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

Thyroid cancer in children

In 1996, the authors were asked to review the subject of thyroid cancer in children. Over the subsequent decade, much has been learned about the treatment and outcome of these uncommon tumors. We now recognize quantitative and perhaps qualitative differences in genetic mutations and growth factor expression patterns in childhood thyroid cancers compared with those of adults. We also know that thyroid cancers induce a robust immune response in children that might contribute to their longevity. Patients under 10 years of age probably represent a unique subset of children at particularly high risk for persistent or recurrent disease; the management of these patients is under evaluation. We remain limited in our knowledge of how to stratify children into low- and high-risk categories for appropriate long-term follow-up and in our knowledge of how to treat children who have detectable serum thyroglobulin but negative imaging studies. In this article, the authors update our understanding of thyroid cancers in children with special emphasis on how these data relate to the current guidelines for management of thyroid cancer developed by the American Thyroid Association Taskforce. The limited data regarding management of children who have detectable serum thyroglobulin but negative whole-body scans are also reviewed.

Thyroid cancer review 3: management of medullary and undifferentiated thyroid cancer

This is the last of the three review articles dealing with thyroid cancer. Over 90% of thyroid cancer is of the differentiated type associated with a very good 10-year disease-free survival rate. In contrast, the rare forms of thyroid cancer which comprise medullary thyroid cancer arising from parafollicluar C cells, Hurthle cell carcinoma, anaplastic carcinoma, thyroid lymphoma and squamous cell carcinoma are typically associated with a poorer survival rate. Management is based upon small retrospective cohort studies.

Diagnosis and management of medullary thyroid carcinoma

Successful treatment of MTC depends heavily on early diagnosis and treatment. Often, this is not possible for sporadic MTC; however, genetic testing for hereditary MTC makes this possible if genetic carriers have surgery before C cells undergo malignant transformation. All patients who have MTC should be tested for RET mutations, including putative sporadic cases. The leukocytes of suspected carriers and sporadic MTC cases should be tested for MEN2-associated germ-line mutations by polymerase chain reaction amplification of the appropriate RET gene exons, including 10, 11,13, 14, 15, and 16 (see Table I). When a RET mutation is found, all first-degree relatives must be screened to determine which individuals carry the gene. If these exons are negative, the other 15 should be sequenced because a small risk of hereditary MTC remains if no germ-line mutation is found. The probability that a first-degree relative will inherit an autosomal dominant gene for MTC from an individual who has sporadic MTC in whom no germ-line mutation is found is 0.18% . Patients who have MEN2B or RET codon 883 or 918 mutation should have a total thyroidectomy within the first 6 months of life, preferably within the first month of life. Patients who have 634 mutations, which account for approximately 70% of all MTC mutations, should undergo thyroidectomy by age 5 years. The recommendations for the timing of prophylactic thyroidectomy are not consistent for the less common mutations (see Table 2). There is a balance between performing prophylactic thyroidectomy earlier than at the youngest age at with MTC has been reported to occur for a specific RET mutation (see Fig. 3 and Table 2) and the complications of thyroidectomy, including permanent hypoparathyroidism and laryngeal nerve damage. Preoperative measurement of plasma free metanephrine and neck ultrasonography always should be done if the diagnosis of MTC is known preoperatively. Initial treatment of MTC is total thyroidectomy, regardless of its genetic type or putative sporadic nature, because surgery offers the only chance for a cure. Treatment with 1311 has no place in the management of MTC. Plasma CT measurements provide an accurate estimate of tumor burden and are especially useful in identifying patients who have residual tumor. Pentagastrin- or calcium-stimulated plasma CT testing is useful in identifying CCH or early MTC in carriers of RET mutations that are associated with late onset MTC. Pheochromocytoma may occur before or after MTC and is an important cause of mortality, even in young patients. HPT is an important aspect of MEN2A and requires surgery according to current guidelines for the management of primary HPT. Early thyroidectomy and appropriate management of pheochromocytoma clearly have modified the course of this disease, but more research is necessary in kindreds who have rare MTC mutations. Moreover, new treatments for widespread MTC are necessary because current chemotherapy agents offer little benefit. New drugs that lock the action of tyrosine kinase offer some hope.

