.

DESIGN

The study design was retrospective descriptive.

PATIENTS

PATIENTS included 29 patients (16 males) with SDHB-related abdominal or thoracic PGL.

INTERVENTION

There was no intervention.

MAIN OUTCOME MEASURES

Clinical presentations, plasma and urine concentrations of catecholamines and O-methylated metabolites, and genotype-phenotype correlations were measured.

RESULTS

Mean +/- sd age at diagnosis was 33.7 +/- 15.7 yr. Tumor-related pain was among the presenting symptoms in 54% of patients and was the sole symptom in 14%. Seventy-six percent had hypertension, and 90% lacked a family history of PGL. All primary tumors but one originated from extraadrenal locations. Mean +/- sd tumor size was 7.8 +/- 3.7 cm. In this referral-based study, 28% presented with metastatic disease and all but one eventually developed metastases after 2.7 +/- 4.1 yr. Ten percent had additional head and neck PGLs. The biochemical phenotype was consistent with hypersecretion of both norepinephrine and dopamine in 46%, norepinephrine only in 41%, and dopamine only in 3%. Ten percent had normal catecholamine (metabolite) levels, consistent with biochemically silent PGL. No obvious genotype-phenotype correlations were identified.

CONCLUSIONS

SDHB-related PGL often presents as apparently sporadic PGL with symptoms related to tumor mass effect rather than to catecholamine excess. The predominant biochemical phenotype consists of hypersecretion of norepinephrine and/or dopamine, whereas 10% of tumors are biochemically silent. The clinical expression of these tumors cannot be predicted by the genotype.

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.

Application of Molecular Biology and Genetics in Endocrinology

OBJECTIVE

To review the growing impact of molecular biology and genetics on clinical endocrinology.

METHODS

Medical literature, databases, and Web sites describing genetics and genomic medicine with relevance for clinical endocrinology were reviewed.

RESULTS

Many monogenic disorders can now be explained at the molecular level and the diagnosis can be established through mutational analysis. The ability to establish a molecular diagnosis is relevant for carrier detection and genetic counseling. In contrast to the significant advances in monogenic disorders, the current knowledge about the genetic components contributing to the pathogenesis of complex disorders is still relatively modest and is a major focus of current research efforts. Molecular biology already has an important impact on therapy in endocrine disorders. A broad spectrum of recombinant peptides and proteins are used in daily practice, eg, insulin and insulin analogues. Moreover, the increasingly detailed understanding of the molecular pathogenesis of cancer is leading to the development of novel and more specific inhibitors. While genetic testing has many advantages, it is important that physicians and patients are aware of potential limitations. They include, among others, technical limitations and allelic and nonallelic heterogeneity. These limitations need to be discussed in detail with patients and relatives, and it is often useful to involve a genetic counselor before obtaining informed consent by the individuals undergoing testing.

CONCLUSION

Molecular biology and genetics play an increasingly important role for the diagnosis and therapy of endocrine disorders. Challenges for the future include the elucidation of the genetic components contributing to complex disorders, eg, diabetes mellitus type 2, and the development of cheaper and comprehensive DNA sequencing technologies. Lastly, it is important that there is continuing attention directed towards the ethical, social, and legal aspects surrounding genetic medicine.

RET signaling in endocrine tumors: delving deeper into molecular mechanisms

The rearranged during transfection (RET) proto-oncogene encodes a receptor tyrosine kinase that is implicated in the development of endocrine tumors of the thyroid and adrenal glands. In humans, activating RET mutations are found in the inherited cancer syndrome multiple endocrine neoplasia 2 and in sporadic medullary and papillary thyroid carcinomas. The specific type and location of RET mutations are strongly correlated with the disease phenotype and have both diagnostic and prognostic value. Recent advances in the molecular characterization of the RET receptor and its mutants have begun to define the mechanisms underlying the transforming ability of the different RET mutant forms. This information has revealed key functional features of these mutant proteins that distinguish the different clinically recognized mutations and provide clues as to the functional origins of the phenotypes associated with specific RET mutations. The elucidation of molecular mechanisms involved in RET-mediated transformation is a key step in the development of much needed therapeutics that target RET's oncogenic properties. Recent advances have begun to provide a deeper understanding of the receptor's function, and dysfunction, in human tumors that may guide this process.

LOH on chromosome 11q, but not SDHD and Men1 mutations was frequently detectable in Chinese patients with pheochromocytoma and paraganglioma

Recently, the succinate dehydrogenase subunit D (SDHD) gene has been reported as one of the major susceptibility genes for pheochromocytoma (PCC) and paraganglioma (PGL). In addition, loss of heterozygosity (LOH) on chromosome 11, mainly in 11q23 and 11q13, is observed frequently in PGL. Based on the fact that mutation frequency of the SDHD gene is less than that of allelic loss at chromosome11q, where the SDHD gene is located, this region may contain other candidate tumor-suppressor genes involved in pathogenesis of PCC/PGL. The tumor-suppressor gene Men1 located in 11q13 is responsible for multiple endocrine neoplasia type 1 (Men1). However, the involvement of the Men1 gene in tumorigenesis of sporadic PCC/PGL is yet to be determined. To understand the roles of the two tumor-suppressor genes and LOH on chromosome 11q in Chinese patients with sporadic PCC or PGL, we performed mutation detection of the SDHD and Men1 genes in tumors from 35 Chinese patients with PCC/PGL; we also did LOH analysis at chromosome 11q for 25 patients out of the 35. No mutation was found in all of 35 patients. However, LOH was detected at one or more loci in 11 of the 25 (44%) tumor samples. The highest frequency of LOH occurred at D11S2006 (41%). Our results suggested that mutation in SDHD or Men1 gene was not found in Chinese patients with sporadic PCC/PGL. However the loss of chromosome 11q might be critical in development of PCC or PGL.