Multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma: an update

Targeting of RET oncogene by naphthalene diimide-mediated gene promoter G-quadruplex stabilization exerts anti-tumor activity in oncogene-addicted human medullary thyroid cancer

Medullary thyroid cancer (MTC) relies on the aberrant activation of RET proto-oncogene. Though targeted approaches (i.e., tyrosine kinase inhibitors) are available, the absence of complete responses and the onset of resistance mechanisms indicate the need for novel therapeutic interventions. Due to their role in regulation of gene expression, G-quadruplexes (G4) represent attractive targets amenable to be recognized or stabilized by small molecules. Here, we report that exposure of MTC cells to a tri-substituted naphthalene diimide (NDI) resulted in a significant antiproliferative activity paralleled by inhibition of RET expression. Biophysical analysis and gene reporter assays showed that impairment of RET expression was consequent to the NDI-mediated stabilization of the G4 forming within the gene promoter. We also showed for the first time that systemic administration of the NDI in mice xenotransplanted with MTC cells resulted in a remarkable inhibition of tumor growth in vivo. Overall, our findings indicate that NDI-dependent RET G4 stabilization represents a suitable approach to control RET transcription and delineate the rationale for the development of G4 stabilizing-based treatments for MTC as well as for other tumors in which RET may have functional and therapeutic implications.

The Clinical Spectrum of Multiple Endocrine Neoplasia Type 2A with Cutaneous Lichen Amyloidosis in Ethnic Han Chinese

This study systematically reviewed previous literatures and analyzed the genotype-phenotype relationship between the multiple endocrine neoplasia type 2A (MEN 2A)-cutaneous lichen amyloidosis (CLA) and RET/OSMR/IL31RA mutations. RET/OSMR/IL31RA screening was performed on 8 RET-carriers from 3 independent Chinese MEN 2A families. Besides, 51 MEN 2A-CLA patients in 116 RET carriers from literatures were clustered and analyzed. Our results indicated that almost all MEN 2A-CLA patients exhibited CLA which was located in the scapular region and carried RET mutation at codon 634. Meanwhile, we firstly described MEN 2A-CLA here in Chinese Han patient with RET p.C634F mutation.

Non-mammalian models of multiple endocrine neoplasia type 2

Twenty-five years ago, RET was identified as the primary driver of multiple endocrine neoplasia type 2 (MEN2) syndrome. MEN2 is characterized by several transformation events including pheochromocytoma, parathyroid adenoma and, especially penetrant, medullary thyroid carcinoma (MTC). Overall, MTC is a rare but aggressive type of thyroid cancer for which no effective treatment currently exists. Surgery, radiation, radioisotope treatment and chemotherapeutics have all shown limited success, and none of these approaches have proven durable in advanced disease. Non-mammalian models that incorporate the oncogenic RET isoforms associated with MEN2 and other RET-associated diseases have been useful in delineating mechanisms underlying disease progression. These models have also identified novel targeted therapies as single agents and as combinations. These studies highlight the importance of modeling disease in the context of the whole animal, accounting for the complex interplay between tumor and normal cells in controlling disease progression as well as response to therapy. With convenient access to whole genome sequencing data from expanded thyroid cancer patient cohorts, non-mammalian models will become more complex, sophisticated and continue to complement future mammalian studies. In this review, we explore the contributions of non-mammalian models to our understanding of thyroid cancer including MTC, with a focus on Danio rerio and Drosophila melanogaster (fish and fly) models.

Looking beyond the thyroid: advances in the understanding of pheochromocytoma and hyperparathyroidism phenotypes in MEN2 and of non-MEN2 familial forms

Over the last years, the knowledge of MEN2 and non-MEN2 familial forms of pheochromocytoma (PHEO) has increased. In MEN2, PHEO is the second most frequent disease: the penetrance and age at diagnosis depend on the mutation of RET Given the prevalence of bilateral PHEO (50% by age 50), adrenal sparing surgery, aimed at sparing a part of the adrenal cortex to avoid adrenal insufficiency, should be systematically considered in patients with bilateral PHEO. Non-MEN2 familial forms of PHEO now include more than 20 genes: however, only small phenotypic series have been reported, suggesting that phenotypic features of isolated hereditary PHEO must be better explored, and follow-up series are needed to better understand the outcome of patients carrying mutations of these genes. The first part of this review will mainly focus on these points. In the second part, a focus will be given on MEN2 and non-MEN2 familial forms of hyperparathyroidism (HPTH). Again, the management of MEN2 HPTH should be aimed at curing the disease while preserving an optimal quality of life by a tailored parathyroidectomy. The phenotypes and outcome of MEN1-, MEN4- and HRPT2-related HPTH are briefly described, with a focus on the most recent literature data and is compared with familial hypocalciuric hypercalcemia.

Novel targeted therapeutics for MEN2

The rearranged during transfection (RET) proto-oncogene was recognized as the multiple endocrine neoplasia type 2 (MEN2) causing gene in 1993. Since then, much effort has been put into a clear understanding of its oncogenic signaling, its biochemical function and ways to block its aberrant activation in MEN2 and related cancers. Several small molecules have been designed, developed or redirected as RET inhibitors for the treatment of MEN2 and sporadic MTC. However, current drugs are mostly active against several other kinases, as they were not originally developed for RET. This limits efficacy and poses safety issues. Therefore, there is still much to do to improve targeted MEN2 treatments. New, more potent and selective molecules, or combinatorial strategies may lead to more effective therapies in the near future. Here, we review the rationale for RET targeting in MEN2, the use of currently available drugs and novel preclinical and clinical RET inhibitor candidates.