Genetic testing in endocrinology: lessons learned from experience with multiple endocrine neoplasia type 2 (MEN2)

Multiple endocrine neoplasia type 2 (MEN2) is a syndrome characterized by medullary thyroid carcinoma (MTC), unilateral or bilateral pheochromocytoma and hyperparathyroidism. Familial MTC (FMTC) is a subvariant of MEN2 in which affected individuals develop MTC without other manifestations of MEN2. The identification of RET proto-oncogene mutations in MEN2 and FMTC have provided a precise method for identifying gene carriers. This review provides a concise discussion of the use of genetic testing in the management of hereditary MTC, discussing the appropriate use of this new technology with an emphasis on early intervention to prevent death or serious morbidity from this disease.

Ret Germline Mutation In Codon 791 In A Family Representing 3 Generations From Age 5 To Age 70 Years: Should Thyroidectomy Be Performed?

OBJECTIVE

To describe a kindred with a rare RET germline mutation in codon 791 and discuss potential management strategies.

METHODS

We present clinical and biochemical data as well as results of mutation analysis in our study subjects and provide an overview of related published reports.

RESULTS

Multiple endocrine neoplasia type 2 (MEN 2) is a familial cancer syndrome characterized by the development of medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid hyperplasia or adenoma. Germline mutations in RET are responsible for this autosomal dominant syndrome. Familial MTC is a variant of MEN 2A and can be caused by RET mutations in codon 791. Deaths from gene carriers with mutations in these codons have not yet been reported. In general, gene carriers with these RET mutations have late-onset MTC. Because only a few kindreds with this specific mutation have been identified and no long-term follow-up data are available, management of these patients can be a challenge. We illustrate the difficulties with decisions about not only when to perform thyroidectomy in these patients but also whether thyroidectomy should even be considered in such gene carriers with a benign course. Our reported kindred included four carriers with a codon 791 RET germline mutation, one of whom had the rare concomitant occurrence of acromegaly and MEN 2A. The 70-year-old mother had acromegaly and hyperparathyroidism but normal serum calcitonin levels and normal findings on thyroid ultrasound examination. She refused pentagastrin testing and any surgical intervention. The 37-year-old daughter had hypothyroidism, a small thyroid gland, and negative results of pentagastrin stimulation testing of calcitonin. The 18-year-old grandson also had a negative pentagastrin test result and normal thyroid ultrasound findings. The 5-year-old granddaughter had normal results of thyroid ultrasonography. In all patients, we recommended thyroidectomy.

CONCLUSION

Prospective studies are needed to clarify which patients with codon 791 RET germline mutation should undergo thyroidectomy.

[Multiple endocrine neoplasias. Recent advances in clinical and genetic diagnosis]

PURPOSE

Multiple endocrine neoplasias (MEN) are autosomal dominant inherited syndromes characterized by the association of different glandular lesions in several members of the same kindred. The main clinical features of MEN 1 include primary hyperparathyroidism, pancreatic islet cell tumors and pituitary adenomas; less common features are adrenal adenomas, thymic and bronchial carcinoid tumors, lipomas and various cutaneous lesions. The MEN 2 syndromes (MEN 2A, MEN 2B and familial medullary thyroid carcinomas) are characterized by high penetrance of medullary thyroid carcinoma and differ in their variable expression of pheochromocytoma, hyperparathyroidism and other clinical features.

CURRENT KNOWLEDGE AND KEY POINTS

MEN 1 tumor suppressor gene encodes a nuclear protein, menin, which interacts with different regulation transcription factors. The MEN 2 syndromes are caused by germ-line mutations of the RET proto-oncogene, which encodes a transmembrane tyrosine kinase. Genetic testing for mutations in these 2 genes allows identification of individuals predisposed to the disease, early diagnosis, and clinical and therapeutic management.

FUTURE PROSPECTS AND PROJECTS

Fundamental approach will allow a best comprehension of physiopathogenic mechanisms of these disorders and the improvement of therapeutic management.

