The clinical outcome of prospective screening for multiple endocrine neoplasia type 2a. An 18-year experience

Cytogenetics and the surgeon: an invaluable tool in diagnosis, prognosis and counselling of patients with solid tumours

BACKGROUND

Cytogenetic studies have become an important part of tumour characterization. In a minority of tumours cytogenetic and/or molecular studies may be of help for diagnosis, selection of treatment protocols and predicting outcome.

METHODS

This article reviews the literature on solid tumour translocations and established family cancer syndromes. In addition, the potential importance of genetics in management of patients with breast, ovarian and pancreatic carcinoma is reviewed.

RESULTS AND CONCLUSION

Cytogenetic analysis of tumours may help confirm the diagnosis when conventional histology demonstrates no evidence of differentiation along a particular tissue pathway. For patients with well defined cancer syndromes, cytogenetic and molecular analysis offers the prospect of screening to reduce the risk of malignant disease. For many malignancies the underlying genetic anomalies are gradually being elucidated. Further studies designed to demonstrate the significance of these findings can only be undertaken if tumour material is collected and stored in optimal conditions for cytogenetic and/or molecular biological studies.

The ret-Activating Ligand GDNF Is Differentiative and Not Mitogenic for Normal and Neoplastic Human Chromaffin Cells In Vitro

Activating mutations of the receptor tyrosine kinase, ret, are associated with multiple endocrine neoplasia type 2A (MEN 2A). However, the mechanisms leading to tumor development are unclear. Glial-derived neurotrophic factor (GDNF) activates wild-type ret via interaction with a second receptor, GFR a-l. We have utilized GDNF to stimulate normal and neoplastic chromaffin cells in order to ask whether ret activation is mitogenic. Cells from three normal adult adrenal medullas, one sporadic pheochromocytoma, and three MEN-2A pheochromocytomas were labeled with bromodeoxyuridine (BrdU) for 12 d in the presence or absence of GDNF or nerve growth factor (NGF), which is known to stimulate neurite outgrowth, but not proliferation in human chromaffin and pheochromocytoma cell cultures. Responses to GDNF and NGF were comparable, except for two MEN-2A pheochromocytomas that responded minimally to GDNF and robustly to NGF. These tumors responded to GDNF biochemically, as measured by phosphorylation of mitogen-activated protein kineses, despite their weak morphological responses. Our findings suggest that activation of ret may not be sufficient to produce chromaffin cell hyperplasia or neoplasia directly by stimulating cell proliferation. However the possibility that altered cell-cell or cell-substrate interactions might cause responses to become differ entiative rather than proliferative in vitro has not been ruled out. We also demonstrate, for the first time, that at least some human pheochromocytomas with an MEN-2A ret mutation respond to a normal ret ligand. This responsiveness could be mediated by a remaining normal ret allele or by other mechanisms.

False-positive results of basal and pentagastrin-stimulated calcitonin in non-gene carriers of multiple endocrine neoplasia type 2A

Direct DNA analysis permits accurate identification of gene carriers in kindred members with multiple endocrine neoplasia type 2A (MEN 2A). The aim of this study was to assess the specificity of basal and pentagastrin stimulated calcitonin levels in 3 family members with MEN 2A. For this purpose 53 members of 3 consecutive families with MEN 2A were evaluated in a university medical center. Serum calcitonin, basal and stimulated, was determined by a commercial RIA. RET protooncogene analysis was carried out by automatic DNA sequencing and adequate digestion of PCR amplified products for exons 10 and 11. Two distinct mutations in the RET protooncogene were identified. A T-->A transition at position 1783 (codon 618) in exon 10 was detected in one family, and a G-->A replacement at position 1832 (codon 634) in exon 11 in the others. In non-gene carriers we obtained 6.6% of false-positive results for basal calcitonin and 15.4% for the pentagastrin provocative test. We conclude that the specificity of basal and pentagastrin-stimulated calcitonin is rather limited and RET protooncogene analysis must be the first line screening procedure in order to identify gene carriers.

Mutation of RET codon 768 is associated with the FMTC phenotype

Multiple endocrine neoplasia type 2A (MEN 2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC) are inherited cancer syndromes resulting from mutations in the RET proto-oncogene. Missense mutations of five codons in exons 10 and 11 are found in both MEN 2A and FMTC families, while mutations at codon 768 in exon 13 have been identified in three FMTC families. We report here the results of mutation analysis on a large multi-generation family with multiple cases of medullary thyroid carcinoma (MTC) or C-cell hyperplasia and two individuals with isolated adrenal medullary hyperplasia. A mutation in exon 13, which alters codon 768 from a GAG (Glu) to a GAC (Asp), was found to segregate with the FMTC phenotype in this family but not with the adrenal medullary hyperplasia. These findings suggest that the codon 768 mutation does not predispose to adrenal medullary hyperplasia, but is an accurate predictor of the MTC phenotype in this family.