Advances in risk-oriented surgery for multiple endocrine neoplasia type 2

Genetic association studies hinge on definite clinical case definitions of the disease of interest. This is why more penetrant mutations were overrepresented in early multiple endocrine neoplasia type 2 (MEN2) studies, whereas less penetrant mutations went underrepresented. Enrichment of genetic association studies with advanced disease may produce a flawed understanding of disease evolution, precipitating far-reaching surgical strategies like bilateral total adrenalectomy and 4-gland parathyroidectomy in MEN2. The insight into the natural course of the disease gleaned over the past 25 years caused a paradigm shift in MEN2: from the removal of target organs at the expense of greater operative morbidity to close biochemical surveillance and targeted resection of adrenal tumors and hyperplastic parathyroid glands. The lead time provided by early identification of asymptomatic MEN2 carriers under biochemical surveillance delimits a 'window of opportunity', within which (i) pre-emptive total thyroidectomy alone is adequate, circumventing morbidity attendant to central node dissection; (ii) subtotal 'tissue-sparing' adrenalectomy is sufficient, trading the risk of steroid dependency for the risk of a second pheochromocytoma in the adrenal remnant and (iii) parathyroidectomy is limited to enlarged glands, trading the risk of postoperative hypoparathyroidism for the risk of leaving behind hyperactive parathyroid glands. Future research should delineate further the mutation-specific, age-dependent penetrance of pheochromocytoma and primary hyperparathyroidism to refine the risk-oriented approach to MEN2. The sweeping changes in the management of MEN2 since the new millenium hold the hope that death and major morbidity from this uncommon disease can be eliminated in our lifetime.

Advances in the management of MEN2: from improved surgical and medical treatment to novel kinase inhibitors

Medullary thyroid carcinoma (MTC), a tumor derived from the neural crest, occurs either sporadically or as the dominant component of the type 2 multiple endocrine neoplasia (MEN) syndromes, MEN2A and MEN2B. The discovery that mutations in the RET protooncogene cause hereditary MTC was of great importance, since it led to the development of novel methods of diagnosis and treatment. For example, the detection of a mutated RET allele in family members at risk for inheriting MEN2A or MEN2B signaled that they would develop MTC, and possibly other components of the syndromes. Furthermore, the detection of a mutated allele created the opportunity, especially in young children, to remove the thyroid before MTC developed, or while it was confined to the gland. The discovery also led to the development of molecular targeted therapeutics (MTTs), mainly tyrosine kinase inhibitors, which were effective in the treatment of patients with locally advanced or metastatic MTC. While responses to MTTs are often dramatic, they are highly variable, and almost always transient, because the tumor cells become resistant to the drugs. Clinical investigators and the pharmaceutical industry are focusing on the development of the next generation of MTTs, which have minimal toxicity and greater specificity for mutated RET.

Thyroid Cancer: Risk-Stratified Management and Individualized Therapy

Thyroid cancer is the most common endocrine malignancy. Differentiated thyroid cancer (DTC) with the two subtypes, papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC), is the most frequent subtype of thyroid cancer; more rare subtypes are medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC). The incidence of DTC has increased rapidly in recent years due to the more frequent use of imaging methods such as ultrasound of the neck and fine-needle aspiration (FNA) of thyroid nodules. After total thyroidectomy and radioiodine treatment, DTC remains an indolent and curable disease in most patients, whereas the cure rate in MTC is lower and depends on early diagnosis. Most ATCs are incurable. In recent years, there has been great progress in identifying genetic changes in thyroid cancer, and genetic testing of FNA samples or blood samples provides useful information for clinical decision making. Tumor staging, either postoperatively or by imaging, and measuring the tumor markers thyroglobulin for DTC and calcitonin for MTC, allow for dynamic risk-adapted stratification for follow-up procedures. In advanced metastatic thyroid cancer, molecular targeted therapy using tyrosine kinase receptor inhibitors, including sorafenib, lenvantinib, vandetanib, and cabozantinib, helps control tumor progression and prolongs progression-free survival. Using a dynamic risk-stratified approach to manage thyroid cancer, the outcomes for most thyroid cancer patients are excellent compared with those for other cancers. The major challenge in the future is to identify high-risk patients and to treat and monitor them appropriately. Clin Cancer Res; 22(20); 5012-21. ©2016 AACR SEE ALL ARTICLES IN THIS CCR FOCUS SECTION, "ENDOCRINE CANCERS REVISING PARADIGMS".

Generation of Adrenal Chromaffin-like Cells from Human Pluripotent Stem Cells

Adrenomedullary chromaffin cells are catecholamine (CA)-producing cells originating from trunk neural crest (NC) via sympathoadrenal progenitors (SAPs). We generated NC and SAPs from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) in vitro via BMP2/FGF2 exposure, ascertained by qPCR and immunoexpression of SOX10, ASCL1, TFAP2α, and PHOX2B, and by fluorescence-activated cell sorting selection for p75NTR and GD2, and confirmed their trunk-like HOX gene expression. We showed that continuing BMP4 and curtailing FGF2 in vitro, augmented with corticosteroid mimetic, induced these cells to upregulate the chromaffin cell-specific marker PNMT and other CA synthesis and storage markers, and we demonstrated noradrenaline and adrenaline by Faglu and high-performance liquid chromatography. We showed these human cells' SAP-like property of migration and differentiation into cells expressing chromaffin cell markers by implanting them into avian embryos in vivo and in chorio-allantoic membrane grafts. These cells have the potential for investigating differentiation of human chromaffin cells and for modeling diseases involving this cell type.

Medullary Thyroid Carcinoma With Exon 2 p.L56M RET Variant: Clinical Particular Features in Two Patients

RET (REarranged during Transfection) proto-oncogene variants are essential for the development of familial and sporadic forms of medullary thyroid carcinoma (MTC). The most frequent variants are usually located in exons 10, 11, and 13 through 16 of the RET gene. We report two cases of apparently sporadic MTC associated with the variant in exon 2 of RET gene. Patient 1, a 62-year old man who had undergone adrenalectomy for a 5 cm pheochromocytoma, was screened for type 2 multiple endocrine neoplasia (MEN 2) which showed elevated basal and post-intravenous calcium gluconate calcitonin levels. A fine needle aspiration biopsy (FNAB) confirmed the suspicion of MTC. The patient underwent total thyroidectomy and lymphadenectomy, and the histology showed C-cell hyperplasia with medullary microcarcinoma. Patient 2, a 57 years old woman, underwent total thyroidectomy for toxic multinodular goiter. Pre-operative FNAB had shown benign features, while basal calcitonin levels were only borderline increased. Final histology revealed medullary multifocal microcarcinoma. Genetic testing for RET protoncogene on DNA extracted from peripheral blood was performed in both patients and a missense variant on exon 2 (c.166C>A, p.L56M) was identified. To our knowledge, these are the first time two cases of MTC associated to RET p.L56M variant. Interestingly, one patient had also a pheochromocytoma suggesting a possible pathogenetic role of this variant in the genesis of MEN2A. While the association of this variant with MTC or MEN2A has been never reported, it has been described in association with Hirschsprung's disease.