RET oncogene mutations in medullary thyroid carcinoma in Mexican families

BACKGROUND

Different RET oncogene mutations have been found to be associated with inherited medullary thyroid carcinoma (MTC) in the context of three different syndromes including multiple endocrine neoplasia types 2A (MEN 2A) and 2B (MEN 2B) and familial medullary thyroid carcinoma (FMTC). These mutations have been recorded in different populations, but to date there is no corresponding study in Mexican families. Our purpose was identification of RET mutations in Mexican families with inherited or sporadic MTC (SMTC) and search for RET protein expression as prognostic marker in MTC tumors.

METHODS

Nine unrelated families with MTC corresponding either to two MEN 2A, three MEN 2B, or four SMTC were studied. Screening of exons 10, 11, and 13-16 of RET oncogene in DNA from circulating lymphocytes and tumor samples were analyzed. Immuno- staining for RET was performed in the corresponding tumor.

RESULTS

Germline 918 ATG-->ACG RET mutation was present in three unrelated MEN 2B individuals and corresponding somatic mutation in one individual with SMTC; 634 TGC-->TTC RET mutation was detected in two related patients in an MEN 2A family and the 634 TGC-->TAC RET mutation was detected in 12 related individuals from a second MEN 2A family. RET protein expression was detected in all MTC tumors showing different staining intensity.

CONCLUSIONS

RET mutations found in Mexican patients with MTC are similar to those previously reported in several MTC families worldwide. This indicates that RET mutations are highly conserved and that MTC etiology does not depend to a great extent on environmental factors or ethnic differences. Detection of RET protein in MTC tissue sections is not useful as prognostic marker.

Providing information to patients with a rare cancer: using Internet discussion forums to address the needs of patients with medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare disease, and specific experience with the condition is not commonly found outside of major cancer centers. Because of the rarity and slow-growing natural history of the disease, patients with MTC frequently have many questions concerning prognosis, treatment, and follow-up care. Many of these patients have joined an e-mail group on the Internet through which they share information and concerns. The author has joined this group and shares her expert clinical knowledge about the disease. When individuals are armed with accurate and expert information, they can make informed decisions. The source of this information can be diverse. Nurses with expert knowledge can use opportunities such as e-mail groups to answer questions and respond openly about subjects about which they have unique perspectives.

Multiple endocrine neoplasia type 2a (MEN2a): a call for psycho-social research

This paper summarizes what is known about the diagnosis, treatment, and follow-care of people with the inherited disorder multiple endocrine neoplasia type 2a (MEN2a). Several databases were searched throughout the year 2000, including MEDLINE, CINAHL, CancerLit, PsychINFO, and Dissertation Abstracts International. MEN2a is a complex disease involving cancer care and control by surgery, health maintenance, and life-long observation of gene mutation carriers. Genetic testing is the standard of care, prophylactic surgery is recommended during directive counseling, and life-long surveillance is encouraged for people with MEN2a. A substantial body of scientific literature describes morbidity and mortality outcomes of disease treatment, and the monitoring of multiple organ systems. Research is scant concerning the psychological consequences and social impact of the MEN2a diagnosis, treatment, and follow-up. Nearly all that is known from a psycho-social perspective comes from data in The Netherlands. Little is known of the psychological responses to and social consequences of genetic predisposition testing, prophylactic and curative surgery, and life-long surveillance. Psycho-social research is essential to provide comprehensive care for patients and family members with this disorder and it is necessary to guide the development of risk management strategies for patients with this inherited cancer syndrome. Since MEN2a has been labeled a prototype for medical genetics, information on MEN2a patient experiences may be relevant to the care of individuals with other inherited cancer syndromes.

Early onset of medullary thyroid carcinoma in a kindred with multiple endocrine neoplasia type iia associated with cutaneous lichen amyloidosis

OBJECTIVE

To describe the molecular characterization of a kindred affected by the rare variant of multiple endocrine neoplasia type IIA (MEN IIA) associated with cutaneous lichen amyloidosis and to discuss the clinical implications in the management of this syndrome.

METHODS

A kindred with four affected family members was identified, and DNA analysis was performed by sequencing exon 11 of the RET proto-oncogene. Presymptomatic genetic screening was offered to all first-degree relatives.

