Medullary thyroid carcinoma as part of a multiple endocrine neoplasia type 2B syndrome: influence of the stage on the clinical course

This is Your Thyroid on Drugs: Targetable Mutations and Fusions in Thyroid Carcinoma

This review aims to provide an overview of the molecular pathogenesis thyroid carcinomas, emphasizing genetic alterations that are therapeutically actionable. The main pathways in thyroid carcinogenesis are the MAPK and PI3K pathways. Point mutations and gene rearrangements affecting the pathway effectors and receptor tyrosine kinases are well-known drivers of thyroid cancer. Research over the past few decades has successfully introduced highly effective treatments for unresectable thyroid cancer, evolving from multi-kinase inhibitors to structurally selective agents, with constantly improving toxicity profiles and coverage of resistance mechanisms. The pros and cons of major laboratory techniques for therapeutic target identification are discussed.

Timely diagnosis of multiple endocrine neoplasia 2B by identification of intestinal ganglioneuromatosis: a case series

BACKGROUND

Medullary thyroid carcinoma (MTC) in childhood is rare and has an unfavorable prognosis. To improve outcome, early diagnosis is essential. In patients with multiple endocrine neoplasia type 2B (MEN2B), MTC can occur already before the age of 1 year. Recognition of non-endocrine features of MEN2B may lead to timely diagnosis.

PURPOSE

To describe how early recognition of non-endocrine features can lead to a timely diagnosis of MEN2B as well as the effect of recognition of premonitory symptoms on prognosis.

METHODS

A retrospective case series from the University Medical Center Utrecht/Wilhelmina Children's Hospital, a Dutch national expertise center for MEN patients. All eight MEN2B patients in follow-up between 1976 and 2020 were included and medical records reviewed.

RESULTS

Intestinal ganglioneuromatosis (IGN) as the cause of gastrointestinal (GI) symptoms was detected in seven patients. In three of them within months after birth. This led to early diagnosis of MEN2B, which allowed subsequent curative thyroid surgery. On the contrary, a MEN2B diagnosis later in childhood-in three patients (also) triggered by oral neuromas/neurofibromas-led to recurrent, persistent, and/or progressive MTC in five patients.

CONCLUSIONS

Neonatal GI manifestations offer the most important window of opportunity for early detection of MEN2B. By accurate evaluation of rectal biopsies in patients with early onset severe constipation, IGN can be timely detected, while ruling out Hirschsprung's disease. MEN2B gene analysis should follow detection of IGN and-when confirmed-should prompt possibly still curative thyroid surgery.

Screening for Hereditary Pheochromocytoma in a Patient with Neurofibromatosis Type 1: A Case Report

Pheochromocytoma (PHEO) is a rare tumour that arises from adreno-medullary chromaffin cells and secretes catecholamines. These hormones are also secreted by paragangliomas, which derive from extra-adrenal cells of the sympathetic paravertebral ganglia. At least one-third of PHEOs are familial. Neurofibromatosis type 1 (NF1), or von Recklinghausen's disease, is diagnosed upon clinical criteria, and the study of PHEO is advised if hypertension is present. The incidence of PHEO in NF1 is 0.1-5.7% and explains hypertension in 20-50% of these patients. Recent advances in the treatment of this condition and preoperative preparation allow us to reduce its high cardiovascular morbimortality. Here we present the case of a 31-year-old female with known NF1 who presented with 5 months' history of non-specific symptoms and an episode of intraoperative hypertensive crisis. The workup detected a left sided PHEO, which was treated surgically. Our case illustrates the high prevalence of hereditary PHEO and how its presentation can go unnoticed. It reinforces the significance of screening for PHEO in patients with NF1.

Screening for Hereditary Pheochromocytoma in a Patient with Neurofibromatosis Type 1: A Case Report

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Severe constipation as the first clinical manifestation in multiple endocrine neoplasia type 2B: a case report and literature review

BACKGROUND

The occurrence of multiple endocrine neoplasia type 2B (MEN2B) in Asians is very rare. In particular, patients with intractable constipation as the main clinical manifestation are even rarer. Atypical clinical manifestations are likely to lead to a diagnostic delay. In this report, we described a case of a delayed diagnosis of MEN2B, and the first clinical manifestation was intractable constipation.

CASE PRESENTATION

A female teenager had suffered from intractable constipation since infancy. Because the colonoscopy and biopsy results from local hospitals did not confirm the presence of congenital megacolon, the girl had been followed up at a local clinic for a long time. The diagnosis was not confirmed until thyroid masses were found in the Pediatric Department of Shanghai Ruijin Hospital when she was 12 years old. According to our detailed evaluation, she suffered from Hirschsprung disease (HD), growth retardation, medullary thyroid carcinoma (MTC) and mucosal neuroma due to a mutation in the RET gene. Thus, the diagnosis of MEN2B was confirmed. Afterward, the girl underwent several surgeries and was still being followed up before the article was published.

CONCLUSION

MEN2B has atypical clinical symptoms in the early stage. Refractory constipation may be the only clinical manifestation that lasts for several years. Therefore, we recommend that early screening and gene sequencing should be performed for patients with severe constipation due to HD to determine the cause of the disease and to improve the survival outcome.

Natural history, treatment, and long-term follow up of patients with multiple endocrine neoplasia type 2B: an international, multicentre, retrospective study

BACKGROUND

Multiple endocrine neoplasia type 2B is a rare syndrome caused mainly by Met918Thr germline RET mutation, and characterised by medullary thyroid carcinoma, phaeochromocytoma, and extra-endocrine features. Data are scarce on the natural history of multiple endocrine neoplasia type 2B. We aimed to advance understanding of the phenotype and natural history of multiple endocrine neoplasia type 2B, to increase awareness and improve detection.

METHODS

This study was a retrospective, multicentre, international study in patients carrying the Met918Thr RET variant with no age restrictions. The study was done with registry data from 48 centres globally. Data from patients followed-up from 1970 to 2016 were retrieved from May 1, 2016, to May 31, 2018. Our primary objectives were to determine overall survival, and medullary thyroid carcinoma-specific survival based on whether the patient had undergone early thyroidectomy before the age of 1 year. We also assessed remission of medullary thyroid carcinoma, incidence and treatment of phaeochromocytoma, and the penetrance of extra-endocrine features.