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.

Recent advances in the biology and therapy of medullary thyroid carcinoma

Medullary thyroid cancer (MTC) is a relatively uncommon yet prognostically significant thyroid cancer. Several recent advances in the biology and current or potential treatment of MTC are notable. These include a new understanding of the developmental biology of the thyroid C cell, which heretofore was thought to develop from the neural crest. RET, encoded by the most common driver gene in MTC, has been shown to be a dual function kinase, thus expanding its potential substrate repertoire. Promising new therapeutic developments are occurring; many have recently progressed to clinical development. There are new insights into RET inhibitor therapy for MTC. New strategies are being developed to inhibit the RAS proteins, which are potential therapeutic targets in MTC. Potential emerging immunotherapies for MTC are discussed. However, gaps in our knowledge of the basic biology of the C cell, its transformation to MTC, and the mechanisms of resistance to therapy impede progress; further research in these areas would have a substantial impact on the field.

Whole exome sequencing identifies a germline MET mutation in two siblings with hereditary wild-type RET medullary thyroid cancer

Whole exome sequencing (WES) was used to investigate two Italian siblings with wild-type RET genotype, who developed medullary thyroid cancers (MTCs) and, later, primary prostate and breast cancers, respectively. The proband's MTC harbored a p.Met918Thr RET mutation; his sister's MTC was RET/RAS wild-type. Both siblings had a germline mutation (p.Arg417Gln) in the extracellular Sema domain of the proto-oncogene MET. Experiments involving ectopic expression of MET p.Arg417Gln in MET-negative T47D breast cancer cells documented the mutant receptor's functionality and its ability to enhance cell migration and invasion. Our findings highlight a possible link between MET germline mutations and MTCs and suggest that MET p. Arg417Gln may promote an invasive malignant phenotype. The possibility that MTC can be driven/co-driven by a MET mutation has potential management implications, since the tyrosine-kinase inhibitor cabozantinib-approved for treating advanced MTCs-is a specific MET inhibitor.

When should genetic testing be performed in patients with neuroendocrine tumours?

Neuroendocrine tumours (NETs) are a heterogenous group of tumours arising from neuroendocrine cells in several sites around the body. They include tumours of the gastroenteropancreatic system, phaeochromocytoma and paraganglioma and medullary thyroid cancer. In recent years, it has become increasingly apparent that a number of these tumours arise as a result of germline genetic mutations and are inherited in an autosomal dominant pattern. The number of genes implicated is increasing rapidly. Identifying which patients are likely to have a germline mutation enables clinicians to counsel patients adequately about their future disease risk, and allows for earlier detection of at-risk patients through family screening. The institution of screening and surveillance programmes may in turn lead to a major shift in presentation patterns for some of these tumours. In this review, we examine the features which may lead a clinician to suspect that a patient may have an inherited cause of a NET and we outline which underlying conditions should be suspected. We also discuss what type of screening may be appropriate in a variety of situations.

Transcriptional landscape of a RETC634Y-mutated iPSC and its CRISPR-corrected isogenic control reveals the putative role of EGR1 transcriptional program in the development of multiple endocrine neoplasia type 2A-associated cancers

MEN2A is a hereditary cancer-predisposing syndrome that affects patients with germline RET mutations. The effects of this oncogenic tyrosine kinase in the context of primitive stem cells are not known. In order to study these events, we generated a MEN2A induced Pluripotent Stem Cell (iPSC) line from a patient with RET mutation and an isogenic counterpart by CRISPR-Cas9 correction of the mutation. Whole exome sequencing of iPSC before and after CRISPR-Cas9 genome edition revealed no major exonic off target effect of the CRISPR correction. However, an integrative differential gene expression analysis of iPSC with oncogenic RET^C634Y and its gene-corrected iPSC with RET^Y634C as well as RET^wt iPSCs revealed activation of the Early Growth Response 1 (EGR1) transcriptional program in RET-mutated iPSC, a pathway shown to be involved in RET-induced oncogenesis. These data constitute the first proof of concept of the feasibility of the use of an iPSC and its genome-corrected counterpart to unravel the molecular mechanisms underlying the development of the hereditary MEN2A cancer predisposing syndrome.

Integrating surgery and genetic testing for the modern surgeon

The field of cancer genetics is rapidly evolving and several genetic mutations have been identified in hereditary cancer syndromes. These mutations can be diagnosed via routine genetic testing allowing prompt intervention. This is especially true for certain variants of colorectal, breast, and thyroid cancers where genetic testing may guide surgical therapy. Ultimately, surgical intervention may drastically diminish disease manifestation or progression in individuals deemed as high-risk based on their genetic makeup. Understanding the concepts of gene-based testing and integrating into current surgical practice is crucial. This review addresses common genetic syndromes, tests, and interventions salient to the current surgeon.

CXCR4/CXCR7/CXCL12 axis promotes an invasive phenotype in medullary thyroid carcinoma

Background:

Medullary thyroid carcinoma (MTC) is a rare and challenging endocrine malignancy. Once spread, the therapeutic options are limited and the outcome poor. For these patients, the identification of new druggable biological markers is of great importance. Here, we investigated the prognostic and biological role of the C-X-C chemokine receptors type 4 and 7 (CXCR4/7) in MTC.

Methods:

Eighty-six MTC and corresponding non-neoplastic thyroid specimens were immunohistochemically stained for CXCR4/7 using tissue microarray technology and expression levels correlated with clinicopathological variables. Medullary thyroid carcinoma cell line TT was treated with recombinant human SDF1α/CXCL12 (rh-SDF1α) and CXCR4 antagonists AMD3100 and WZ811. Changes in cell cycle activation, tumour cell invasiveness as well as changes in mRNA expression levels of genes associated with epithelial–mesenchymal transition (EMT) were investigated.

Results:

High CXCR4 expression was associated with large tumour size and metastatic disease. CXCR4 antagonists significantly reduced tumour cell invasiveness, while the treatment with rh-SDF1α stimulated invasive growth, caused cell cycle activation and induced EMT.