Composite pheochromocytoma/ganglioneuroma of the adrenal gland associated with multiple endocrine neoplasia 2A: case report with immunohistochemical analysis

We report a case of composite pheochromocytoma/ganglioneuroma arising in a background of diffuse and nodular medullary hyperplasia in the adrenal gland of a 34-year-old man with multiple endocrine neoplasia 2a (MEN 2a). Cells were histologically classified as chromaffin or chromaffin-like (small typical-appearing pheochromocytoma cells), neuron-like (possessing ganglion cell morphology), and intermediate. We speculate that these cell types may represent a spectrum of differentiation of a neoplastic clone, with the intermediate cells representing a transitional stage between chromaffin cells and neurons. All three cell types in the composite tumor and all chromaffin cells in both nodular and nonnodular areas of the remaining medulla were strongly immunoreactive for tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis. In contrast, neuron-like cells (and to a variable extent intermediate cells) displayed selective loss of expression of phenylethanolamine-N-methyltransferase (PNMT), the enzyme that synthesizes epinephrine. Proliferative activity of the composite tumor and both the nodular and nonnodular medulla was studied by staining for the endogenous cell proliferation antigen Ki-67, using monoclonal antibody MIB-1. MIB-1 labeling was highest in Schwann cell areas of the composite tumor, followed by chromaffin-like cells in the composite tumor and in the separate nodules. Labeling was absent in neuron-like cells, consistent with the cells' postulated status as terminally differentiated derivatives of a chromaffin cell precursor, and was highly variable in nonnodular areas of the medulla. The latter observation suggests topographical variation in signals that drive chromaffin cell proliferation in MEN.

Multiple endocrine neoplasia type II and familial medullary thyroid carcinoma. Impact of genetic screening on management

The identification of ret protooncogene mutations in MEN-II and Hirschsprung disease has not only improved the clinical management of these genetic conditions but has also provided important information regarding mechanisms of transformation and neural crest development. An indication of how neural-crest cells migrate during embryonic life and the key processes involved in their differentiation now seems within reach. The continued pace of scientific discovery suggests that our understanding of and ability to prevent or treat hereditary and sporadic forms of MTC will continue to improve.

Cortical-sparing adrenalectomy for patients with bilateral pheochromocytoma

BACKGROUND

Bilateral pheochromocytomas are common in patients with multiple endocrine neoplasia type 2 (MEN 2) and von Hippel-Lindau disease (VHL). In an effort to avoid long-term steroid dependence and Addisonian crisis, we have performed cortical-sparing adrenalectomy in this patient population.

METHODS

Retrospective chart review was completed for patients with MEN 2- or VHL-related pheochromocytomas who underwent laparotomy at our institution for intended cortical-sparing adrenalectomy between June 1965 and March 1995.

RESULTS

Fifteen patients (MEN 2A [10], MEN 2B [2], VHL [3]) underwent laparotomy for cortical-sparing adrenalectomy. None of the tumors were malignant. Cortical-sparing adrenalectomy was possible in 14 (93%). Thirteen of these 14 patients (93%) had normal postoperative plasma cortisol measurements and did not require steroid hormone supplementation. At a median follow-up of 138 months, two patients had died of metastatic medullary thyroid cancer, no patient had suffered Addisonian crisis, and three patients (21%) had recurrent pheochromocytomas (at 118, 176, and 324 months after operation). The remaining nine patients were alive without pheochromocytomas.

CONCLUSIONS

Cortical-sparing adrenalectomy can be performed successfully in MEN 2 or VHL patients with bilateral pheochromocytomas, avoiding chronic steroid hormone replacement and the risk of Addisonian crisis in most patients. Long-term follow-up is necessary because recurrence may develop many years after operation.

Application of genetic screening information to the management of medullary thyroid carcinoma and multiple endocrine neoplasia type 2

Application of RET proto-oncogene mutation analysis to the clinical management of MEN 2 and FMTC has simplified and enhanced the power of earlier used screening and treatment efforts for hereditary MTC. The approaches outlined herein are cost-effective, have improved diagnostic accuracy, and hold the promise of improved cure rates for this neoplasm. Further studies to elucidate the mechanism by which these activating mutations cause transformation may lead to other strategies for prevention or treatment of this neoplasm.