FINDINGS

345 patients were included, of whom 338 (98%) had a thyroidectomy. 71 patients (21%) of the total cohort died at a median age of 25 years (range <1-59). Thyroidectomy was done before the age of 1 year in 20 patients, which led to long-term remission (ie, undetectable calcitonin level) in 15 (83%) of 18 individuals (2 patients died of causes unrelated to medullary thyroid carcinoma). Medullary thyroid carcinoma-specific survival curves did not show any significant difference between patients who had thyroidectomy before or after 1 year (comparison of survival curves by log-rank test: p=0·2; hazard ratio 0·35; 95% CI 0.07-1.74). However, there was a significant difference in remission status between patients who underwent thyroidectomy before and after the age of 1 year (p<0·0001). There was a significant difference in remission status between patients who underwent thyroidectomy before and after the age of 1 year (p<0·0001). In the other 318 patients who underwent thyroidectomy after 1 year of age, biochemical and structural remission was obtained in 47 (15%) of 318 individuals. Bilateral phaeochromocytoma was diagnosed in 156 (50%) of 313 patients by 28 years of age. Adrenal-sparing surgery was done in 31 patients: three (10%) of 31 patients had long-term recurrence, while normal adrenal function was obtained in 16 (62%) patients. All patients with available data (n=287) had at least one extra-endocrine feature, including 106 (56%) of 190 patients showing marfanoid body habitus, mucosal neuromas, and gastrointestinal signs.

INTERPRETATION

Thyroidectomy done at no later than 1 year of age is associated with a high probability of cure. The reality is that the majority of children with the syndrome will be diagnosed after this recommended age. Adrenal-sparing surgery is feasible in multiple endocrine neoplasia type 2B and affords a good chance for normal adrenal function. To improve the prognosis of such patients, it is imperative that every health-care provider be aware of the extra-endocrine signs and the natural history of this rare syndrome. The implications of this research include increasing awareness of the extra-endocrine symptoms and also recommendations for thyroidectomy before the age of 1 year.

FUNDING

None.

Medullary Thyroid Cancer: Clinical Characteristics and New Insights into Therapeutic Strategies Targeting Tyrosine Kinases

Medullary thyroid carcinoma (MTC) is a hyperplasia of thyroid C-cells, accounting for 5-10% of all thyroid cancers. MTCs may appear as sporadic or hereditary forms, and several molecules and signaling pathways have been found to function defectively in MTC cells. Tyrosine kinases are the most well-studied molecules that have abnormal function in these tumor cells. Due to their limited response, chemotherapeutic agents and radiation therapy are not effective in treating patients with advanced metastatic MTC. In the past decade, significant attention has been given to the utilization of multikinase inhibitors as targeted therapeutic agents for treating MTC patients, with the most promising results arising from the study of tyrosine kinase inhibitors, which generally bind to the ATP binding sites of these kinases. Two drugs-vandetanib and cabozantinib-are approved for the treatment of aggressive advanced MTC; however, the potential for toxicities and adverse effects of these agents on patient quality of life need to be considered against any therapeutic gain. According to recent data, it appears that inhibition of only one receptor or molecule in a pathway is not as effective as simultaneous inhibition of different pathways, indicating the need to use combination therapy. The main purpose of this review is to describe the clinical characteristics, molecular mechanisms, and current molecular and targeted therapeutic strategies active in clinical trials for advanced MTC treatment.

Molecular markers of paragangliomas/pheochromocytomas

Paragangliomas/pheochromocytomas comprise rare tumors that arise from the extra-adrenal paraganglia, with an incidence of about 2 to 8 per million people each year. Approximately 40% of cases are due to genetic mutations in at least one out of more than 30 causative genes. About 2530% of pheochromocytomas/paragangliomas develop under the conditions of a hereditary tumor syndrome a third of which are caused by mutations in the VHL gene. Together, the gene mutations in this disorder have implicated multiple processes including signaling pathways, translation initiation, hypoxia regulation, protein synthesis, differentiation, survival, proliferation, and cell growth. The present review contemplates the mutations associated with the development of pheochromocytomas/paragangliomas and their potential to serve as specific markers of these tumors and their progression. These data will improve our understanding of the pathogenesis of these tumors and likely reveal certain features that may be useful for early diagnostics, malignancy prognostics, and the determination of new targets for disease therapeutics.

A comprehensive review on MEN2B

MEN2B is a very rare autosomal dominant hereditary tumor syndrome associated with medullary thyroid carcinoma (MTC) in 100% cases, pheochromocytoma in 50% cases and multiple extra-endocrine features, many of which can be quite disabling. Only few data are available in the literature. The aim of this review is to try to give further insights into the natural history of the disease and to point out the missing evidence that would help clinicians optimize the management of such patients. MEN2B is mainly characterized by the early occurrence of MTC, which led the American Thyroid Association to recommend preventive thyroidectomy before the age of 1 year. However, as the majority of mutations are de novo, improved knowledge of the nonendocrine signs would help to lower the age of diagnosis and improve long-term outcomes. Future large-scale studies will be aimed at characterizing more in detail the main characteristics and outcomes of MEN2B.

A Clinical Roadmap to Investigate the Genetic Basis of Pediatric Pheochromocytoma: Which Genes Should Physicians Think About?

Pheochromocytoma is very rare at a pediatric age, and when it is present, the probability of a causative genetic mutation is high. Due to high costs of genetic surveys and an increasing number of genes associated with pheochromocytoma, a sequential genetic analysis driven by clinical and biochemical phenotypes is advised. The published literature regarding the genetic landscape of pediatric pheochromocytoma is scarce, which may hinder the establishment of genotype-phenotype correlations and the selection of appropriate genetic testing at this population. In the present review, we focus on the clinical phenotypes of pediatric patients with pheochromocytoma in an attempt to contribute to an optimized genetic testing in this clinical context. We describe epidemiological data on the prevalence of pheochromocytoma susceptibility genes, including new genes that are expanding the genetic etiology of this neuroendocrine tumor in pediatric patients. The clinical phenotypes associated with a higher pretest probability for hereditary pheochromocytoma are presented, focusing on differences between pediatric and adult patients. We also describe new syndromes, as well as rates of malignancy and multifocal disease associated with these syndromes and pheochromocytoma susceptibility genes published more recently. Finally, we discuss new tools for genetic screening of patients with pheochromocytoma, with an emphasis on its applicability in a pediatric population.

Long-Term Survivorship in Multiple Endocrine Neoplasia Type 2B Diagnosed Before and in the New Millennium

CONTEXT

Recent long-term outcomes and survival data are lacking for patients with multiple endocrine neoplasia type 2B (MEN2B).

OBJECTIVES

To analyze long-term MEN2B outcomes and define prognostic factors.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective comparative study of 75 patients with MEN2B from two German tertiary referral centers. Patients diagnosed and treated before and after 2000 were compared for demographic, biochemical, surgical, and outcome parameters.