Conclusions:

The CXCR4/CXCR7/CXCL12 axis plays an important role in MTC. We provide first evidence that the chemokine receptors might serve as potential therapeutic targets in patients with advanced MTC and offer new valuable insight into the underlying molecular machinery of metastatic MTC.

Familial MTC with RET exon 8 Gly533Cys mutation: origin and prevalence of second malignancy

INTRODUCTION

High prevalence of RET p.Gly533Cys (c.1597G > T) has been found in familial MTC in Greece (exon 8 fMTC). We studied their origin and compared clinical characteristics with non-exon 8 fMTC.

METHODS

102 fMTC (FMTC and MEN2A) patients (31.4% males) were followed for 2.9-37 years (median 6 years). Fifty-one carried the RET exon 8 mutation; the remaining were non-exon 8 fMTC (exons 10, 11, 13, 14). Pre-, post-operative calcitonin, disease extent at diagnosis and follow-up and families' place of origin were recorded.

RESULTS

Exon 8 fMTC were older (42.3 ± 13.3 vs 30.8 ± 17.8 years, P < 0.001), including index cases (P = 0.016). In index cases, the stage at diagnosis was more favorable in exon 8 fMTC compared to non-exon 8 fMTC (stage I and II: 65% vs 23.8%, stage III: 25% vs 57.1%, stage IV: 10% vs 19%, P = 0.025). More favorable outcome was noted in exon 8 fMTCs (remission: 72.5% vs 45.8%, stable disease: 27.5% vs 41.7%, progression: 0.0% vs 12.5%, P = 0.001). Exon 8 fMTC patients carried more frequently a second malignancy (25.5% vs 6.3%, P = 0.009); 69% of these were PTCs. Exon 8 fMTC patients were significantly older at diagnosis compared to non-exon 8 moderate-risk RET carriers and presented more favorable clinical outcome (remission: 72.5% vs 50%, stable disease: 27.5% vs 41.7%, progression: 0.0% vs 8.3%, P = 0.021). This difference remained when only index cases were analyzed. 'Hot spots' in the origin of exon 8 fMTCs families were recognized. No phenotype or outcome differences were found between the exon 8 families from the various regions.

CONCLUSIONS

In exon 8 fMTCs' older age, favorable disease stage at diagnosis and favorable outcome suggest slow disease progression compared to non-exon 8 fMTC. Compared with moderate-risk RET mutation carriers, exon 8 fMTC patients have a more favorable clinical outcome. The higher prevalence of second malignancies, especially PTC, not previously reported, merits further investigation. Increased awareness for inherited disease is required for patients with apparently sporadic MTC originating from recognized 'hot spots', as the age at presentation is usually delayed.

Sporadic minute medullary thyroid carcinoma with a double RET mutation: A case report

We describe a 74-year-old man with a nodular goiter accompanied by an incidental sporadic minute medullary thyroid carcinoma (MTC). Histopathologically, the MTC was a well-defined 1.7 mm tumor in the upper one-third right lobe, with solid cell nests (SCNs) adjacent to the MTC. C-cells were scattered mainly around the SCNs, but C-cell hyperplasia was not evident in the background thyroid. The MTC cell phenotype was immunohistochemically identical to background C-cells, but was completely different from the SCN main cells. Direct DNA analyses of isolated MTC paraffin-embedded specimens revealed two RET proto-oncogene missense point mutations in exon 11 (i.e., C630R and C634W). The non-tumor thyroid tissue did not reveal any mutations. This study reports the smallest case of sporadic MTC with a double RET somatic mutation, substantiating that RET mutations can occur during a very early stage of carcinogenesis. The combined presence of C630R and C634W represent a novel somatic mutation in sporadic MTC. The present case indicates that the sporadic MTC originated from the surrounding C-cells of the SCNs without C-cell hyperplasia and that the SCN main cells may not be able to develop into an MTC.

A large Chinese pedigree of multiple endocrine neoplasia type 2A with a novel C634Y/D707E germline mutation in RET exon 11

The present study identified the clinical features of the largest multiple endocrine neoplasia type 2 (MEN2) A pedigree from China, with a novel double missense rearranged during transfection (RET) mutation (C634Y/D707E). To the best of our knowledge, the D707E mutation has not been identified to date. In the present study, a total of 101 family members who originated from a large pedigree (134 members in total) underwent RET mutation screening by next-generation sequencing and polymerase chain reaction (PCR) amplification, followed by direct bidirectional DNA sequencing. The clinical features of this pedigree were carefully reviewed retrospectively, and statistical analyses were conducted using SPSS software. A total of 33 (32.67%) carriers were identified to exhibit the C634Y/D707E RET germline mutation. The mean age of the patients with medullary thyroid carcinoma (MTC) identified by RET screening was 38.4±16.5 years (n=11; range, 14–65 years). Only 4 patients with pheochromocytoma with a median age of 37 years were identified. No hyperparathyroidism was diagnosed. Persistent or recurrent disease developed in the patients of the present study who underwent inappropriate initial thyroid surgeries that were performed in previous decades (III10, III23, III24, III27 and IV46, as they had undergone two surgeries prior to the present study). A total of 66.70% (6/9) of patients, following thyroidectomy, continued to develop persistent or recurrent disease during the present screening study. In total, 3 patients succumbed to MTC or distant metastasis in the present study. The increase in carcinoembryonic antigen (CEA) levels correlated with the increase in basal serum calcitonin (Ct) levels according to Pearson correlation analysis in patients with MTC without surgery. Ct and CEA levels were also significantly correlated with tumor volumes. To the best of our knowledge, the present study is the first to identify a novel double RET missense mutation in the largest MEN2A pedigree from China. Additional in-depth study is necessary to elucidate the molecular mechanisms of the D707E mutation and its potential joint effects with the other C634Y mutation in the pedigree of the present study.