Diagnosis of multiple endocrine neoplasia [MEN] 2A, 2B and familial medullary thyroid cancer [FMTC] by multiplex PCR and heteroduplex analyses of RET proto-oncogene mutations

Multiple endocrine neoplasia type 2 [MEN 2] is an autosomal dominant cancer syndrome with two subtypes, 2A and 2B. MEN 2A and medullary thyroid cancer [MTC] are caused by > 25 different point mutations in exons 10, 11, and 13 of the RET proto-oncogene, whereas MEN 2B is caused by a single exon 16-point mutation. Various molecular methods have been used to identify the different mutations, including DNA sequencing, restriction enzymatic analyses, chemical cleavage mismatch, Single Stranded Conformational Polymorphism [SSCP], and Denaturing Gradient Gel Electrophoresis [DGGE]. These techniques, although useful and accurate, are labor intensive and some involve the use of radioactivity. We have developed a multiplex PCR assay simultaneously to amplify exons 10, 11, and 13 of the RET proto-oncogene. The multiplex PCR product is then analyzed on a modified Mutation Detection Enhancement [MDE] matrix for heteroduplex identification and visualized with ethidium bromide. Distinct heteroduplexes were detected for each known RET proto-oncogene mutation available in our laboratory (nine in exon 10, five in exon 11, one in exon 13, and the single exon 16 mutation). Presymptomatic DNA diagnosis of MEN 2 is essential since pentagastrin-stimulated calcitonin studies can occasionally produce false positive results and lead to unnecessary thyroidectomies. Prophylactic thyroidectomy is recommended by age 5 or 6 once a mutation is identified in a patient, since penetrance is very high. MDE heteroduplex detection provides a quick, efficient, and inexpensive method of screening for RET mutations in MTC patients with unknown mutations, or for presymptomatic diagnosis in individuals at risk for inheriting a known RET mutation. Confirmation of the specific mutation can be achieved by restriction enzymatic digestion (if feasible) or by DNA sequencing.

Presymptomatic DNA screening in families with multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma

BACKGROUND

Missense mutations of the ret proto-oncogene on chromosome 10q11.2 are the underlying cause of hereditary medullary thyroid carcinoma (MTC), either as familial MTC only (FMTC) or as a part of multiple endocrine neoplasia type 2 syndrome (MEN 2). This study presents our experience with direct presymptomatic DNA screening in MEN 2 and FMTC kindreds.

METHODS

Twenty one families with MEN 2 or FMTC were considered in the study. One hundred three individuals had been analyzed; 56 were at risk. The ret mutations were detected by DNA analysis of exons 10, 11, and 16 by using nonradioactive labeling method based on digoxigenin DNA sequencing technique. Serum calcitonin evaluation was carried out in all individuals at risk. Thyroidectomy was performed in those who had to undergo surgery.

RESULTS

The ret mutations were identified in all 21 families. In MEN 2A and FMTC families mutations occurred in exons 10 and 11. MEN 2B families had mutations in exon 16. The most frequent mutation in MEN 2A and FMTC affected codon 634. Twenty one gene carriers were identified in unaffected individuals at risk. Ten of 21 gene carriers had elevated calcitonin levels, and 11 had normal levels. MTC or C-cell hyperplasia was found in six gene carriers with pathologic calcitonin values who underwent operation. In a 5-year-old gene carrier with normal calcitonin values C-cell hyperplasia was evident.

CONCLUSIONS

Direct predictive DNA analysis allows us to identify MEN 2 or FMTC gene carriers and offer them prophylactic treatment.

Clinical use of molecular information in the management of multiple endocrine neoplasia type 2A

One hundred and ninety-seven members of 28 kindreds with multiple endocrine neoplasia type 2A (MEN 2A) were screened for RET proto-oncogene exon 10 and 11 mutations. Seventy-one known affected individuals had mutations of codons 609, 618, 620 or 634, whereas 53 unaffected individuals had no abnormalities. Nineteen out of 54 individuals of unknown status, mostly children, had RET mutations. Four of these children had thyroidectomy based on this analysis and were found to have C-cell abnormalities. We identified one false negative mutation analysis because of a codon 691 polymorphism. We conclude that RET mutational analysis is a cost-effective and accurate method for determination of gene carrier status in MEN 2A.

From medical history and biochemical tests to presymptomatic treatment in a large MEN 2A family

An extensive study was published in 1959 in the Netherlands on a large family, which initially attracted attention because of a family history of attacks of shaking. Clinical investigation revealed phaeochromocytomas in four family members. In 1975, the family was identified to be a MEN 2A family, and since then, the members were examined annually using measurement of catecholamine metabolites in 24-h excreted urine and C-cell stimulation tests. In 1993, the RET proto-oncogene on chromosome 10q11 was found to be associated with MEN 2A and a specific mutation in this gene was identified in the family. In this family, 32 MEN 2A patients were detected. Since screening started in 1975, no patient died of phaeochromocytoma; however, two patients died of metastasized medullary thyroid carcinoma (MTC) (mean age 46 years). Twelve patients were operated on for phaeochromocytoma, and 13 for MTC. The results of DNA-analysis revealed the failures of the biochemical tests to identify affected family members. Six disease gene carriers with normal C-cell stimulation test results appeared to have small multifocal MTCs. Two carriers with normal excretion levels of catecholamines had a small phaeochromocytoma. DNA-analysis enables the unambiguous diagnosis of MEN 2A gene carrier-ship, allowing presymptomatic surgery for MTC.