RESULTS

Sequencing analysis of the RET proto-oncogene revealed a Cys634Trp (TGC->TGG) mutation in all clinically affected family members and in an asymptomatic 5-year-old child who, after thyroidectomy, was found to have multicentric medullary thyroid carcinoma and C-cell hyperplasia. A Gly691Ser (GGT->AGT) polymorphism was also detected in this family but did not segregate with the disease.

CONCLUSION

To our knowledge, this is the earliest detection of medullary thyroid carcinoma reported thus far in a kindred with MEN IIA associated with cutaneous lichen amyloidosis, and this finding suggests that prophylactic thyroidectomy, in kindreds with this variant, should be performed before the age of 5 years.

Germline RET 634 mutation positive MEN 2A-related C-cell hyperplasias have genetic features consistent with intraepithelial neoplasia

C-cell hyperplasias are normally multifocal in multiple endocrine neoplasia type 2A. We compared clonality, microsatellite pattern of tumor suppressor genes, and cellular kinetics of C-cell hyperplasia foci in each thyroid lobe. We selected 11 females from multiple endocrine neoplasia type 2A kindred treated with thyroidectomy due to hypercalcitoninemia. C-cell hyperplasia foci were microdissected for DNA extraction to analyze the methylation pattern of androgen receptor alleles and microsatellite regions (TP53, RB1, WT1, and NF1). Consecutive sections were selected for MIB-1, pRB1, p53, Mdm-2, and p21WAF1 immunostaining, DNA content analysis, and in situ end labeling. Appropriate tissue controls were run. Only two patients had medullary thyroid carcinoma foci. Nine informative C-cell hyperplasia patients showed germline point mutation in RET, eight of them with the same androgen receptor allele preferentially methylated in both lobes. C-cell hyperplasia foci showed heterogeneous DNA deletions revealed by loss of heterozygosity of TP53 (12 of 20), RB1 (6 of 14), and WT1 (4 of 20) and hypodiploid G0/G1 cells (14 of 20), low cellular turnover (MIB-1 index 4.5%, in situ end labeling index 0.03%), and significantly high nuclear area to DNA index ratio. MEN 2A (germline point mutation in RET codon 634) C-cell hyperplasias are monoclonal and genetically heterogeneous and show down-regulated apoptosis, findings consistent with an intraepithelial neoplasia. Concordant X-chromosome inactivation and interstitial gene deletions suggest clone expansions of precursors occurring at a point in embryonic development before divergence of each thyroid lobe and may represent a paradigm for other germline mutations.

Genetic markers in thyroid neoplasia

Cancer is a disease of genes. Detection of genetic abnormalities associated with cancers of various cell types can now be used for genetic counseling, diagnosis or treatment selection. In the case of thyroid cancer, genetic testing for mutations of the RET oncogene has had a profound effect on the management of medullary thyroid carcinomas. There is also considerable information on the genetic changes associated with development and progression of cancers of thyroid follicular cells, although these have not yet proven to be of practical value for clinical diagnosis or to guide prognosis and therapy.

Multiple endocrine neoplasia type iia: report of a family with a study of three generations in qatar

OBJECTIVE

To study the pattern of multiple endocrine neoplasia type IIA (MEN IIA) and describe the clinical features and results of genetic testing and treatment in 21 members of the first reported family with MEN IIA in Qatar.

METHODS

After identification of the proband, we screened all her family members (21 members) with genetic testing for the RET proto-oncogene mutation. Those subjects with the mutation were further assessed for pheochromocytoma by measurement of the 24-hour urinary vanillylmandelic acid, metanephrines, and catecholamines, and those with high levels underwent a metaiodobenzylguanidine scan and adrenalectomy. The serum calcium was measured in a effort to detect hyperparathyroidism. Those family members who had the mutation and were eligible for surgical treatment underwent total thyroidectomy and central compartment dissection. In those patients with high postoperative calcitonin levels, residual disease was sought with radiologic imaging, and follow-up was done with pentagastrin stimulation tests.

RESULTS

Of the 21 family members screened, 10 had the RET proto-oncogene mutation (codon 634, TGC->GGC) (5 females and 5 males; 6 adults and 4 children). All the adults had bilateral medullary thyroid carcinoma (MTC); four of them had lymph node metastatic lesions, and one had metastatic involvement of the liver. Two adults had pheochromocytomas. Two family members were reported to have parathyroid hyperplasia, although both were normocalcemic.