Generation of an induced pluripotent stem cell line from a patient with hereditary multiple endocrine neoplasia 2B (MEN2B) syndrome with "highest risk" RET mutation

Multiple Endocrine Neoplasia Type 2B (MEN2B) is a cancer-predisposing syndrome that affects patients with germline RET mutations. The clinical spectrum of the syndrome includes medullary thyroid carcinoma (MTC) and pheochromocytoma. Currently, there is no satisfactory model recapitulating all the features of the disease especially at the level of stem cells. We generated induced pluripotent stem cells (iPSCs) from a patient with RET mutation at codon 918 who developed pheochromocytoma and MTC. These iPSC had normal karyotype, harboured the RET^M918T mutation and expressed pluripotency hallmarks. A comprehensive pathological assessment of teratoma was performed after injection in immunodeficient mice.

Plasma Calcitonin Levels and miRNA323 Expression in Medullary Thyroid Carcinoma Patients with or without RET Mutation

Background: Medullary thyroid cancer (MTC) is an endocrine tumor featuring parafollicular or C-cell differentiation, with calcitonin as a specific biomarker in MTC diagnosis. Germline mutations in the RET proto-oncogene are considered responsible for its familial occurrence and somatic mutations can cause sporadic lesions. MicroRNAs can act as oncogenes or tumor suppressors by inhibiting the expression of target genes.. The aim of this study was to investigate relationships between plasma levels of calcitonin and miRNA323 expression in MTC patients with or without RET mutation. Methods: In this cross-sectional study, MTC lesions (based on pathological confirmation) were investigated. Genomic DNA was extracted and Exons 10 and 11 of RET were genotyped using PCR-sequencing. Division was into two groups of 43 cases each with or without mutation. Plasma levels of calcitonin were determined in both. Results: miRNA323 was measured using real-time-PCR. After performing normality tests, independent T-tests and Mann Whitney tests were used for the statistical comparison of parametric and nonparametric data, respectively. Plasma levels of calcitonin were significantly higher in MTC cases without a RET mutation compared to those with a mutation. Conclusion: There was no significant difference between the two groups regarding the expression of miRNA323 so that this parameter could not be used as a bio-index germ line mutations in MTCs. However, determination of calcitonin levels in plasma might be helpful in this regard.

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.

The molecular basis for RET tyrosine-kinase inhibitors in thyroid cancer

RET receptor tyrosine kinase acts as a mutated oncogenic driver in several human malignancies and it is over-expressed in other cancers. Small molecule compounds with RET tyrosine kinase inhibitory activity are being investigated for the targeted treatment of these malignancies. Multi-targeted compounds with RET inhibitory concentration in the nanomolar range have entered clinical practice. This review summarizes mechanisms of RET oncogenic activity and properties of new compounds that, at the preclinical stage, have demonstrated promising anti-RET activity.

Clinical and pathological analysis of 19 cases of medullary thyroid carcinoma without an increase in calcitonin

BACKGROUND

Medullary thyroid carcinoma (MTC), defined as a malignant tumour with C-cell differentiation, is of neuroendocrine origin and is characterized by the synthesis and secretion of calcitonin (CT). MTC without CT secretion has been reported on rare occasions. The purpose of this study was to evaluate the histological, immunohistochemical, and molecular pathologic features as well as the clinical significance of non-secretory MTC (NCR-MTC).

METHODS

A retrospective analysis of patients with NCR-MTC was performed. The clinical features of NCR-MTC, including age, gender, tumour size and number, clinical signs of hypocalcaemia and diarrhoea, and the presence of lymph node metastasis, as well as the pathologic features of the disease, including tumour morphology, presence of neuroendocrine structures, capsular invasion, and immunohistochemical expression and presence of mutations in the RET gene, were evaluated.

RESULTS

Nineteen patients with NCR-MTC were identified among 158 patients with MTC, resulting in a prevalence rate of 12.02%. Patients with NCR-MTC typically had masses less than 1cm in size (73.7%, 14/19). Hypocalcaemia was not present in 94.7% (18/19) of patients. While 42.1% (8/19) of patients with NCR-MTC did not have amyloid deposits, only 18% (25/139) of patients with secretory MTC did not have such deposits. While 95.7% (133/139) of the control group of patients with secretory MTC had neuroendocrine tumour structure, only 84.2% (16/19) of the patients with NCR-MTC had this type of tumour structure. Patients with NCR-MTC were also less likely to have vascular tumour thrombus, lymph node metastasis or thyroid capsular invasion. With regard to immunohistochemistry, CT expression was mostly negative, and carcinoembryonic antigen (CEA) expression was positive in 21.1% (4/19) of patients with NCR-MTC, while only 5.8% (8/139) of patients in the control group had positive CEA expression.

CONCLUSIONS

The prevalence of NCR-MTC was low (12.02%). This type of tumour was smaller in size and more differentiated. Compared with the control group, relatively few patients had obvious symptoms, hypocalcaemia, lymph node metastasis, thyroid capsular or vascular invasion, or tumours with amyloid or neuroendocrine tumour structure.

Assessment of Depression, Anxiety, Quality of Life, and Coping in Long-Standing Multiple Endocrine Neoplasia Type 2 Patients

BACKGROUND

Data on psychological harm in multiple endocrine neoplasia type 2 (MEN2) are scarce.

OBJECTIVES

The aim of this study was to assess anxiety, depression, quality of life, and coping in long-standing MEN2 patients.

PATIENTS AND METHODS

Patients were 43 adults (age ≥18 years) with clinical and genetic diagnosis of MEN2 and long-term follow-up (10.6 ± 8.2 years; range 1-33 years). This was a cross-sectional study with qualitative and quantitative psychological assessment using semi-directed interviews and HADS, EORTC QLQ C30, and MINI-MAC scales. Adopting clinical criteria from 2015 ATA Guidelines on MEN2, biochemical cure (39%; 16/41), persistence/recurrence (61%; 25/41), and stable chronic disease (22/41) of medullary thyroid carcinoma (MTC) were scored. Pheochromocytoma affected 19 (44%) patients, with previous adrenalectomy in 17 of them.