INTERVENTION

Surgery.

MAIN OUTCOME MEASURE

Long-term survival.

RESULTS

We identified seven familial and 68 de novo cases of MEN2B; 61 exhibited the RET M918T genotype (2 others exhibited A883F and E768D/L790T mutations). Surgery was performed at a mean age of 16.4 ± 11.2 years. The tumor stages at diagnosis for 71 patients were stage I, 15%; stage II, 6%; stage III, 35%; and stage IV, 44%. The mean follow-up was 9.6 ± 9.0 years. The outcomes were 15 (20%) cured, 9 (12%) with minimal residual disease, 19 (25%) with metastatic disease, and 10 (13%) unknown. Medullary thyroid cancer (MTC) caused 22 deaths (29%) 7.3 ± 6.2 years after diagnosis (mean age, 22.9 ± 10.7 years). The overall survival rates at 5, 10, and 20 years were 85%, 74%, and 58%, respectively. After 2000 (vs before 2000), significantly more patients had stage I and II (32% vs 11%) and more were cured (43% vs 20%), with a higher survival trend (P = 0.058). The only prognostic factor was tumor stage at diagnosis.

CONCLUSIONS

Patients with MEN2B developed MTC at an early age with wide ranging aggressiveness, but the outcome was generally better after 2000 than before 2000.

Identification of intestinal ganglioneuromatosis leads to early diagnosis of MEN2B: role of rectal biopsy

BACKGROUND/PURPOSE

Gastrointestinal symptoms are very common in patients with multiple endocrine neoplasia type 2B (MEN2B) syndrome. Herein, we present a case of intestinal ganglioneuromatosis (IGN) in MEN2B syndrome and a systematic literature review with a special focus on gastrointestinal symptoms prior to the diagnosis of MEN2B.

METHODS

Literature search was performed (years 1966-2015) using the "Pubmed" and "Scopus" databases. Search terms used were gastrointestinal, intestinal and MEN2B.

RESULTS

Literature search revealed 188 publications on MEN2B patients with gastrointestinal symptoms, providing a total of 55 patients including our own case. The far most common gastrointestinal symptom was constipation (72.7%). The onset of gastrointestinal symptoms occurred in 29 out of 55 cases (52.3%) below the age of 1year. However, MEN2B diagnosis was established at a median age of 13.0years (range 0-46years). The histological finding of IGN led to the diagnosis of MEN2B In 15 of 55 patients (27.3%) at a median age of 3years (range 0-31years).

CONCLUSION

Paying close attention to gastrointestinal problems in early childhood and taking a rectal biopsy that precisely screens for IGN offers the chance of diagnosing MEN2B syndrome early in infancy.

Risk Profile of the RET A883F Germline Mutation: An International Collaborative Study

CONTEXT

The A883F germline mutation of the rearranged during transfection (RET) proto-oncogene causes multiple endocrine neoplasia 2B. In the revised American Thyroid Association (ATA) guidelines for the management of medullary thyroid carcinoma (MTC), the A883F mutation has been reclassified from the highest to the high-risk level, although no well-defined risk profile for this mutation exists.

OBJECTIVE

To create a risk profile for the A883F mutation for appropriate classification among the ATA risk levels.

DESIGN

Retrospective analysis.

SETTING

International collaboration.

PATIENTS

Included were 13 A883F carriers.

INTERVENTION

The intervention was thyroidectomy.

MAIN OUTCOME MEASURES

Earliest age of MTC, regional lymph node metastases, distant metastases, age-related penetrance of MTC and pheochromocytoma (PHEO), overall and disease-specific survival, and biochemical cure rate.

RESULTS

One and three carriers were diagnosed at age 7 to 9 years (median, 7.5 years) with a normal thyroid and C-cell hyperplasia, respectively. Nine carriers were diagnosed with MTC at age 10 to 39 years (median, 19 years). The earliest age of MTC, regional lymph node metastasis, and distant metastasis was 10, 20, and 20 years, respectively. Fifty percent penetrance of MTC and PHEO was achieved by age 19 and 34 years, respectively. Five- and 10-year survival rates (both overall and disease specific) were 88% and 88%, respectively. Biochemical cure for MTC at latest follow-up was achieved in 63% (five of eight carriers) with pertinent data.

CONCLUSIONS

MTC of A883F carriers seems to have a more indolent natural course compared with that of M918T carriers. Our results support the classification of the A883F mutation in the ATA high-risk level.

Medullary Thyroid Carcinoma: Recent Advances Including MicroRNA Expression

Medullary thyroid carcinoma (MTC) is an uncommon neuroendocrine tumor arising from the C cells in the thyroid and accounts for about 5 % of all thyroid cancers. MTC exhibits more aggressive behavior than follicular tumors, with the majority of cases presenting with lymph node metastasis. It is particularly common among patients carrying germline RET mutations with almost 100 % penetrance. Because activating RET mutations occur in over 90 % of hereditary and 40 % of sporadic MTC, clinical trials of several RET-targeting multikinase inhibitors (MKIs) have resulted in FDA approval of vandetanib and cabozantinib for the treatment of MTC. Nevertheless, in light of significant individual differences in tumor behavior and treatment responses, there has been a persistent need for research efforts to decipher the molecular events within RET-driven or non-RET-driven tumors. Recently, the gene regulatory roles of microRNAs (miRNAs) in MTC have been studied extensively. Multiple miRNA deregulations have been discovered in MTC with potential prognostic and therapeutic implications. This review provides an overview of the basic pathology of MTC and an update on recent investigational progress.

Initial surgical management of medullary thyroid cancer

Medullary thyroid cancer (MTC) accounts for 5–10% of thyroid cancer. The majority, 75–80%, of MTC are sporadic with the remainder being hereditary secondary to a mutation in the RET proto-oncogene. Hereditary MTC may be isolated as in familial medullary thyroid cancer or associated with multiple endocrine neoplasia syndrome types 2A and 2B. The primary treatment modality for sporadic MTC is total thyroidectomy and central compartment neck dissection; consideration of lateral neck dissection should be based on preoperative imaging findings. The timing of prophylactic thyroidectomy is dependent on the specific RET codon mutation.

Multiple endocrine neoplasia syndromes 1 and 2: manifestations and management in childhood and adolescence

The identification of the genetic causes of the multiple endocrine neoplasia (MEN) syndromes 1 and 2, and associated genotype-phenotype relationships, has revolutionised the clinical care of affected patients. A genetic diagnosis can be made during infancy and careful clinical surveillance, coupled with early intervention, has the potential to improve both morbidity and mortality. These developments have seen the management of patients with MEN move into the arena of paediatric medicine. In this review article, we consider the genetic causes of MEN together with the clinical manifestations and management of these syndromes.