CONCLUSION

This family with MEN IIA showed classic mendelian autosomal dominant inheritance. All adult patients had MTC, two had pheochromocytomas, and two had parathyroid hyperplasia. Although one child had a high stimulated calcitonin level, the histopathologic findings were normal; another child with high stimulated calcitonin levels showed C-cell hyperplasia on histopathologic examination.

Sporadic type composite pheochromocytoma with neuroblastoma: clinicomorphologic, DNA content and ret gene analysis

Composite pheochromocytomas (CP) account for only 3% of all pheochromocytomas. We analyzed the clinical, immunohistochemical, ultrastructural, DNA content, and 634 ret mutation features in a 56-year-old Mexican woman with CP localized in the right adrenal gland and associated to a blood pressure of 140/90 mmHg. Clinical symptoms were absent after surgery. The tumor showed pheochromocytoma and neuroblastoma components. This dual phenotype was supported by light microscopy and corroborated by immunohistochemistry and ultrastructural findings. Flow cytometric analysis showed that both components were diploid. A genetic mutational analysis of the ret oncogene in exon 11 showed no 634 mutation. This case demonstrates the indolent behavior of neuroblastoma associated to a sporadic-type CP in an adult patient.

Clonal patterns in phaeochromocytomas and MEN-2A adrenal medullary hyperplasias: histological and kinetic correlates

The relationship among histological features, cell kinetics, and clonality has not been studied in adrenal medullary hyperplasias (AMHs) and phaeochromocytomas (PCCs). Thirty-four PCCs (23 sporadic and 11 MEN-2A (multiple endocrine neoplasia type 2A)-related tumours, the latter associated with AMH) from females were included in this study. Representative samples were histologically evaluated and microdissected to extract DNA and evaluate the methylation pattern of the androgen receptor alleles. At least two tissue samples (from the peripheral and internal zones in each tumour) were analysed with appropriate tissue controls run in every case. The same areas were selected for MIB-1 staining and in situ end labelling (ISEL). Malignant PCCs were defined by histologically confirmed distant metastases. All monoclonal AMH nodules from the same patient showed the same X-chromosome inactivated. Six sporadic PCCs revealed liver metastases (malignant PCC) and eight additional sporadic PCCs showed periadrenal infiltration (locally invasive PCC). All informative PCCs were monoclonal, except for five locally invasive PCCs and one benign PCC that revealed polyclonal patterns. Those cases also showed a fibroblastic stromal reaction with prominent blood vessels, focal smooth muscle differentiation, and significantly higher MIB-1 (126.8+/-29.9) and ISEL (50.9+/-12.8) indices. Concordant X-chromosome inactivation in nodules from a given patient suggests that MEN-2A AMH is a multifocal monoclonal condition. A subgroup of PCCs characterized by balanced methylation of androgen receptor alleles, high cellular turnover, and stromal proliferation also shows locally invasive features.

Multiple endocrine neoplasias

The multiple endocrine neoplasia syndromes form a distinct group of genetic tumor syndromes. They include multiple endocrine neoplasia types 1 and 2, von Hippel Lindau syndrome, neurofibromatosis, and Carney complex. Research over the past decade has identified a molecular basis for each of these syndromes. This knowledge has revolutionized not only the clinical management but also has illuminated the field of human cancer research by the identification of new and important genes critical for regulation of cell growth, differentiation, and death. This review focuses on the structure, physiologic function, and molecular abnormalities of the genes involved in these syndromes.

Initial results from a prospective cohort study of 5583 cases of thyroid carcinoma treated in the united states during 1996. U.S. and German Thyroid Cancer Study Group. An American College of Surgeons Commission on Cancer Patient Care Evaluation study

BACKGROUND

The American College of Surgeons Commission on Cancer (CoC) has conducted national Patient Care Evaluation (PCE) studies since 1976.

METHODS

Over 1500 hospitals with CoC-approved cancer programs were invited to participate in this prospective cohort study of U.S. thyroid carcinoma cases treated in 1996. Follow-up will be conducted through the National Cancer Data Base.