Pheochromocytoma in multiple endocrine neoplasia type 2: European study. The Euromen Study Group

OBJECTIVES

Pheochromocytoma (pheo) is the second component of the multiple endocrine neoplasia type 2 (MEN 2) syndrome. Clinical expression is sometimes poor, and chronology between medullary thyroid carcinoma (MTC) and pheo is not well evaluated. Therefore, a retrospective study was done in eight European countries in order to precise the main characteristics of pheo in MEN 2.

SUBJECTS

Data from 300 MEN 2 patients with pheo (274 MEN 2 A and 26 MEN 2 B) were obtained from cases registered by the EuroMen study group, and collected by a medical standardized questionnaire. These cases occurred between 1969 and 1992.

RESULTS

Mean age at diagnosis of pheo was 39.5 years (range 14-68 years) in MEN 2A and 32.4 years (range 15-41 years) in MEN 2B patients. Pheo occurred first in 25.1% of the cases (2-15 years before diagnosis of MTC) and after MTC in 40.2% (2-11 years). In other cases (34.7%), MTC and pheo were diagnosed at the same time. Involvement was bilateral in 67.8% of cases. Malignancy was only 4%. Thirty-nine deaths occurred in these 300 patients, 64.1% were linked in pheo, 23.1% to MTC and 12.8% to other causes. Surgery was unilateral in 39.7% of the cases and bilateral adrenalectomy was the first procedure in 48.4%. A bilateral adrenalectomy in two steps had to be done in 11.9% of cases. In conclusion, these results justify systematic and prolonged biochemical screening of pheo during follow-up of MTC and address some questions about the best mode of surgery.

Primary hyperparathyroidism in multiple endocrine neoplasia type 2A

The rarity of primary hyperparathyroidism (PHPT) in multiple endocrine neoplasia type 2A (MEN 2A) led us to study clinical findings, surgical therapy and outcome in 67 patients in order to evaluate our therapeutic strategy. The retrospective study was based on cases registered by the EUROMEN study group (nine participating centres) from 1972 to 1993. Characteristics of PHPT in 67 patients (41 females, 26 males) with MEN 2A were reviewed. All patients underwent exploratory neck surgery; PHPT was confirmed histologically and/or biochemically. The median age at diagnosis of PHPT was 38 years. In 75% of the patients, PHPT and medullary thyroid carcinoma were diagnosed synchronously, while in 4%. PHT was diagnosed earlier. In 18% of the patients, PHPT was diagnosed after thyroidectomy, and in 3%, after discovery of pheochromocytoma. Primary hyperparathyroidism was asymptomatic in 84% of the patients; 15% suffered from renal stones. Serum calcium was slightly elevated in 69% (2.9 +/- 0.2 mmol-1) and normal in 16% of subjects. A single adenomectomy was performed in 42% of the patients, subtotal parathyroidectomy in 31% and total parathyroidectomy with autotransplantation in 16%. Independent from the extent of resection, cure was achieved in 94% of the patients, including 13% with hypoparathyroidism; hypercalcaemia persisted in 3% and no information was available in 3%. In an 8-year follow-up, hypercalcaemia recurred in 12% of the patients, although half had undergone parathyroidectomy totally or subtotally. CONCLUSION. MEN 2A-related PHPT is characterized by a mild hypercalcemia which is mostly asymptomatic and can be cured by simple resection of an enlarged parathyroid gland in most cases.

Medullary thyroid carcinoma: recent advances and management update

Medullary thyroid carcinoma (MTC) is a malignancy of the thyroid C-cells that comprises 5-10% of all thyroid cancers. MTC occurs in both sporadic and familial forms, the latter making up 25% of all MTCs and being comprised of three distinct syndromes--multiple endocrine neoplasia type 2A (MEN 2A), multiple endocrine neoplasia type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). To date, screening for MTC has been performed using the pentagastrin stimulation test, which is a provocative test for calcitonin release. Germline mutations in the RET protooncogene have been identified in families manifesting these syndromes and genetic screening of individuals at risk of one of these syndromes has become integral to their clinical management. The majority of the mutations associated with MEN 2A and FMTC are tightly clustered in a cysteine-rich region of the RET receptor. A single mutation associated with MEN 2B is in the the tyrosine kinase domain of the RET receptor. Somatic mutations have been identified in the tumor tissue of individuals with sporadic MTC and may prove to be helpful markers in discerning the hereditary or sporadic nature of the MTC. There is general agreement that the primary operation for MTC should include total thyroidectomy and central neck lymph node clearance. The role of microdissection for recurrent disease awaits longitudinal evaluation. External radiotherapy, radionuclide therapy, and chemotherapy may have a role in palliation, but have not been proven to have a curative value. Prognostic factors are discussed.