RESULTS

Overall, anxiety (42%; mean score 11 ± 2.9; range 8-18; anxiety is defined as a score ≥8) and depression (26%; mean score 11 ± 3.8; range 8-20; depression is defined as a score ≥8) symptoms were frequent. Patients who transmitted RET mutations to a child had higher scores for weakness-discouragement/anxious preoccupation and lower scores for cognitive, emotional, and physical functioning (p < 0.05). Feelings of guilt were present in 35% of patients with mutation-positive children. Lower mean score values for depression and anxiety and higher scores for role, cognitive, and emotional functioning were noticed in 33 patients who were well-informed about their disease (p < 0.05). Fighting spirit was more frequently found in patients with multiple surgical procedures (p = 0.019) and controlled chronic adrenal insufficiency (p = 0.024). Patients with MEN2-related stress-inducing factors had lower scores for fighting spirit and cognitive functioning and higher scores for insomnia and dyspnea (p < 0.05). Eleven patients required sustained psychotherapeutic treatment. Mean global health status was relatively good in MEN2 cases (68.1 ± 22.3), and the cured group had higher physical functioning (p = 0.021).

CONCLUSIONS

Psychological distress is likely chronic in MEN2 patients. This study identified diverse MEN2-related factors (degree of information on disease, mutation-positive children, number of surgeries, comorbidities, stress-inducing factors, and cure) interfering positively or negatively with the results of the psychometrics scales. The active investigation of these factors and the applied psychological assessment protocol are useful to identify MEN2 patients requiring psychological assistance.

Oncogenesis of Thyroid Cancer

Thyroid neoplasms encompass a variety of lesions that range from benign adenomas to malignancies. These latter can be well-differentiated, poorly differentiated or undifferentiated (anaplastic) carcinomas. More than 95% of thyroid cancers are derived from thyroid follicular cells, while 2-3% (medullary thyroid cancers, MTC) originate from calcitonin producing C-cells. Over the last decade, investigators have developed a clearer understanding of genetic alterations underlying thyroid carcinogenesis. A number of point mutations and translocations are involved, not only in its tumorigenesis, but also as have potential use as diagnostic and prognostic indicators and therapeutic targets. Many occur in genes for several important signaling pathways, in particular the mitogen-activated protein kinase (MAPK) pathway. Sporadic (isolated) lesions account for 75% of MTC cases, while inherited MTC, often in association with multiple endocrine neoplasia (MEN) type 2A and 2B syndromes, constitute the remainder. However, non-MEN familial MTC may also occur. Advances in genetic testing have revolutionized the management of MTC, with prospects of genetic screening, testing and early prophylactic thyroidectomy. Ethical concerns of these advances are addressed.

Metabologenomics of Phaeochromocytoma and Paraganglioma: An Integrated Approach for Personalised Biochemical and Genetic Testing

The tremendous advances over the past two decades in both clinical genetics and biochemical testing of chromaffin cell tumours have led to new considerations about how these aspects of laboratory medicine can be integrated to improve diagnosis and management of affected patients. With germline mutations in 15 genes now identified to be responsible for over a third of all cases of phaeochromocytomas and paragangliomas, these tumours are recognised to have one of the richest hereditary backgrounds among all neoplasms. Depending on the mutation, tumours show distinct differences in metabolic pathways that relate to or even directly impact clinical presentation. At the same time, there has been improved understanding about how catecholamines are synthesised, stored, secreted and metabolised by chromaffin cell tumours. Although the tumours may not always secrete catecholamines it has become clear that almost all continuously produce and metabolise catecholamines. This has not only fuelled changes in laboratory medicine, but has also assisted in recognition of genotype-biochemical phenotype relationships important for diagnostics and clinical care. In particular, differences in catecholamine and energy pathway metabolomes can guide genetic testing, assist with test interpretation and provide predictions about the nature, behaviour and imaging characteristics of the tumours. Conversely, results of genetic testing are important for guiding how routine biochemical testing should be employed and interpreted in surveillance programmes for at-risk patients. In these ways there are emerging needs for modern laboratory medicine to seamlessly integrate biochemical and genetic testing into the diagnosis and management of patients with chromaffin cell tumours.

Differences in the transcriptome of medullary thyroid cancer regarding the status and type of RET gene mutations

Medullary thyroid cancer (MTC) can be caused by germline mutations of the RET proto-oncogene or occurs as a sporadic form. It is well known that RET mutations affecting the cysteine-rich region of the protein (MEN2A-like mutations) are correlated with different phenotypes than those in the kinase domain (MEN2B-like mutations). Our aim was to analyse the whole-gene expression profile of MTC with regard to the type of RET gene mutation and the cancer genetic background (hereditary vs sporadic). We studied 86 MTC samples. We demonstrated that there were no distinct differences in the gene expression profiles of hereditary and sporadic MTCs. This suggests a homogeneous nature of MTC. We also noticed that the site of the RET gene mutation slightly influenced the gene expression profile of MTC. We found a significant association between the localization of RET mutations and the expression of three genes: NNAT (suggested to be a tumour suppressor gene), CDC14B (involved in cell cycle control) and NTRK3 (tyrosine receptor kinase that undergoes rearrangement in papillary thyroid cancer). This study suggests that these genes are significantly deregulated in tumours with MEN2A-like and MEN2B-like mutations; however, further investigations are necessary to demonstrate any clinical impact of these findings.

Detection of Molecular Alterations in Medullary Thyroid Carcinoma Using Next-Generation Sequencing: an Institutional Experience

Medullary thyroid carcinoma (MTC) harbors rearranged during transfection (RET) gene and rarely RAS gene mutations. The knowledge of the type of gene mutation in MTC is important to determine the treatment of the patients and the management of their family members. Targeted next-generation sequencing with a panel of 47 genes was performed in a total of 12 cases of sporadic (9/12) and hereditary MTC (3/12). Two of three hereditary MTCs had RET/C634R mutation, while the other one harbored two RET mutations (L790F and S649L). All the sporadic MTC had RET/M918T mutation except one case with HRAS mutation. Next-generation sequencing (NGS) can provide comprehensive analysis of molecular alterations in MTC in a routine clinical setting, which facilitate the management of the patient and the family members.

