Multigenerational familial medullary thyroid cancer (FMTC): evidence for FMTC phenocopies and association with papillary thyroid cancer

The Growth Kinetics of Collision Nodal Metastasis from Medullary and Papillary Thyroid Carcinomas: A Case Report

INTRODUCTION

The collision of medullary (MTC) and papillary thyroid carcinoma (PTC) in the same cervical lymph node can occur, but its growth kinetics has not been reported.

CASE PRESENTATION

We report a 27-year-old male patient who had collision nodal metastases from PTC and sporadic MTC in the central compartment. This was treated with total thyroidectomy and central neck dissection. The collision nodal metastasis persisted and presented with a single sonographically enlarging central compartmental lymph node postoperatively. The volume of the collision nodal metastasis increased from 226 to 507 mm³ over the first 8 months, from 507 to 572 mm³ over the next 6 months, and from 572 to 762 mm³ over the next 31 months. The calcitonin and carcinoembryonic antigen (CEA) fluctuated in the first 19 months followed by a steady increase at a doubling time of 1.97 and 8.42 years, respectively. Unstimulated thyroglobulin remained at 0.2 ng/mL or lower during the same period while thyrotropin (TSH) was not suppressed. Revision central neck dissection performed 4.5 years later resulted in undetectable serum calcitonin, CEA of 2 ng/mL, and thyroglobulin of 0.1 ng/mL from a preoperative calcitonin of 212 ng/L, CEA of 10 ng/mL, and thyroglobulin of 0.2 ng/mL. Further structural imaging 13.5 months later revealed no evidence of disease.

DISCUSSION

The growth kinetics of collision nodal metastasis from PTC and MTC can be similar to conventional PTC and MTC. Furthermore, the growth rate of such collision nodal metastases can be slow. Guided by tumor marker doubling time and regular structural imaging, surgical salvage performed after a period of active surveillance may still result in biochemical and structural remission.

Medullary and papillary thyroid carcinomas in a patient with a C634Y mutation in the RET proto-oncogene: A case report

A 41 year old man presented with a familial history of multiple endocrine neoplasia type 2A (MEN2A) and severe hypertension. Rearranged during transfection (RET) gene sequencing confirmed a Cys634Tyr mutation of TGC to TAC. Total thyroidectomy and bilateral neck dissection were performed and the pathological assessment revealed a medullary thyroid carcinoma (MTC), 0.6 cm in size on the right side (number of lymph nodes: 0/2, 0/15, 0/12, and 0/8 in areas VI, II, III, and IV, respectively) and a papillary thyroid carcinoma (PTC), 0.2 cm in size on the left side (numbers of lymph nodes: 2/6, 0/3, 0/10, and 0/6 in areas VI, II, III, and IV, respectively). There were no pathological changes in the MTC observed in the thyroid tissues on the left side. We believe that the follow-up of patients with both MTC and PTC should utilize a combination of the respective principles for rational disease reassessment.

Multiple endocrine neoplasia type 1: analysis of germline MEN1 mutations in the Italian multicenter MEN1 patient database

PURPOSE

Multiple endocrine neoplasia type 1 (MEN1) is caused by germline inactivating mutations of the MEN1 gene. Currently, no direct genotype-phenotype correlation is identified. We aim to analyze MEN1 mutation site and features, and possible correlations between the mutation type and/or the affected menin functional domain and clinical presentation in patients from the Italian multicenter MEN1 database, one of the largest worldwide MEN1 mutation series published to date.

METHODS

The study included the analysis of MEN1 mutation profile in 410 MEN1 patients [370 familial cases from 123 different pedigrees (48 still asymptomatic at the time of this study) and 40 single cases].