The practical management of multiple endocrine neoplasia

Adbances in the identification and localization of the abnormal genes in the multiple endocrine neoplasia syndromes have provided new methods of identifying "at risk" individuals in these families. Genetic testing using linkage analysis in multiple endocrine neoplasia (MEN) 1 and direct mutation analysis of the RET protooncogene in MEN 2 is now available for these disorders. New management issues for these disorders have resulted, and a practical approach to these issues is discussed.

Screening for cancer in high risk families

OBJECTIVE

To review screening for cancer in high risk families.

METHODS AND RESULTS

Screening for hereditary cancer involves three steps: it is first necessary to identify families at high risk by examining the number and sites of cancer in a family. Special attention is given to cancers appearing at an early age, to unusual sites, and multiple primary cancers. Second, a molecular diagnostic test is performed in order to identify family members who carry a mutant copy of the suspected gene. DNA-based diagnostic testing is now available for hereditary breast-ovarian cancer, for hereditary nonpolyposis colon cancer, for Gardner syndrome (familial polyposis coli), for neurofibromatosis, multiple endocrine neoplasia, and for Von-Hippel Lindau disease. Third, individuals found to carry susceptibility genes are offered screening for the early detection of tumours. Some screening methods are in conventional use (e.g., colonoscopy and mammography); others are reserved for the investigation of familial cancers (e.g., pentagastrin challenge test).

CONCLUSION

A comprehensive clinic for hereditary cancer must consider all three phases of the screening program and will provide expert genetic counselling to family members involved in the process.

RET proto-oncogene mutations in multiple endocrine neoplasia type 2 and medullary thyroid carcinoma

The identification of RET proto-oncogene mutations in patients with MEN2 2 years ago was a watershed event in the management of this genetic cancer syndrome. The identification of a finite number of mutations that together causes more than 95% of hereditary and 15-25% of sporadic MTC has made it possible to develop simple and definitive tests to screen individuals at risk for this tumour syndrome. The impact of this technology is enormous. It is now possible to reassure 50% of family members at risk that they, and their children, do not have to worry about developing MTC. In the other 50% who are gene carriers, it is now possible to approach clinical management with greater certainty and plot strategies that are likely to result in a greater percentage of curative therapy. It seems likely that this technology will also have an impact on the management of sporadic MTC, although it is still too early to define a specific role for mutational analysis in these patients, except to exclude hereditary disease. The identification of specific mutations causative for MTC makes it possible to conceive future strategies for the treatment or prevention of MTC and to further extend the impact of these exciting findings.

Presymptomatic genetic screening in families with multiple endocrine neoplasia type 2

Medullary thyroid carcinoma occurs sporadically or as a part of the inherited cancer syndrome multiple endocrine neoplasia (MEN) type 2. The MEN 2 gene has been identified as the RET proto-oncogene on chromosome 10. In MEN 2A, RET mutations are detectable in one of five cysteine codons within exons 10 and 11 and in MEN 2B in codon 918 (exon 16). Direct DNA testing for RET proto-oncogene mutations is the method of first choice in presymptomatic screening of MEN 2 families. Gene carriers should be offered prophylactic thyroidectomy. The process of DNA analysis for RET proto-oncogene mutations is demonstrated in one family with hereditary medullary thyroid carcinoma. RET mutations were detectable in five of the nine family members at risk.

Molecular genetics of thyroid and parathyroid neoplasia

There have been several recent advances in the understanding of the process of carcinogenesis in the thyroid and parathyroid glands. The specific abnormal molecules are, in many instances, well understood. This review provides an overview of the molecules in the cell that regulate cell growth and proliferation and identifies the molecules that have been found to be abnormal (or mutant) in various types of thyroid and parathyroid neoplasia.

Pheochromocytoma. Update on diagnosis, localization, and management

Pheochromocytoma, although rare, is associated with a high degree of morbidity and mortality if not recognized. A high degree of suspicion in patients with new-onset hypertension; hypertension with sudden worsening or development of diabetes mellitus; or a family history of MEN, neuroectodermal tumors, or simple pheochromocytoma should prompt biochemical confirmation with either 24-hour urine catecholamines (norepinephrine and epinephrine) or total MET (NMET plus MET). Following confirmation of the diagnosis, radiologic studies with CT and (if needed) MIBG are employed to localize the tumor. Surgical removal is the only definitive therapy. Medical management with alpha-blocking agents, to control symptoms and prevent a hypertensive crisis, is generally advocated for 2 weeks preoperatively and intraoperatively. Occasionally, beta-blockers, employed only after adequate alpha-blockade, are necessary to control tachycardia and tachyarrhythmias. High-dose MIBG and combination chemotherapy have been used adjunctively to treat malignant pheochromocytoma, although neither modality provides lasting satisfactory results. Normal urine assays performed 2 weeks postoperatively ensure the complete removal of all tumor. Additionally, lifelong follow-up (yearly initially) is necessary to detect any signs of benign recurrence or malignancy because these have been reported to occur as long as 41 years after the initial surgical resection. Biochemical evidence of excess catecholamine production usually precedes the clinical manifestations of catecholamine excess when these tumors recur.