M918V RET mutation causes familial medullary thyroid carcinoma: study of 8 affected kindreds

Germline mutations in codon 918 of exon 16 of the RET gene (M918T) are classically associated with multiple endocrine neoplasia type 2B (MEN 2B) with highly aggressive medullary thyroid cancer (MTC), pheochromocytoma and a unique phenotype. The objectives of this study are to describe the rare M918V RET mutation discovered in 8 MTC kindreds from Brazil lacking the MEN 2B phenotype classically observed in M918T patients and to investigate the presence of a founder effect for this germline mutation. Eight apparently sporadic MTC cases were diagnosed with the germline M918V RET mutation. Subsequently, their relatives underwent clinical and genetic assessment (n = 113), and M918V was found in 42 of them. Until today, 20/50 M918V carriers underwent thyroidectomy and all presented MTC/C-cell hyperplasia; the remainder carriers are on clinical follow-up. None of the M918V carriers presented clinical features of MEN 2B. Their clinical presentation was heterogeneous, and the age at tumor diagnosis ranged from 24 to 59 years. Lymph node metastases were present in 12/20 patients, and presumable distant metastases in 2/20; in contrast, we observed a carrier of up to 87 years of age without evidence of MTC. Ethnographic fieldwork and haplotype analyses suggested that the founder mutation first settled in that area fifteen generations ago and originated from Portugal. Our study is the first to demonstrate the RET M918V mutation co-segregating in 8 familial MTC kindreds with validated evidence of a founder effect. We suggest that M918V MTC should be clinically considered an American Thyroid Association (ATA) moderate-risk category.

Systemic treatment and management approaches for medullary thyroid cancer

Although rare, medullary thyroid cancer (MTC) exemplifies the value that ever-expanding knowledge of molecular pathways and mechanisms brings to managing challenging cancers. Although surgery can be curative for MTC in many patients, a substantial proportion of patients present with locoregional or distant metastatic disease. Once distant disease occurs, treatment options are limited, and conventional cancer treatments such as cytotoxic chemotherapy are of minimal benefit. Biomarkers such as calcitonin and carcinoembryonic antigen are important correlates of disease burden as well as predictors of disease progress, including recurrence and survival. MTC is either sporadic (∼75%) or inherited (∼25%) as an autosomal dominant disease. Regardless, germline and somatic mutations, particularly in the rearranged during transfection (RET) proto-oncogene, are key factors in the neoplastic process. Gain-of-function RET mutations result in overactive proteins that lead to abnormal activation of downstream signal transduction pathways, resulting in ligand-independent growth and resistance to apoptotic stimuli. Specific RET mutation variants have been found to correlate with phenotype and natural history of MTC with some defects portending a more aggressive clinical course. Greater understanding of the consequence of the aberrant signaling pathway has fostered the development of targeted therapies. Two small-molecule tyrosine kinase inhibitors, vandetanib and cabozantinib, are currently available as approved agents for the treatment of advanced or progressive MTC and provide significant increases in progression-free survival. Since there have been no head-to-head comparisons, clinicians often select between these agents on the basis of familiarity, patient characteristics, comorbidities, and toxicity profile.

Minimally Invasive Parathyroidectomy Versus Bilateral Neck Exploration for Primary Hyperparathyroidism

Primary hyperparathyroidism is a disease that is caused by excess parathyroid hormone (PTH) secretion from 1 or more of the parathyroid glands. Surgery is the only cure. Traditional surgical management consists of a 4-gland cervical exploration. Development of imaging specific to identification of parathyroid glands and application of the rapid PTH assay to operative management have made more minimal exploration possible. There are distinct advantages and disadvantages of minimally invasive parathyroidectomy (MIP) and bilateral neck exploration (BNE). The advantages of MIP seem to outweigh those of BNE, and MIP has replaced BNE as the operation of choice by many surgeons.

RET mutation p.S891A in a Chinese family with familial medullary thyroid carcinoma and associated cutaneous amyloidosis binding OSMR variant p.G513D

There are no reports on the relationship between familial medullary thyroid carcinoma (FMTC) associated with cutaneous amyloidosis (CA) and RET or OSMR/IL31RA gene mutations. In this study, we investigated a Chinese family with FMTC/CA and found a recurrent RET c.2671T>G (p.S891A) mutation in six of 17 family members. Three of the six p.S891A mutation carriers presented with medullary thyroid carcinoma (MTC). Of them, three (two with and one without MTC) were diagnosed as having combined lichen/macular biphasic CA. We also identified a novel RET variant, c.1573C>T (p.R525W) in five members. Of them, three carriers had no evidence of thyroid/skin or basal serum/stimulated calcitonin abnormalities. In vitro cell proliferation assay indicated that oncogenic activity of RET p.S891A was slightly enhanced by p.R525W, whereas p.R525W alone had no effect on cell proliferation. Meanwhile, we identified a novel OSMR variant, c.1538G>A (p.G513D) in seven members. We noticed that three OSMR p.G513D carriers presenting with CA also had the RET p.S891A mutation. Our investigation indicated that the RET p.S891A mutation combined with OSMR p.G513D may underlie a novel phenotype manifesting as FMTC and CA.

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.

GEP- NETS UPDATE: Genetics of neuroendocrine tumors

Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms, arising from neuroendocrine cells that are dispersed throughout the body. Around 20% of NETs occur in the context of a genetic syndrome. Today there are at least ten recognized NET syndromes. This includes the classical syndromes: multiple endocrine neoplasias types 1 and 2, and von Hippel-Lindau and neurofibromatosis type 1. Additional susceptibility genes associated with a smaller fraction of NETs have also been identified. Recognizing genetic susceptibility has proved essential both to provide genetic counseling and to give the best preventive care. In this review we will also discuss the knowledge of somatic genetic alterations in NETs. At least 24 genes have been implicated as drivers of neuroendocrine tumorigenesis, and the overall rates of genomic instability are relatively low. Genetic intra-tumoral, as well as inter-tumoral heterogeneity in the same patient, have also been identified. Together these data point towards the common pathways in NET evolution, separating early from late disease drivers. Although knowledge of specific mutations in NETs has limited impact on actual patient management, we predict that in the near future genomic profiling of tumors will be included in the clinical arsenal for diagnostics, prognostics and therapeutic decisions.