RESULTS

We identified 99 different mutations: 41 frameshift [small intra-exon deletions (28) or insertions (13)], 13 nonsense, 26 missense and 11 splicing site mutations, 4 in-frame small deletions, and 4 intragenic large deletions spanning more than one exon. One family had two different inactivating MEN1 mutations on the same allele. Gastro-entero-pancreatic tumors resulted more frequent in patients with a nonsense mutation, and thoracic neuroendocrine tumors in individuals bearing a splicing-site mutation.

CONCLUSIONS

Our data regarding mutation type frequency and distribution are in accordance with previously published data: MEN1 mutations are scattered through the entire coding region, and truncating mutations are the most common in MEN1 syndrome. A specific direct correlation between MEN1 genotype and clinical phenotype was not found in all our families, and wide intra-familial clinical variability and variable disease penetrance were both confirmed, suggesting a role for modifying, still undetermined, factors, explaining the variable MEN1 tumorigenesis.

Segregation and expression analyses of hyaluronan-binding protein 2 (HABP2): insights from a large series of familial non-medullary thyroid cancers and literature review

INTRODUCTION

Recently, the G534E variant of the HABP2 gene was reported as the underlying genetic defect in a large kindred with nonsyndromic familial nonmedullary thyroid cancer (FNMTC). Nevertheless, this postulated role was not confirmed in additional cohorts. Contrasting data are also available on HABP2 expression in the thyroid.

OBJECTIVES

To investigate HABP2 as a potential susceptibility gene in a large series of 27 unrelated families with FNMTC and to test its expression in thyroid tumour and matched normal tissues.

RESULTS

Three of the 27 FNMTC families (11·1%) carried the HABP2^G534E variant. The genotyping of these families showed that HABP2^G534E does not segregate with cancer. Indeed, affected individuals not carrying HABP2^G534E were identified, and the variant was present also in members without thyroid cancer. HABP2 mRNA had a very variable expression in tissues from FNMTC, sporadic papillary thyroid cancers (PTCs) or contralateral normal tissues, by either nonquantitative or quantitative RT-polymerase chain reaction. In almost all cases, the gene appeared down- or up-regulated in tumours with respect to the corresponding normal tissue. At immunohistochemistry, HABP2 was expressed in both tumour and matched control tissues, without differences between sporadic and familial cases.

CONCLUSIONS

This study on a wide series of FNMTC indicates that the HABP2^G534E variant is frequent, but does not segregate with the disease. Nevertheless, the dysregulation of HABP2 expression found in either sporadic or familial PTCs or normal thyroid tissues is consistent with similar findings in other malignancies and could indicate a role of this gene also in thyroid cancer.

Classical point mutations of RET, BRAF and RAS oncogenes are not shared in papillary and medullary thyroid cancer occurring simultaneously in the same gland

BACKGROUND

Papillary (PTC) and medullary (MTC) thyroid carcinomas represent two distinct entities, but quite frequently, they may occur simultaneously.

AIM

To provide genetic analysis of PTC and MTC occurring in the same patient (PTC/MTC) to elucidate their origin.

METHODS

Sequencing analysis of RAS, BRAF and RET oncogenes hot spots mutations in tumoral and normal tissues of 24 PTC/MTC patients.

RESULTS

Two of 24 patients (8.3 %) were affected by familial MTC (FMTC) harboring RET germline mutations in all tissues. Eight of 22 (36.4 %) sporadic cases did not show any somatic mutation in the three tissue components. Considering the MTC component, 10/22 (45.4 %) patients did not show any somatic mutation, 7 of 22 (31.8 %) harbored the M918T RET somatic mutation and 4/22 (18.2 %) presented mutations in the H-RAS gene. In an additional case (1/22, 4.6 %), H-RAS and RET mutations were simultaneously present. Considering the PTC component, 1 of 24 (4.2 %) patients harbored the V600E BRAF mutation, 1 of 24 (4.2 %) the T58A H-RAS mutation and 1 of 24 (4.2 %) the M1T K-RAS mutation, while the remaining PTC cases did not show any somatic mutation. In one case, the MTC harbored a RET mutation and the PTC a BRAF mutation. None of the mutations found were present in both tumors.