Clinical screening as compared with DNA analysis in families with multiple endocrine neoplasia type 2A

BACKGROUND

Multiple endocrine neoplasia type 2A (MEN-2A) is characterized by medullary thyroid carcinoma in combination with pheochromocytoma and sometimes parathyroid adenoma. Missense mutations in the RET proto-oncogene are associated with MEN-2A. Their detection by DNA analysis allows the identification of carriers of the gene, in whom the risk of medullary thyroid carcinoma is 100 percent. We compared the reliability of biochemical tests with that of DNA analysis in identifying carriers of the MEN2A gene.

METHODS

Starting in 1975, we screened 300 subjects in four large families with MEN-2A for expression of the disease, using measurements of plasma calcitonin after stimulation with pentagastrin or calcium and urinary excretion of catecholamines and catecholamine metabolites. We tested for carrier status by DNA analysis, including linkage analysis, and more recently by analysis of mutations in the RET gene.

RESULTS

Of 80 MEN2A gene carriers (in 61 of whom carrier status was proved by DNA analysis), 66 had abnormal plasma calcitonin values and medullary thyroid carcinoma. Fourteen young carriers had normal results of plasma calcitonin tests. In 8 of these 14, thyroidectomy revealed small foci of medullary thyroid carcinoma; the remaining 6 have not yet been operated on. Of the other 220 family members, 68 were found by DNA analysis not to carry the MEN2A gene. None of these 68 subjects had medullary thyroid carcinoma or pheochromocytoma; 6 had elevated plasma calcitonin concentrations and underwent thyroidectomy but had only C-cell hyperplasia.

CONCLUSIONS

Unlike biochemical tests, DNA analysis permits the unambiguous identification of MEN2A gene carriers.

Case report: bilateral adrenal pheochromocytoma

Pheochromocytoma remains a clinical challenge to diagnose and manage. In addition, the association of multiple endocrine neoplasia syndromes with pheochromocytoma require the clinician's awareness to evaluate patients with pheochromocytoma (especially when bilateral) for abnormalities in thyroidal C-cell function with serum calcitonin determinations. The authors present a case of a 42-year-old woman initially diagnosed with, and treated for, cranial artery vasculitis because she had a stroke and a history of rheumatoid arthritis and asthma. Subsequent evaluation of episodic blood pressure increases, headache, and tachycardia revealed biochemical evidence of catecholamine overproduction. Bilateral adrenal masses were found on computed tomography scanning, and the functional nature of the adrenal masses was confirmed by a meta-Iodobenzylguanidine scan. Upon further evaluation, an elevated serum calcitonin concentration was demonstrated, which increased greatly with pentagastrin stimulation. C-cell hyperplasia was demonstrated by subsequent thyroidectomy, confirming the diagnosis of multiple endocrine neoplasia 2A. The difficulty in arriving at a correct diagnosis, the subsequent management, including bilateral adrenalectomy and thyroidectomy, and newer insight into the genetic abnormalities of multiple endocrine neoplasia 2A are discussed.

Presymptomatic screening for medullary thyroid carcinoma in patients with multiple endocrine neoplasia type 2A

Presymptomatic screening of medullary thyroid carcinoma in MEN IIA families enables the early diagnosis of this tumor with its significant morbidity. Biochemical screening consists of basal and stimulated serum calcitonin evaluation. Genetic screening is based on DNA analysis using linked DNA markers. Thyroidectomy at an occult tumor stage may be curative. Calcitonin measurement was carried out in 58 apparently unaffected family members at risk and 11 MEN IIA patients. Calcitonin elevation was detected in nine individuals. All nine underwent thyroidectomy. Histologic examination confirmed medullary thyroid carcinoma in eight patients and in one case C cell hyperplasia. Postoperatively, eight patients (89%) are clinically and biochemically tumor-free (mean follow-up 30 months). DNA screening results in one affected family are presented. DNA analysis allowed recognition of one apparently unaffected individual at risk as a MEN IIA gene carrier. One family member at risk was found not to carry the gene and may be excluded from further screening.

The gene causing multiple endocrine neoplasia type 2 (MEN 2)

Multiple endocrine neoplasia (MEN) types 1 and 2 are distinct dominantly inherited syndromes of cancer predisposition in man. MEN 1 involves the parathyroids, pituitary, and pancreatic islets; MEN 2 involves the thyroid C-cells, adrenal medulla and parathyroids. In some varieties of MEN 2 there are also developmental abnormalities of the autonomic nervous system of the gut. The MEN 1 predisposing gene has been mapped by linkage to chromosome 11q13, and it is likely that the gene will shortly be identified by positional cloning. The predisposing gene for MEN 2 has been shown to be the receptor tyrosine kinase ret. Mutations in different domains of ret are responsible for the different combinations of phenotypes seen in distinct clinical varieties of MEN 2 and in Hirschsprung disease.