Molecular pathology of hereditary and sporadic medullary thyroid carcinomas

OBJECTIVES

Medullary thyroid carcinoma (MTC) is a relatively uncommon type of thyroid malignancy, with unique histologic features and molecular pathology. It is important to recognize, because its management, which is in part driven by the genetic basis of this disease, is different from follicular-derived thyroid tumors. The aim of this article is to briefly review the histopathologic features of MTC and then explore its molecular pathology, including the role of molecular diagnostic testing and the use of targeted therapy for advanced disease.

METHODS

A review of published literature was performed.

RESULTS

A subset of MTC cases is hereditary and due to germline mutations in the RET tyrosine kinase receptor gene. Somatic mutations in either RET or RAS are also present in most sporadic tumors.

CONCLUSIONS

Molecular genetic testing is routinely performed to identify hereditary cases. In addition, understanding the molecular basis of both hereditary and sporadic MTC has led to the development of targeted therapy with tyrosine kinase inhibitors. Although additional data are needed, tumor mutation status may affect response to targeted therapy. Therefore, it is possible that genetic testing of tumor tissue to predict treatment response, as is currently done for other cancer types, may come into practice in the future.

Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma

INTRODUCTION

The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association.

METHODS

The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document.

RESULTS

The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC.

CONCLUSIONS

The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice.

Surgical curability of medullary thyroid cancer in multiple endocrine neoplasia 2B: a changing perspective

OBJECTIVE

This investigation aimed at exploring the suitability of nonendocrine manifestations preceding medullary thyroid cancer (MTC) for early diagnosis of multiple endocrine neoplasia type 2B (MEN 2B).

BACKGROUND

MEN 2B patients, running a high risk of metastatic MTC, must be diagnosed early for biochemical cure.

METHODS

Forty-four MEN 2B patients carrying inherited (3 patients) and de novo (41 patients) M918T RET mutations were examined for signs and symptoms prompting MEN 2B.

RESULTS

All 3 patients with inherited mutations were diagnosed before the age of 1 year and cured of their C-cell disease. Among 41 patients with de novo mutations, MEN 2B was diagnosed in 12 patients after recognition of nonendocrine manifestations [intestinal ganglioneuromatosis (6 patients), oral symptoms (5 patients), ocular ("tearless crying") (4 patients), and skeletal stigmata (1 patient) alone or concomitantly]. In the remaining 29 patients with de novo mutations, the diagnosis of MEN 2B was triggered by symptomatic MTC (28 patients) or pheochromocytoma (1 patient). The former patients, being significantly (P < 0.001) younger (means of 5.3 vs 17.6 years) and having lower calcitonin levels (means of 115 vs 25,519 pg/mL), smaller tumors (67% vs 0% were ≤10 mm) and less often extrathyroidal extension (0% vs 81%), lymph node (42% vs 100%), and distant metastases (8% vs 79%), were biochemically cured more often (58% vs 0%).

CONCLUSIONS

MTC is curable in patients with de novo mutations when nonendocrine MEN 2B components are quickly appreciated and surgical intervention is performed before patients turn 4 years old.

Medullary thyroid carcinoma: surgical treatment advances

Since medullary thyroid cancer (MTC) was first recognized as a distinct tumor in 1959, it became clear that MTC is more difficult to cure than papillary thyroid cancer and has higher rates of recurrence and mortality. MTC represents 5-8% of thyroid cancers. It derives from parafollicular cells of the ultimobranchial body derived from the neural crest. MTC secretes calcitonin and other hormonal peptides and is considered part of the amine precursor uptake and decarboxilation system. MTC may occur either as a hereditary or nonhereditary entity. Hereditary MTC can occur either alone as the familial MTC or as the thyroid manifestation of multiple endocrine neoplasia (MEN) type 2 syndromes (MEN 2A MEN 2B). Activating point mutations of the RET proto-oncogene have demonstrated to be causative of the familial form of medullary thyroid cancer, both isolated familial MTC and associated with MEN 2A and 2B. In the last 10 years, major improvements and new technologies have been proposed and applied in thyroid surgery; among these are molecular diagnosis with genetic screening and mini-invasive video-assisted thyroidectomy. The history of thyroid surgery starts with Billroth, Kocher and Halsted, who developed the technique for thyroidectomy between 1873 and 1910. Prophylactic surgery for patients carrying a positive RET proto-oncogene has proven to be highly effective in curing those likely to experience the development of MTC. Video-assisted procedures with central compartment dissection have proved feasible for patients carrying a positive RET proto-oncogene. This paper reviews relevant medical literature published in the English language on surgery of MTC in well-controlled trials. We discuss the particular ethical and legal issues that thyroid prophylactic surgery raises. Searches were last updated in February 2007.

[Medullary thyroid carcinoma in children]

Medullary thyroid carcinoma (MTC) is rare in children. MTC is almost always inherited and occurs as part of a multiple endocrine neoplasia type 2A and B, due to germline mutation in the RET proto-oncogene. MTC in the pediatric population is most often diagnosed in the course of a familial genetic investigation. But when the child is the proband, a de novo mutation is most often founded. The main aim is to treat MTC before extrathyroidal extension occurs because when distant metastases are present, it is rarely curable. Treatment is based on total thyroidectomy with cervical lymph node dissection.

The genetics of neuroendocrine tumors

Neuroendocrine tumors (NETs) present a wide spectrum of malignant diseases from rather benign to very malignant variants. The majority of these tumors are sporadic, but there are several familial (inherited) syndromes to consider, such as multiple endocrine neoplasia type 1 and type 2 (MEN-1 and MEN-2), von Hippel-Lindau syndrome (VHL), tuberosclerosis, and neurofibromatosis syndromes. The MEN-1 gene is mutated not only in MEN-1 families, but a recent study shows that more than 40% of sporadic pancreatic NETs (PNETs) harbor MEN-1 gene mutations. The same study reported that ATRX/DAXX genes are mutated in a significant number of tumors, as are genes encoding components of the mammalian target of rapamycin (mTOR) signal transduction pathway. These findings have implications for the new therapies that have been approved for the treatment of PNETs, such as the tyrosine kinase inhibitor sunitinib, as well the mTOR inhibitor everolimus. Small intestinal NETs show a less varied mutational pattern in that the majority of genetic alterations are found on chromosome 18. There seem to be no differences between the sporadic and the familiar type of small intestinal NETs (carcinoids). A wide range of genetic alterations have been described for the different subtypes of NETs, but the mechanisms underlying tumor development are essentially unknown except for MEN-2, in which an activating mutation of the RET proto-oncogene drives tumor progression and affords a direct genotype/phenotype correlation. Genome-wide screening of different types of NETs can now be performed for a reasonable price and is likely to generate new insights into the tumor biology and carcinogenesis in various subtypes of NETs.