RESULTS

Of the 5584 cases of thyroid carcinoma, 81% were papillary, 10% follicular, 3.6% Hürthle cell, 0.5% familial medullary, 2.7% sporadic medullary, and 1.7% undifferentiated/anaplastic. Demographics and suspected risk factors were analyzed. Fine-needle aspiration of the thyroid gland (53%) or a neck lymph node (7%), thyroid nuclear scan (39%), and ultrasound (38%) constituted the most frequently utilized diagnostic modalities. The vast majority of patients with differentiated thyroid carcinoma presented with American Joint Committee on Cancer Stage I and II disease and relatively small tumors. For all histologies, near-total or total thyroidectomy constituted the dominant surgical treatment. No lymph nodes were examined in a substantial proportion of cases. Residual tumor after the surgical event could be documented in 11% of cases, hypocalcemia in 10% of cases, and recurrent laryngeal nerve injury in 1.3% of cases. Complications were most frequently associated with total thyroidectomy combined with lymph node dissection. Thirty-day mortality was 0.3%; when undifferentiated/anaplastic cancer cases were eliminated, it decreased to 0.2%. Adjuvant treatment, probably underreported in this study, consisted of hormonal suppression (50% overall) and radioiodine (50% overall).

CONCLUSIONS

In addition to offering information concerning risk factors and symptoms, the current PCE study compliments the survival information from previous NCDB reports and offers a surveillance snapshot of current management of thyroid carcinoma in the U.S. Identified opportunities for improvement of care include 1) more frequent use of fine-needle aspiration cytology in making a diagnosis; 2) more frequent use of laryngoscopy in evaluating patients preoperatively, especially those with voice change; and 3) improved lymph node resection and analysis to improve staging and, in some situations, outcomes.

RET proto-oncogene mutations in thyroid carcinomas: clinical relevance

Different forms of RET mutations are found in papillary and medullary thyroid carcinomas. Rearrangements with other genes (RET/PTC oncogene) play a causative role in a significant proportion of papillary thyroid carcinomas. In this case, several factors influence the frequency and the type of RET/PTC, such as exposure to radiation, age and histological variant of the papillary tumor. On the other hand, the presence of the mutation does not seem to influence the biological behavior of the tumor or its response to conventional treatment modalities. In the setting of medullary thyroid cancer, germline RET point-mutations are implicated in the pathogenesis of virtually all hereditary forms and somatic point-mutations in nearly half of the sporadic forms. The clinical impact of this finding is that family members at-risk of hereditary MTC may be screened by genetic analysis, to distinguish those carrying or not-carrying the mutation. The last can be reassured on their status and relieved from further follow-up. Those with the mutation may be treated at a pre-clinical stage of the disease or even before the disease is started. The present review is focused on the clinical implication of RET gene mutations in thyroid cancer patients.

Medullary carcinoma of the thyroid

Medullary thyroid cancer (MTC) is a distinct C-cell tumor of the thyroid. We review the oncogenesis and management of both sporadic tumors and those tumors arising as part of specific inherited syndromes. The RET proto-oncogene plays a role in the development of inherited forms of MTC and has become important in the clinical management of patients and their families. The recognition of the high rate of regional nodal involvement has led to lymphadenectomy being strongly considered for patients undergoing thyroidectomy for MTC.

Rapid MEN 2A gene carrier identification using primer-specific PCR amplification

DNA testing is of great importance in families with multiple endocrine neoplasia (MEN) type 2A to identify non-mutant carrying family members and asymptomatic mutation carriers, and also to confirm the diagnosis in patients who already show clinical or biochemical signs of disease. Several point mutations of the RET proto-oncogene on exons 10 and 11 are associated with the disease, which is characterized by medullary thyroid carcinoma, pheochromocytoma and hyperparathyroidism. The aim of the present study was to develop and evaluate a simple method, which indicates the mutational status of members of families where the site of the point mutation is known. The method is illustrated by the detection of mutation TGC-->TAC of codon 611, which is one of the well-known mutations associated with MEN 2A. The method involves the PCR technique with allele-specific primers and detection of the amplified sequences with biotinylated probes. There was a clear-cut difference between the readings from affected and unaffected subjects. The subjects had been evaluated independently and all subjects harboring the mutation also had clinical disease. The method provides a simple and reliable diagnostic tool for DNA screening of members of families with a known mutation of the RET-gene.