Screening for adrenal medullary disease in patients with medullary thyroid carcinoma

Adrenal medullary disease (AMD) is clinically silent in most patients with medullary thyroid carcinoma (MTC). It was screened yearly by urinary measurements of catecholamines and derivates, and by abdominal ultrasonography (US) in a series of 174 patients with MTC. In cases with suspicion of AMD, abdominal computerized tomography and scintigraphy with meta-iodobenzylguanidine were also performed. AMD was discovered in 10 patients (one adrenal medullary hyperplasia and 9 pheochromocytomas). Three patients were already known to belong to a type II multiple endocrine neoplasia (MEN-2a) family and two had a MEN-2b syndrome. In 5 patients previously considered as having either a sporadic (4 cases) or a familial type of isolated MTC (one case), the occurrence of AMD led to diagnose a MEN-2a syndrome. The diagnostic values of the tests were evaluated by a case-control study. Urinary metanephrine plus normetanephrine (MN+N) had an acceptable sensitivity (0.8) and specificity (0.8). The other urinary tests had a high specificity (range: 0.8 to 1) but a poor sensitivity (range: 0.1 to 0.5). US had a high sensitivity (0.8) and a specificity of one. MN+N and US performed yearly constitute a simple and efficient strategy to screen for AMD in patients with MTC.

Magnetic resonance imaging or metaiodobenzylguanidine scintigraphy for the demonstration of paragangliomas? Correlations and disparities

Paragangliomas are tumours arising from paraganglionic tissue dispersed from the base of the skull to the pelvic diaphragm. These tumours produce symptoms by secreting catecholamines (functioning tumours) or by local tumour expansion. They can be part of several hereditary disorders. The introduction of magnetic resonance (MR) imaging and metaiodobenzylguanidine (MIBG) scintigraphy has provided new insights into paragangliomas and has tremendously changed the topographic diagnosis of paragangliomas. Both techniques have proven to be adequate in localising paragangliomas. In this report, the performance of these two noninvasive imaging methods in the examination of paragangliomas is compared and the merits and deficits of the two techniques are discussed. Both techniques produce comparable results in the detection of functioning paragangliomas. MR imaging, however, also demonstrates tumours that do not take up MIBG. MR imaging does not involve the use of ionising radiation and is not hampered by medication. Moreover, MR imaging has a higher spatial resolution. Because of these merits it is concluded that for demonstration of paragangliomas, whole-body MR imaging is the preferred and initial method of investigation. MIBG scintigraphy, on the other hand, continues to be a reliable method for non-invasive detection of functioning paragangliomas. At present it is clearly faster in whole-body imaging than MRI and it is definitely patient-friendly (no claustrophobia). It could be reserved for cases where a strong suspicion of a functioning paraganglioma persists, despite normal MR imaging findings, and for cases where doubt exists about the functional activity of one or more multicentric tumours. MIBG scintigraphy must be used in the evaluation of patients referred for iodine-131 MIBG treatment.

Specific mutations of the RET proto-oncogene are related to disease phenotype in MEN 2A and FMTC

We have analysed 118 families with inherited medullary thyroid carcinoma (MTC) for mutations of the RET proto-oncogene. These included cases of multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial MTC (FMTC). Mutations at one of 5 cysteines in the extracellular domain were found in 97% of patients with MEN 2A and 86% with FMTC but not in MEN 2B patients or normal controls. 84% of the MEN2A mutations affected codon 634. MEN 2A patients with a Cys634 to Arg substitution had a greater risk of developing parathyroid disease than those with other codon 634 mutations. Our data show a strong correlation between disease phenotype and the nature and position of the RET mutation, suggesting that a simple, constitutive activation of the RET tyrosine kinase is unlikely to explain the events leading to MEN 2A and FMTC.

Screening and surgical intervention in the multiple endocrine neoplasia patient

Persons with multiple endocrine neoplasias (MEN) are a unique group of patients that present with various APUDomas. Screening of family members can lead to early detection of these tumors and possible cure of potentially fatal tumors. Screening for the MEN syndromes at present is limited to provocative and biochemical parameters. The gene(s) responsible for these syndromes have not, as of yet, been characterized but in the future will add greatly to the ability to identify these patients early. Early surgical intervention of these APUDomas, has lead to an improved prognosis for these tumors. The screening and the surgical approach to each syndrome are outlined.