Medullary thyroid carcinoma: a review on ethical considerations in treatment of children

Thyroid carcinoma is the most common malignancy of the endocrine system and it accounts approximately 1%-3% of all human cancers. Among the three subtypes of thyroid cancers, medullary thyroid carcinoma (MTC) is the most common cause of death in patients with multiple endocrine neoplasia (MEN) type 2A (MEN2A), MEN type 2B (MEN2B) and familial medullary thyroid carcinoma (FMTC). Generally, MTC accounts for up to 10% of all types of thyroid cancers. It is one of the aggressive forms of thyroid carcinoma which is manifested in childhood ages more than adults, and it comprises about 17% of all pediatric thyroid cancer. Like the other cancers, prevention of MTC is easier than its cure. In the recent decades (from 1993) the diagnosis of asymptomatic child carrying RET mutations in the affected families by MTC, has been provided by genetic screening, and prophylactic thyroidectomy is an efficacy therapeutic procedure. On the one hand, according to near the complete penetrance of the disease and its onset in the early years of life, it is required to accelerate the protection of at-risk children with relative affected by MTC and on the other hand, there are several obstructions to MTC treatment including: 1) the proband's refusal to disclose the RET mutation genetic testing results, 2) children's vulnerability because of their inability to participate in the informed consent, and 3) the existence of conflict between physicians and children's guardian. In this review article, the recommendations and ethical issues of MTC treatment in asymptomatic and at-risk children have been summarized.

SOS1 frameshift mutations cause pure mucosal neuroma syndrome, a clinical phenotype distinct from multiple endocrine neoplasia type 2B

BACKGROUND

Mucosal neuromas, thickened corneal nerves and marfanoid body habitus are characteristic phenotypic features of multiple endocrine neoplasia type 2B (MEN2B) and often provide an early clue to the diagnosis of the syndrome. Rarely, patients present with typical physical features of MEN2B but without associated endocrinopathies (medullary thyroid carcinoma or pheochromocytoma) or a RET gene mutation; this clinical presentation is thought to represent a distinct condition termed 'pure mucosal neuroma syndrome'.

METHODS

Exome sequencing was performed in two unrelated probands with mucosal neuromas, thickened corneal nerves and marfanoid body habitus, but no MEN2B-associated endocrinopathy or RET gene mutation. Sanger sequencing was performed to confirm mutations detected by exome sequencing and to test in family members and 3 additional unrelated index patients with mucosal neuromas or thickened corneal nerves.

RESULTS

A heterozygous SOS1 gene frameshift mutation (c.3266dup or c.3248dup) was identified in each proband. Sanger sequencing showed that proband 1 inherited the c.3266dup mutation from his affected mother, while the c.3248dup mutation had arisen de novo in proband 2. Sanger sequencing also identified one further novel SOS1 mutation (c.3254dup) in one of the 3 additional index patients.

CONCLUSION

Our results demonstrate the existence of pure mucosal neuroma syndrome as a clinical entity distinct from MEN2B that can now be diagnosed by genetic testing.

A comprehensive overview of the role of the RET proto-oncogene in thyroid carcinoma

The rearranged during transfection (RET) proto-oncogene was identified in 1985 and, very soon thereafter, a rearrangement named RET/PTC was discovered in papillary thyroid carcinoma (PTC). After this discovery, other RET rearrangements were found in PTCs, particularly in those induced by radiation. For many years, it was thought that these genetic alterations only occurred in PTC, but, in the past couple of years, some RET/PTC rearrangements have been found in other human tumours. 5 years after the discovery of RET/PTC rearrangements in PTC, activating point mutations in the RET proto-oncogene were discovered in both hereditary and sporadic forms of medullary thyroid carcinoma (MTC). In contrast to the alterations found in PTC, the activation of RET in MTC is mainly due to activating point mutations. Interestingly, in the past year, RET rearrangements that were different to those described in PTC were observed in sporadic MTC. The identification of RET mutations is relevant to the early diagnosis of hereditary MTC and the prognosis of sporadic MTC. The diagnostic and prognostic role of the RET/PTC rearrangements in PTC is less relevant but still important in patient management, particularly for deciding if a targeted therapy should be initiated. In this Review, we discuss the pathogenic, diagnostic and prognostic roles of the RET proto-oncogene in both PTC and MTC.

Germline ESR2 mutation predisposes to medullary thyroid carcinoma and causes up-regulation of RET expression

Familial medullary thyroid cancer (MTC) and its precursor, C cell hyperplasia (CCH), is associated with germline RET mutations causing multiple endocrine neoplasia type 2. However, some rare families with apparent MTC/CCH predisposition do not have a detectable RET mutation. To identify novel MTC/CCH predisposition genes we undertook exome resequencing studies in a family with apparent predisposition to MTC/CCH and no identifiable RET mutation. We identified a novel ESR2 frameshift mutation, c.948delT, which segregated with histological diagnosis following thyroid surgery in family members and demonstrated loss of ESR2-encoded ERβ expression in the MTC tumour. ERα and ERβ form heterodimers binding DNA at specific oestrogen-responsive elements (EREs) to regulate gene transcription. ERβ represses ERα-mediated activation of the ERE and the RET promoter contains three EREs. In vitro, we showed that ESR2 c.948delT results in unopposed ERα mediated increased cellular proliferation, activation of the ERE and increased RET expression. In vivo, immunostaining of CCH and MTC using an anti-RET antibody demonstrated increased RET expression. Together these findings identify germline ESR2 mutation as a novel cause of familial MTC/CCH and provide important insights into a novel mechanism causing increased RET expression in tumourigenesis.

Epidemiology and Clinical Presentation of Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor originating from the thyroid C cells producing mainly calcitonin (CTN) used as tumor marker. MTC occurs either sporadic (75%) or in a hereditary form (multiple endocrine neoplasia type 2, MEN2), due to germline mutations in the RET proto-oncogene. The discovery of an MTC in a patient has several diagnostic implications involving a specific strategy: preoperative evaluation of the tumor marker CTN and the extent of the disease, classification of MTC as sporadic or hereditary by DNA testing, and screening for associated endocrinopathies in hereditary MTC. Elevated CTN is a highly sensitive and specific tumor marker for diagnosis and follow-up of MTC. CTN is directly related to the tumor mass. In patients with nodular thyroid disease, diagnosis of MTC could be made by CTN determination as an indicator of tumor burden in conjunction with fine-needle aspiration. Patients with confirmed sporadic or hereditary MTC should have a total thyroidectomy and depending on the preoperative CTN value and the extent of disease additional dissection of the lymph nodes in the central and lateral neck compartment. In MEN 2 patients diagnosed by screening, the time of prophylactic thyroidectomy depends on RET mutation and CTN level.