CONCLUSIONS

To our knowledge, this is the first study analyzing a possible involvement of RET, BRAF and RAS oncogene mutations in PTC/MTC. These data clearly suggest that the classical activating mutations of the oncogenes commonly involved in the pathogenesis of PTC and MTC may not be responsible for their simultaneous occurrence.

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.

Twenty years of lesson learning: how does the RET genetic screening test impact the clinical management of medullary thyroid cancer?

OBJECTIVE

Medullary thyroid carcinoma (MTC) is a rare disease that can be inherited or sporadic; its pathogenesis is related to activating mutations in the RET gene.

DESIGN

This study describes our 20-year experience regarding RET genetic screening in MTC.

PATIENTS AND METHODS

We performed RET genetic screening in 1556 subjects, 1007 with an apparently sporadic MTC, 95 with a familial form and 454 relatives of RET-positive patients with MTC.

RESULTS

A germline RET mutation was found in 68 of 1007 (6·7%) patients with sporadic MTC, while 939 patients with MTC were negative for germline RET mutations. We then identified a total of 137 gene carriers (GC). These subjects initiated a clinical evaluation for the diagnosis of MEN 2. A total of 139 MEN 2 families have been followed: 94 FMTC, 33 MEN 2A and 12 MEN 2B. Thirty-three different germline RET mutations were identified. Codon 804 was the most frequently altered codon particularly in FMTC (32/94, 34%), while codon 634 was the most frequently altered codon in MEN 2A (31/33, 94%); MEN 2B cases were exclusively associated with an M918T mutation at exon 16.

CONCLUSIONS

Our 20-year study demonstrated that RET genetic screening is highly specific and sensitive, and it allows the reclassification as hereditary of apparently sporadic cases and the identification of GC who require an adequate follow-up. We confirmed that FMTC is the most prevalent MEN 2 syndrome and that it is strongly correlated with noncysteine RET mutations. According to these findings, a new paradigm of follow-up of hereditary MTC cases might be considered in the next future.

The modifier role of RET-G691S polymorphism in hereditary medullary thyroid carcinoma: functional characterization and expression/penetrance studies

Background

Hereditary medullary thyroid carcinoma (MTC) is caused by germ-line gain of function mutations in the RET proto-oncogene, and a phenotypic variability among carriers of the same mutation has been reported. We recently observed this phenomenon in a large familial MTC (FMTC) family carrying the RET-S891A mutation. Among genetic modifiers affecting RET-driven MTC, a role has been hypothesized for RET-G691S non-synonymous polymorphism, though the issue remains controversial. Aim of this study was to define the in vitro contribution of RET-G691S to the oncogenic potential of the RET-S891A, previously shown to harbour low transforming activity.

Methods

The RET-S891A and RET-G691S/S891A mutants were generated by site-directed mutagenesis, transiently transfected in HEK293T cells and stably expressed in NIH3T3 cells. Their oncogenic potential was defined by assessing the migration ability by wound healing assay and the anchorage-independent growth by soft agar assay in NIH3T3 cells stably expressing either the single or the double mutants. Two RET-S891A families were characterised for the presence of RET-G691S.

Results

The functional studies demonstrated that RET-G691S/S891A double mutant displays a higher oncogenic potential than RET-S891A single mutant, assessed by focus formation and migration ability. Moreover, among the 25 RET-S891A carriers, a trend towards an earlier age of diagnosis was found in the MTC patients harboring RET-S891A in association with RET-G691S.

Conclusions

We demonstrate that the RET-G691S non-synonymous polymorphism enhances in vitro the oncogenic activity of RET-S891A. Moreover, an effect on the phenotype was observed in the RET-G691S/S891A patients, thus suggesting that the analysis of this polymorphism could contribute to the decision on the more appropriate clinical and follow-up management.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-015-0231-z) contains supplementary material, which is available to authorized users.