The relationship between serum calcitonin and calcium in the hemodialysis patient

An increase in the serum calcium level is known to stimulate calcitonin secretion, but whether calcitonin contributes to calcium regulation in the dialysis patient is not known. Because we recently observed in the rat that (1) a sigmoidal calcitonin-calcium curve was present, and (2) calcitonin stimulation decreased the calcemic response to parathyroid hormone (PTH), the relationship between serum calcitonin and calcium was studied in six hemodialysis patients. To evaluate both the calcitonin-calcium and PTH-calcium relationships, hemodialysis with a low-calcium dialysate (2 mg/dL) was performed and followed 1 week later by hemodialysis with a high-calcium dialysate (8 mg/dL). The calcitonin-calcium relationship was best represented as a sigmoidal curve that was opposite in direction to the PTH-calcium curve. The range of the calcitonin-calcium curve was less than the PTH-calcium curve; as a percent of maximal, the minimal calcitonin was higher than the minimal PTH, 61% +/- 5% versus 26% +/- 4% (P < 0.001). As opposed to the PTH-calcium curve in which the basal PTH value was intermediate between the minimal and maximal PTH, the basal calcitonin value was close to the minimal calcitonin. Despite a wide range of ionized serum calcium concentrations (3.5 to 5.3 mg/dL), maximal stimulation was greater than maximal inhibition of calcitonin, 60% +/- 13% versus 3% +/- 2% (P = 0.01). Finally, a significant correlation was observed between basal and maximal calcitonin (r = 0.99, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

A new polymorphic marker (D10S97) tightly linked to the multiple endocrine neoplasia type 2A (MEN2A) locus

Familial multiple endocrine neoplasia type 2A (MEN 2A) is a cancer syndrome that is inherited as an autosomal dominant with high penetrance. Its clinical features are medullary carcinoma of the thyroid, pheochromocytomas, and hyperparathyroidism. A new polymorphic locus D10S97 (probe: KW6 delta SacI) detects a codominant EcoRI polymorphism that is tightly linked to the MEN2A locus. The peak lod score for linkage between D10S97 with MEN2A is 13.03 at theta = 0.00. The polymorphic locus D10S97 maps, by linkage analysis, into the previously defined interval between FNRB and RBP3 to which MEN2A has been assigned. We present physical mapping data showing that the probe pKW6 originates from 10p13 and that the polymorphic locus D10S97 in 10q11.2 is detected by cross-hybridization.

Early diagnosis of the multiple endocrine neoplasia type 2 syndrome: consensus statement. European Community Concerted Action: Medullary Thyroid Carcinoma

The diagnosis of medullary thyroid carcinoma by biochemical and genetic testing is possible in families with multiple endocrine neoplasia type 2. At an early stage total thyroidectomy usually cures the patient. As the clinical penetrance of the autosomal dominant, transmitted, multiple endocrine neoplasia type 2 gene is not complete, family screening is indicated for every new patient who presents with apparently sporadic medullary thyroid carcinoma. Problems related to a screening programme and early diagnosis have led the members of the European Community Concerted Action: Medullary Thyroid Carcinoma group to formulate a consensus on biochemical and genetic screening. For biochemical screening, measurement of basal and pentagastrin and/or calcium stimulated serum levels of calcitonin by radioimmunoassay are essential starting at the age of three and continuing annually until 35 years of age. Furthermore, annual screening for pheochromocytoma by measuring the urinary excretion of catecholamines and for hyperparathyroidism by serum calcium determination is indicated. Genetic screening using linked markers can be done with a 95% accuracy in informative families when DNA is available from at least two family members proven to be affected. Biochemical screening can thus be reserved for gene carriers, while those at low risk can be reassured. Combined biochemical and genetic screening for multiple endocrine neoplasia type 2 is important and effective for the cure of medullary thyroid carcinoma.

Prediction of affected MEN2A gene carriers by DNA linkage analysis for early total thyroidectomy: a progress in clinical screening program for children with hereditary cancer syndrome

The gene predisposing to multiple endocrine neoplasia type 2A (MEN 2A) has been assigned to chromosome 10, and affected gene carriers can be identified before the development of associated malignancy in some informative families. We applied these advances in gene mapping to clinical screening for possible pediatric surgery. A family with MEN 2A, consisting of 88 members and their spouses, was studied to test the reliability of the provocation of plasma calcitonin with pentagastrin and the possibility of DNA diagnosis of mutated gene carriers with DNA probes closely linked to the MEN2A gene including RBP3 and FNRB genes. Nineteen of the 88 were diagnosed as MEN 2A carriers. Twelve of them were treated surgically and the others died of medullay thyroid carcinoma (MTC) or pheochromocytoma. A strikingly sensitive response of calcitonin was observed in all those with MTC. The genotypes cosegregating with the abnormal allele at MEN2A in this family could be deduced from clinically established affected members. The early detection of gene carriers allows us to concentrate our screening efforts on children at high risk and to release non gene carriers from repeated unnecessary testing. MEN2A is one of the first cancer syndromes for which DNA screening permits early detection of members at high risk.