Presymptomatic detection and treatment of Japanese carriers of the multiple endocrine neoplasia type 2A gene

DNA extracted from the peripheral blood leukocytes of 36 members of five families with multiple endocrine neoplasia (MEN) type 2A was analyzed for mutations of exons 10, 11, 13, 14, and 16 of the RET proto-oncogene by nonisotopic polymerase chain reaction-single-strand conformation polymorphism analysis and automated DNA sequencing. Germline mutations were found in all 9 of the affected individuals and in 6 of the 27 individuals of unknown status. A 70-year-old man who had been completely asymptomatic before genetic diagnosis underwent left adrenalectomy and total thyroidectomy, and was found to have pheochromocytoma and multifocal micromedullary thyroid carcinoma (MTC). A 32-year-old man and a 15-year-old boy, with elevated calcitonin levels detected by the C-cell-stimulation test, but no evident thyroid tumor, underwent total thyroidectomy. Histopathological diagnosis revealed multiple micro MTCs. A 7-year-old girl without evidence of a thyroid tumor or an elevated calcitonin level is being followed up. The remaining two subjects with an evident thyroid tumor and elevated calcitonin levels refused surgery. These results suggest that genetic screening for MEN type 2 afflicted family members can facilitate the presymptomatic detection of gene carriers. Thus, we must carefully evaluate whether immediate prophylactic total thyroidectomy is indicated for gene carriers of MEN 2A without an evident thyroid tumor or elevated calcitonin levels.

Predictive DNA testing for multiple endocrine neoplasia 2: a therapeutic challenge of prophylactic thyroidectomy in very young children

BACKGROUND

Patients with multiple endocrine neoplasia (MEN) type 2 are at risk for early medullary thyroid carcinoma (MTC). Recently, the cloning of the ret oncogene has made it possible to identify patients at risk for MEN 2 syndrome with a high degree of reliability before presenting any symptoms.

METHODS

Children of families with MEN 2 were screened genetically if one of the parents was a known gene carrier of the RET proto-oncogene. If they were carriers, thyroidectomy was performed.

RESULTS

The authors report five children with MEN 2 who underwent prophylactic thyroidectomy irrespective of the results of calcitonin screening tests after genetic screening had shown that they were carrier of the RET proto-oncogene. Apart from a temporary hypocalcemia in one, the operations were uneventful. Pathology results showed MTC in three children of one family with MEN 2A at age 2, 3, and 6 years. In two families with MEN 2B the thyroidectomy specimen showed bilateral MTC in a 1-year-old and a 3-year-old child.

CONCLUSIONS

These findings show that MTC occurs at very young age in children with MEN 2. The authors advocate performing prophylactic thyroidectomy in the first year of life in children with MEN 2B and at age 2 years in children with MEN 2A to obtain an optimal cure rate.

Abordagem clínica e laboratorial do bócio uninodular sólido: vantagens da determinação da calcitonina sérica por métodos distintos no rastreamento do carcinoma medular de tireóide, forma esporádica

A apresentação clínica mais freqüente da forma esporádica do carcinoma medular da tireóide (CMT) é o bócio uninodular sólido (BUS), apresentação esta semelhante aos demais tumores que afetam a glândula. O estabelecimento da freqüência de CMT em BUS apresenta implicações importantes não só diagnosticas, como também terapêuticas, visto a abordagem cirúrgica do CMT diferir de outros tumores tireoideanos. Para investigar a prevalência de CMT em BUS, dosamos calcitonina (CT) sérica, marcador bioquímico do CMT, por métodos distntos (RIA e IRMA) em 60 casos (55 mulheres; com idades entre 22 e 75 anos). A análise citológica obtida através de punção biópsia (PAAF) revelou 100% de especificidade e 67% de sensibilidade na detecção de carcinoma de tireóide. Considerando-se o grau de suspeita clínica para neoplasia tireoideana e os achados anatomopatológicos, houve 60% de correlação positiva. CMT foi diagnosticado através da elevação da CT sérica em um dos 59 casos (1,69%) e confirmado posteriormente pela PAAF e anatomopatológico. A incidência de CMT entre os casos de neoplasias tireoideanas nesta amostra foi de 12,5% (1/8). Concluímos que a dosagem rotineira da CT sérica em casos com BUS não só complementa o estudo desta doença, como auxilia fortemente no diagnóstico do CMT. Tanto o IRMA como o RIA mostraram-se métodos úteis no rastreamento do CMT. Entretanto, o RIA pode provavelmente detectar ainda mais precocemente a elevação de formas não monoméricas da molécula de CT, as quais nos casos de CMT são usualmente mais abundantes que as formas monoméricas.