Molecular mechanisms of RET receptor-mediated oncogenesis in multiple endocrine neoplasia 2

Multiple endocrine neoplasia type 2 is an inherited cancer syndrome characterized by tumors of thyroid and adrenal tissues. Germline mutations of the REarranged during Transfection (RET) proto-oncogene, leading to its unregulated activation, are the underlying cause of this disease. Multiple endocrine neoplasia type 2 has been a model in clinical cancer genetics, demonstrating how knowledge of the genetic basis can shape the diagnosis and treatment of the disease. Here, we discuss the nature and effects of the most common recurrent mutations of RET found in multiple endocrine neoplasia type 2. Current understanding of the molecular mechanisms of RET mutations and how they alter the structure and function of the RET protein leading to its aberrant activation, and the effects on RET localization and signaling are described.

Genetics and clinical characteristics of hereditary pheochromocytomas and paragangliomas

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are rare neuroendocrine tumors of the adrenal glands and the sympathetic and parasympathetic paraganglia. They can occur sporadically or as a part of different hereditary tumor syndromes. About 30% of PCCs and PGLs are currently believed to be caused by germline mutations and several novel susceptibility genes have recently been discovered. The clinical presentation, including localization, malignant potential, and age of onset, varies depending on the genetic background of the tumors. By reviewing more than 1700 reported cases of hereditary PCC and PGL, a thorough summary of the genetics and clinical features of these tumors is given, both as part of the classical syndromes such as multiple endocrine neoplasia type 2 (MEN2), von Hippel-Lindau disease, neurofibromatosis type 1, and succinate dehydrogenase-related PCC-PGL and within syndromes associated with a smaller fraction of PCCs/PGLs, such as Carney triad, Carney-Stratakis syndrome, and MEN1. The review also covers the most recently discovered susceptibility genes including KIF1Bβ, EGLN1/PHD2, SDHAF2, TMEM127, SDHA, and MAX, as well as a comparison with the sporadic form. Further, the latest advances in elucidating the cellular pathways involved in PCC and PGL development are discussed in detail. Finally, an algorithm for genetic testing in patients with PCC and PGL is proposed.

Management of medullary thyroid carcinoma and MEN2 syndromes in childhood

Medullary thyroid carcinoma (MTC) and the multiple endocrine neoplasia (MEN) type 2 syndromes are rare but important endocrine diseases that are increasingly managed by pediatric providers. MTC is generally associated with a favorable prognosis when diagnosed during childhood, where it frequently occurs secondary to activating mutations in the RET proto-oncogene and arises from pre-existing C-cell hyperplasia. MEN2A accounts for 90-95% of childhood MTC cases and is most commonly due to mutations in codon 634 of RET. MEN2B is associated with the most aggressive clinical presentation of MTC and is almost always due to the Met918Thr mutation of RET. Surgery is the primary treatment and only chance of cure, although the advent of targeted therapies seems to be improving progression-free survival in advanced cases. Since the discovery of the role of RET in MEN2A, considerable advances in the management of this syndrome have occurred, and most of the children with MEN2A who have undergone early thyroidectomy will now lead full, productive lives. Strong genotype-phenotype correlations have facilitated the development of guidelines for interventions. Contemporary approaches for deciding the appropriate age at which surgery should take place incorporate data from ultrasonography and calcitonin measurements in addition to the results of genotyping. To optimize care and to facilitate ongoing research, children with MTC and the MEN2 syndromes are optimally treated at tertiary centers with multidisciplinary expertise.

Prognostic factors of disease-free survival after thyroidectomy in 170 young patients with a RET germline mutation: a multicenter study of the Groupe Francais d'Etude des Tumeurs Endocrines

BACKGROUND

In hereditary medullary thyroid carcinoma (HMTC), prophylactic surgery is the only curative option, which should be properly defined both in time and extent.

OBJECTIVES

To identify and characterize prognostic factors associated with disease-free survival (DFS) in children from HMTC families.

DESIGN

We conducted a retrospective analysis of a multi-center cohort of 170 patients below age 21 at surgery. Demographic, clinical, genetic, biological data [basal and pentagastrine-stimulated calcitonin (CT and CT/Pg, respectively)], and tumor node metastasis (TNM) status were collected. DFS was assessed based on basal CT levels. Kaplan-Meier curves, Cox regression, and logistic regression models were used to determine factors associated with DFS and TNM staging.

RESULTS

No patients with a preoperative basal CT <31 ng/ml had persistent or recurrent disease. Medullary thyroid carcinoma defined by a diameter ≥10 mm [hazard ratio (HR): 6.0; 95% confidence interval (95% CI): 1.8-19.8] and N1 status (HR: 20.8; 95% CI: 3.9-109.8) were independently associated with DFS. Class D genotype [odds ratio (OR): 48.5, 95% CI: 10.6-225.1], preoperative basal CT >30 ng/liter (OR: 43.4, 95% CI: 5.2-359.8), and age >10 (OR: 5.5, 95% CI: 1.4-21.8) were associated with medullary thyroid carcinoma ≥10 mm. No patient with a preoperative basal CT <31 ng/ml had a N1 status. Class D genotype (OR: 48.6, 95% CI: 8.6-274.1), and age >10 (OR: 4.6, 95% CI: 1.1-19.0) were associated with N1 status.

CONCLUSION

In HMTC patients, DFS is best predicted by TNM staging and preoperative basal CT level below 30 pg/ml. Basal CT, class D genotype, and age constitute key determinants to decide preoperatively timely surgery.

Adjuvant external beam radiation for medullary thyroid carcinoma

BACKGROUND

Adjuvant radiation is rarely used to treat medullary thyroid carcinoma (MTC). We hypothesized that external beam radiation therapy (EBRT) would improve overall survival (OS) in MTC patients.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database identified patients who underwent total thyroidectomy and lymph nodes excision for MTC between 1988 and 2004. The Kaplan-Meier method was used for univariate comparisons of OS. Multivariate Cox proportional hazards models controlled for gender, age, lymph node status, tumor size, extent of disease, and EBRT.

RESULTS

After 12 years, EBRT did not significantly improve OS (log rank, P < 0.14). In node-positive patients, univariate analysis demonstrated an OS benefit with EBRT (log rank, P < 0.05). In a multivariate model of node-positive patients, only increasing age (P < 0.001) and tumor size (P < 0.001) significantly influenced OS.

CONCLUSIONS

The OS benefit attributed to EBRT in node-positive patients by univariate analysis could not be duplicated when controlling for known prognostic factors.

Medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) accounts for 5-8% of all thyroid cancers. MTC is mainly sporadic in nature, but an hereditary pattern [multiple endocrine neoplasia type 2 (MEN 2)] is present in 20-30% of cases, transmitted as an autosomal-dominant trait due to germline mutations of the RET proto-oncogene. About 98% of patients with MEN 2 have germline mutations in exons 5, 8, 10, 11, 13, 14, 15 or 16 of the RET gene. The primary treatment of both hereditary and sporadic forms of MTC is total thyroidectomy and removal of all neoplastic tissue present in the neck. The therapeutic option for lymph node surgery should be dictated by the results of presurgical evaluation. After total thyroidectomy, measurements of serum calcitonin (CT) and carcinoembryonic antigen are of paramount importance in the postsurgical follow-up of patients with MTC as they reflect the presence of persistent or recurrent disease. Complete remission is demonstrated by undetectable and stimulated serum CT measurement. On the contrary, if serum CT is detectable under basal conditions or becomes detectable after stimulation, the patient is probably not cured, but imaging techniques will not demonstrate any disease until serum CT approaches levels >150 pg/ml. The tumour metastasises early to both paratracheal and lateral cervical lymph nodes. Metastases outside the neck may occur in the liver, lungs, bones and, less frequently, brain and skin. Surgery is the main treatment for local and distant metastases whenever feasible. Systemic chemotherapy with dacarbazine, 5-fluorouracil and doxorubicin (alone or in combination) has shown very limited efficacy, achieving only partial responses in the range of 10-20% and of short duration. Several kinase inhibitors are currently under evaluation and preliminary results are promising. Familial cases must be identified by searching for RET proto-oncogene mutations in the proband and in family members. Carriers of the RET gene are candidates for prophylactic thyroidectomy at different ages depending on the risk associated with the specific RET mutations.

Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant cancer syndrome with major components of medullary thyroid carcinoma (MTC), pheochromocytoma and hyperparathyroidism. The disease is caused by germline mutations of the RET proto-oncogene. Subtypes of MEN 2 include MEN 2A, MEN 2B and familial MTC (FMTC) which differ in pattern of additional lesions or--in FMTC--lack of pheochromocytoma. In 2009, after extensive review of the literature, the guidelines of the American Thyroid Association made several recommendations regarding clinical and genetic diagnostic testing and treatment options. In this article, the recently published literature is reviewed and concerns regarding future perspectives are added. In particular, a critical handling of rare DNA variants and double mutations is necessary. Up to now, mutation-specific risk profiles and mutation-associated treatment recommendations are unavailable. We emphasise the need for approved centres for treatment of patients affected by MEN 2, not only adults but young children as well. As a high level of skill is required for endoscopic adrenal-sparing surgery, surgeons should declare their expertise before operating such patients. Registry-based follow-up should be mandatory including documentation of short- and long-term outcome in order to provide valid data for future counselling of patients with MEN 2.

Constitutive RET tyrosine kinase activation in hereditary medullary thyroid cancer: clinical opportunities

The ground-breaking discovery of genotype-phenotype relationships in hereditary medullary thyroid cancer has greatly facilitated early prophylactic thyroidectomy. Its timing depends not solely on a positive gene test but, more importantly, on the type of the REarranged during Transfection (RET) mutation and its underlying mode of RET receptor tyrosine kinase activation. In the past decade, the therapeutic corridor opened by molecular information has been defined down to a remarkable level of detail. Based on mutational risk profiles, preemptive thyroidectomy is recommended at 6 months of age for carriers of highest-risk mutations, before the age of 5 years for carriers of high-risk mutations, and before the age of 5 or 10 years for carriers of least-high-risk mutations. Additional lymph node dissection may not be needed in the absence of increased preoperative basal calcitonin levels. Better comprehension of RET function should enable the design of targeted therapies for RET carriers beyond surgical cure in whom the DNA-based 'window of opportunity' has been missed.

Medullary thyroid cancer: management guidelines of the American Thyroid Association

BACKGROUND

Inherited and sporadic medullary thyroid cancer (MTC) is an uncommon and challenging malignancy. The American Thyroid association (ATA) chose to create specific MTC Clinical Guidelines that would bring together and update the diverse MTC literature and combine it with evidence-based medicine and the knowledge and experience of a panel of expert clinicians.

METHODS

Relevant articles were identified using a systematic PubMed search and supplemented with additional published materials. Evidence-based recommendations were created and then categorized using criteria adapted from the United States Preventive Services Task Force, Agency for Healthcare Research and Quality.

RESULTS

Clinical topics addressed in this scholarly dialog included: initial diagnosis and therapy of preclinical disease (including RET oncogene testing and the timing of prophylactic thyroidectomy), initial diagnosis and therapy of clinically apparent disease (including preoperative testing and imaging, extent of surgery, and handling of devascularized parathyroid glands), initial evaluation and treatment of postoperative patients (including the role of completion thyroidectomy), management of persistent or recurrent MTC (including the role of tumor marker doubling times, and treatment of patients with distant metastases and hormonally active metastases), long-term follow-up and management (including the frequency of follow-up and imaging), and directions for future research.

CONCLUSIONS

One hundred twenty-two evidence-based recommendations were created to assist in the clinical care of MTC patients and to share what we believe is current, rational, and optimal medical practice.

Medullary thyroid carcinoma identified within the first year of life in children with hereditary multiple endocrine neoplasia type 2A (codon 634) and 2B

CONTEXT

Early prophylactic thyroidectomy in patients with multiple endocrine neoplasia (MEN) type 2 offers the best chance for a normal life expectancy.

OBJECTIVE

To analyze the results of thyroidectomy performed during the first year of life in six patients with MEN 2A (codon 634) or MEN 2B (codon 918) syndrome.

DESIGN AND SETTING

A university hospital-based prospective study from 2001 to 2008.

SUBJECTS AND METHODS

Six family members affected either by MEN 2A (n=3) or MEN 2B (n=3) syndrome were identified through neonatal genetic screening.