Ret-proto-oncogene analysis in medullary thyroid carcinoma

INTRODUCTION

Medullary carcinoma of the thyroid (MTC) is a rare tumour which occurs in both sporadic and hereditary forms. Mutations of the RET proto-oncogene have been identified in hereditary forms. The aim of our study was to confirm or exclude familial disease by examining for germline mutations in the RET proto-oncogene in patients with medullary thyroid carcinoma.

METHODS

Nine patients with medullary thyroid carcinoma and 4 of their children were studied. Peripheral blood was used to examine for mutations in the RET proto-oncogene. When this was not available, archival thyroid tissue was used.

RESULTS

Seven patients had clinically sporadic tumours confirmed by mutational analysis of RET. Four children were at risk of being carriers of a mutated gene, as their fathers had histologically proven MTC and had tested positive for the mutation at codon 618 on exon 10 of the RET proto-oncogene. Three of these children carried the 618 mutation. To date, 2 have had a prophylactic thyroidectomy, the pathology of which revealed C-cell hyperplasia. One child had familial disease excluded by mutational analysis. One patient had a clinical diagnosis of MEN2B confirmed by detection of the 918 mutation on exon 16 of the RET proto-oncogene.

CONCLUSIONS

RET proto-oncogene analysis is a reliable method of differentiating familial from sporadic MTC. Mutational information determines which family members of affected kindreds are at risk of developing the disease and can be used to affect clinical management.

Current diagnosis and management of medullary thyroid carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) originates in the thyroid C cells, accounting for 5% to 10% of all thyroid malignancies. Approximately 75% of cases are sporadic. Significant advances have been made in the molecular biology of MTC, but some aspects of diagnosis and management still remain controversial.

DESIGN

We reviewed relevant articles published in major English-language medical journals. We used the MEDLINE database, selected bibliographies, and articles available in our personal files.

RESULTS

Mutations of the RET proto-oncogene have been identified in the germline DNA of patients with familial MTC syndromes. Genetic testing can identify patients affected by multiple endocrine neoplasia types IIA and IIB and familial MTC, allowing early diagnosis and possible cure. Surgical treatment is total thyroidectomy. Plasma calcitonin measurements are excellent markers for postoperative follow-up. Adjunctive therapy includes radiotherapy and chemotherapy. The overall prognosis is worse than papillary thyroid carcinoma.

CONCLUSIONS

Recent advances in genetic testing allow early diagnosis and treatment of familial MTC syndromes. Despite some advances in treatment, optimal management remains controversial.

Advances and controversies in the diagnosis and management of medullary thyroid carcinoma

Recent advances in the diagnosis and treatment of medullary thyroid carcinoma (MTC) have been significant, but some issues remain controversial. MTC may occur either as a hereditary or a nonhereditary entity. Hereditary MTC can occur either alone--familial MTC (FMTC)--or as the thyroid manifestation of multiple endocrine neoplasia type 2 (MEN 2) syndromes (MEN 2A and MEN 2B). These hereditary disorders are due to germline mutations in the RET proto-oncogene. Early diagnosis and treatment considerably improve the prognosis in patients with MTC. Genetic testing can identify almost all affected individuals with hereditary disease and permits early thyroidectomy in gene carriers. Plasma CT is an excellent marker for postoperative follow-up. Imaging studies help delineate recurrent or metastatic lesions. Treatment of recurrent or metastatic disease is primarily surgical, including either palliative or microdissective surgery. Radiation therapy is reserved for skeletal metastasis or nonresectable metastatic MTC. Efficacy of current chemotherapy programs is not well established. Overall, the 10-year survival rates are approximately 65%.

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.

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.

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.