RESULTS

Total thyroidectomy was performed at a median age of 0.8 year in the six patients, with central lymph node dissection in five. Bilateral millimetric medullary thyroid carcinoma (MTC) was found in all patients, with a unilateral lymph node micrometastasis in two of the three MEN 2B patients. Before thyroidectomy, MEN 2B patients had much higher basal serum calcitonin levels than those with MEN 2A and controls. After thyroidectomy, with a median follow-up of 3.3 years, the six patients had no evidence of persistent MTC.

CONCLUSION

Bilateral millimetric MTC may be present during the first year of life in these patients, with lymph node metastases also occurring in MEN 2B patients. These results support a total thyroidectomy at the age of about one year in MEN 2A (codon 634) children with an abnormal serum calcitonin level, and a total thyroidectomy with central neck dissection within the first weeks of life in MEN 2B patients.

Premonitory symptoms preceding metastatic medullary thyroid cancer in MEN 2B: An exploratory analysis

BACKGROUND

More than 90% of M918T carriers with multiple endocrine neoplasia type 2B (MEN 2B) harbor de novo mutations in the REarranged during Transfection (RET) protooncogene. DNA-based screening for RET germline mutations is rarely useful for early diagnosis, which thus is contingent on the clinical ascertainment of MEN 2B-specific symptoms as soon as they emerge. Little information exists about the presence of these symptoms in infancy.

METHODS

Detailed information was gathered regarding the development of MEN 2B-associated symptoms from the parents of 25 M918T RET carriers and 50 age- and sex-matched controls with the use of a disease-specific questionnaire.

RESULTS

Until the end of the study, at a median age of 16.2 (range, 0.5-34.9 years), all 25 M918T RET carriers had developed medullary thyroid cancer. By that time, 96%, 91%, 71%, 75%, and 28% of carriers displayed oral manifestations, ocular abnormalities, intestinal symptoms, musculoskeletal malformations, and pheochromocytoma, respectively. During the first year of life, fewer than 20% of carriers were found to express the typical MEN 2B phenotype, whereas 86% and 61% of these children, but none of the controls, were noted for their inability to cry tears and for constipation.

CONCLUSION

Because the classic MEN 2B phenotype is rare during the first year of life, more emphasis should be placed on the more subtle features of the syndrome. Additional studies are needed to validate the usefulness of the symptoms "inability to cry" and "constipation" for earlier diagnosis of MEN 2B.

Prognostic value of lymph node yield and metastatic lymph node ratio in medullary thyroid carcinoma

INTRODUCTION

Lymphadenectomy and thyroidectomy is standard treatment for medullary thyroid carcinoma (MTC), but the prognostic importance of the number of lymph nodes removed (lymph node yield, LNY) and the proportion of metastatic lymph nodes resected (metastatic lymph node ratio, MLNR) is unknown. We hypothesized that MTC survival is influenced by LNY and MLNR.

METHODS

Patients (N = 534) who underwent thyroidectomy with lymphadenectomy for MTC between 1988 and 2004 were identified in the Surveillance, Epidemiology, and End Results (SEER) database. The Kaplan-Meier method was used for univariate comparisons of survival for LNY and MLNR with a maximum follow-up of 12 years. Cox regression models adjusted for age, sex, extent of disease, tumor size, nodal status, LNY, and MLNR.

RESULTS

By univariate analysis, increasing LNY was associated with improved survival in all patients (P < 0.002) and node-positive patients (P < 0.001). In a multivariate analysis using LNY and MLNR as categorical variables, significant factors influencing survival included: age (P < 0.001), tumor size (P < 0.001), LNY (P = 0.007), and MLNR (P < 0.02); in node-negative patients: age (P = 0.002); in node-positive patients: age (P < 0.001), tumor size (P < 0.001), and LNY (P = 0.001). Using LNY and MLNR as continuous variables, significant factors influencing survival included: age (P < 0.001), tumor size (P < 0.001), and MLNR (P = 0.01); in node-negative patients: age (P < 0.001); in node-positive patients: age (P < 0.001) and tumor size (P < 0.001).

CONCLUSION

In patients undergoing thyroidectomy and lymphadenectomy for MTC, LNY and MLNR predict poorer survival, but their impact on survival was limited to node-positive patients and was otherwise dominated by the effects of age and extent of disease.

Chronic diarrhea and facial dysmorphism in children--a clue to men 2B syndrome: a case report

Medullary thyroid cancer (MTC) is a highly malignant tumor of the thyroid gland in children, rarely diagnosed and treated by pediatric oncologists. The authors describe a 9-year-old male who presented with facial dysmorphism and history of chronic diarrhea before being diagnosed with advanced MTC. Familiarity with its clinical variants, associated RET protooncogene mutation and its clinical implication, can lead to early identification of this aggressive tumor. To date, surgery remains the only definitive therapy, with continuing dismal prognosis in metastatic disease. However, evolving newer therapeutic strategies like tyrosine kinase inhibitors and pretargeted radioimmunotherapy (pRAIT) may provide hope to children with this aggressive tumor.

Failure to recognize multiple endocrine neoplasia 2B: more common than we think?

BACKGROUND

Multiple endocrine neoplasia 2B (MEN2B) has a classic childhood phenotypic presentation characterized by mucosal neuromas and marfanoid habitus. However, the diagnosis of MEN2B is often delayed beyond childhood, at which time medullary thyroid carcinoma (MTC) may be regionally advanced or metastatic. We examined the extent of this delay and its impact on the treatment of MTC.

METHODS

Patients in the MEN database were retrospectively analyzed to determine the age at first presentation for a MEN2B-related complaint and the subsequent time to correct diagnosis. Operative and pathology reports were reviewed to determine the extent of thyroidectomy and cervical lymphadenectomy during the initial and subsequent neck operations.

RESULTS

We identified 22 patients with MEN2B, 20 were de novo cases and a M918T RET gene mutation was confirmed in 18 of the 22 patients. Median age at diagnosis of MTC was 13 years (range 6-25 years). The median delay in diagnosis was 26 months (range 0-18 years). Persistent local-regional MTC was present following the initial cervical operation in 12 of 22 patients (55%); including 4 of 13 with MEN2B diagnosed prior to initial surgery and 8 of 9 with MEN2B diagnosed after initial surgery.

CONCLUSIONS

Most patients displayed phenotypic characteristics of MEN2B long before the correct diagnosis was made. Half of the patients failed to undergo complete resection of MTC at their initial thyroid surgery. Early recognition of the MEN2B phenotype with a thoughtful approach to preoperative staging and surgery will maximize control of MTC and minimize the need for reoperation.

RET proto-oncogene mutations are restricted to codons 634 and 918 in mainland Chinese families with MEN2A and MEN2B

OBJECTIVE

Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene, which includes multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). In this paper we present the phenotype-genotype correlation of 20 unrelated Chinese families with 15 cases of MEN2A and five cases of MEN2B.

DESIGN

Cross-sectional study.

PATIENTS

A total of 147 members from the 20 families were included. Among them, 119 family members were from MEN2A pedigrees (including 15 MEN2A probands) and 28 members from MEN2B pedigrees (including five MEN2B probands).

MEASUREMENTS

Genomic DNA was isolated from peripheral blood leucocytes and was amplified using polymerase chain reaction (PCR). DNA analysis for RET mutations in exons 8, 10, 11, 13, 14, 15 and 16 was performed with specific primers.

RESULTS

Thirty-seven MEN2A and five MEN2B patients were identified as having RET mutations. The incidence of medullary thyroid carcinoma (MTC), pheochromocytoma (PCC) and hyperparathyroidism (HPT) in the 37 MEN2A patients was 91.9, 56.8 and 10.8%, respectively; the onset of MTC in MEN2A patients was earlier than that of PCC and HPT. Five germline mutations, all located at codon 634 of exon11 in the RET proto-oncogene, were detected in all of the 37 MEN2A patients. The highest frequency of the five germline mutations was C634Y (46.7%), followed by C634R (26.7%), C634W (13.3%), C634F (6.7%) and C634S (6.7%). No statistical significance was found between the incidence of PCC and different genotypes of codon 634 in MEN2A patients, whereas the incidence of HPT was closely associated with C634R and C634Y. The gene mutation (M918T) at exon16 of the RET proto-oncogene was present in five MEN2B probands.

CONCLUSIONS

RET proto-oncogene mutations were restricted to codon 634 and 918 in Chinese families with MEN2A and MEN2B. In general the genetic characteristics of these patients with MEN2A and MEN2B reflect the general pattern around the world and it remains to be determined with larger studies in China whether Chinese patients have a different genetic pattern of mutations.

Genotype-phenotype based surgical concept of hereditary medullary thyroid carcinoma

BACKGROUND

Since DNA tests have enabled reliable identification of asymptomatic RET (rearranged during transfection) gene carriers, myriads of publications have appeared on genotype-phenotype relationships. A comprehensive appraisal of this body of evidence using evidence-based methodology is pending.

METHODS

This study was based on systematic evaluation of the literature using evidence-based criteria.

RESULTS

(1) There is a distinct age-related progression of hereditary medullary thyroid carcinoma (MTC) in carriers of RET mutations (grade C). (2) Among the high-risk RET mutations, those in codon 634 cause higher penetrance rates of the multiple endocrine neoplasia 2A phenotype (MTC, pheochromocytoma, and parathyroid hyperplasia/adenoma) than mutations in codons 609, 611, 618, and 620, irrespective of the amino acid substituting for cysteine (grade C). (3) DNA-based screening is superior to calcitonin-based screening in asymptomatic RET carriers (grade C). (4) Using a worst-case scenario, i.e., considering the earliest finding of MTC in asymptomatic RET carriers, pre-emptive thyroidectomy should be performed before that time (grade C) to be truly prophylactic. Specifically, for carriers of highest-risk mutations (codon 918): within the first year of life; for carriers of high-risk mutations (codon 609, 611, 618, 620, 630, and 634): before the age of 5 years; and for carriers of least-high risk mutations (codon 768, 790, 791, 804, and 891): before the age of 5-10 years. Strict adherence to these grade C recommendations can result in undertreatment of the former (codon 634) and overtreatment of the latter.

CONCLUSIONS

These genotype-phenotype correlations provide a solid foundation on which to base surgical concepts, leaving little room for randomized controlled clinical trials.

Medullary thyroid carcinoma in a 2-month-old male with multiple endocrine neoplasia 2B and symptoms of pseudo-Hirschsprung disease: a case report

A 5-week-old male patient was seen for symptoms suggestive of Hirschsprung disease (abdominal distension, failure to thrive, and explosive defecation). Rectum biopsies revealed an intestinal ganglioneuromatosis, which is usually associated with multiple endocrine neoplasia (MEN) syndrome type 2B. The ensuing molecular genetic analysis revealed a M918T mutation of the RET protooncogene, which is associated with early-onset medullary thyroid carcinoma (MTC). Therefore, total thyroidectomy and central lymphadenectomy were performed at the age of 9 weeks. Histology showed a medullary microcarcinoma. This report of MTC occurrence within the first weeks of life underlines the importance of early diagnosis and thyroidectomy in patients with MEN 2B syndrome. Because many patients with MEN 2A and B show gastrointestinal symptoms before the development of MTC, the possibility of MEN 2 should be recognized, and genetic testing for the presence of RET mutations should be included in the explorative diagnosis for megacolon.

[Multiple endocrine neoplasia type 2]

Multiple endocrine neoplasia type 2 (MEN2) is an hereditary disease with a prevalence of 1/5000. Three phenotypic variants have been identified: MEN2A associates medullary thyroid carcinoma (MTC) to pheochromocytoma in about 20-50% of cases and to primary hyperparathyroidism in 5-20% of cases; MEN2B associates MTC to pheochromocytoma in 50% of cases, to marphanoid habitus and to mucosal and digestive ganglioneuromatosis whereas in familial isolated medullary thyroid carcinoma (FMTC), the other components of the disease are absent. In MEN2, natural history of the disease and a common embryologic origin (neural crest) may explain the phenotypes observed in the organ involved, beginning from the stage of hyperplasia to adenoma and cancer. MEN2 is an inherited autosomal dominant disease with a complete penetrance, related to germline mutation in the proto-oncogene RET. MTC represent the most frequent circumstance of diagnosis. Pheochromocytoma and HPT may reveal the disease unfrequently and are systematically associated to undiagnosed MTC which is present yet. Analysis of the RET gene allows to confirm the diagnosis of MEN2 by identifying the causal germline mutation. Management of MEN2 patients include thyroidectomy associated to cervical central and bilateral lymph nodes dissection for MTC, unilateral adrenalectomy for unilateral pheochromocytoma or bilateral adrenalectomy when both glands are involved, and selective resection of pathologic parathyroid glands for HPT. Familial genetic screening detects at risk subjects who will develop the disease and allows to manage them at the earliest stage of the disease by perform early or prophylactic thyroidectomy such giving them the best chance of cure. Prognosis of MEN2 is mainly related to the stage-dependant prognosis of MTC, thus pointing the necessity of a complete thyroid surgery for index cases with MTC and the earliest thyroidectomy for screened at risk subjects.