Synchronous occurrence of medullary and papillary carcinoma of the thyroid in a patient with cutaneous melanoma: determination of BRAFV600E in peripheral blood and tissues. Report of a case and review of the literature

The purpose of this study is to describe a case of concurrent medullary and papillary thyroid carcinoma (MTC and PTC) and cutaneous melanoma and to analyze BRAF(V600E) mutation in plasma and tissues. We report the clinical history and the laboratory, imaging, and histopathological findings of a 47-year-old man affected by multinodular goiter. BRAF(V600E)-mutated DNA was quantified in plasma samples and in cancer sections by quantitative real-time polymerase chain reaction (qPCR). At ultrasound examination, the dominant right nodule of the thyroid was weakly hyperechoic and hypervascularized, while the left one was hypoechoic without internal vascularization. Regional lymphadenomegalia was not detected. Basal plasma calcitonin was elevated, and the patient underwent total thyroidectomy and resection of central cervical lymph nodes. Histopathological examination identified two distinct foci of MTC and PTC and micrometastasis of well-differentiated carcinoma in one of the six resected lymph nodes. RET proto-oncogene germline mutations were not detected. Cutaneous melanoma of the thorax was subsequently diagnosed. BRAF(V600E) tissue DNA was detected in PTC and melanoma but not in MTC. The cell-free plasma percentage of BRAF(V600E) DNA was detected in pre-thyroidectomy peripheral blood and was drastically reduced after cancer treatments. This study confirms the occurrence of synchronous MTC and PTC and is the first evidence of the co-existence of melanoma and distinct thyroid cancers of different origin. BRAF(V600E) allele was detected in PTC and melanoma but not in MTC tissues. BRAF(V600E) molecular quantification in pre- and post-treatment blood supports our previous data, suggesting its possible role in diagnosis and follow-up of BRAF-positive tumors.

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.

Simultaneous medullary and differentiated thyroid cancer: a population-level analysis of an increasingly common entity

BACKGROUND

Simultaneous medullary thyroid carcinoma (MTC) and differentiated thyroid carcinoma (DTC) is a rare entity. This is the first population-level analysis of the characteristics and outcomes of simultaneous MTC/DTC.

METHODS

In the Surveillance, Epidemiology, and End Results (SEER) database (1988-2008), patients with simultaneous MTC/DTC were retrospectively compared with those with MTC alone using χ(2), ANOVA, log-rank tests, Cox multivariate regression, and Kaplan-Meier analyses.

RESULTS

A total of 162 patients had simultaneous MTC/DTC; 1,699 had MTC alone. MTC was diagnosed first in 67.9 % of simultaneous MTC/DTC cases. Simultaneous MTC/DTC increased from 2.7 % of all MTCs in 1988-1997 to 12.3 % in 2003-2008. Compared with MTC alone, simultaneous MTC/DTC had smaller mean MTC tumor size (2.9 vs. 2.2 cm; p = 0.005) and lower rates of MTC extrathyroidal extension (25.4 vs. 16.8 %; p = 0.015) and distant metastases (15.7 vs. 9.3 %; p = 0.032). Patients diagnosed with DTC first had smaller mean MTC tumor sizes (p = 0.01), whereas patients diagnosed with MTC first had tumor sizes similar to those of MTC alone. Compared with MTC alone, patients with simultaneous MTC/DTC were more likely to receive thyroidectomy (84.7 vs. 93.2 %; p = 0.003) and radioisotopes (4.4 vs. 25 %; p < 0.001). On Kaplan-Meier analysis, disease-specific survival rates were higher for simultaneous MTC/DTC than for MTC alone (10-year survival rates 87 vs. 81 %; p = 0.056).

CONCLUSIONS

Simultaneous MTC/DTC is diagnosed earlier in tumor development than MTC alone, with a trend toward better prognosis. This entity likely represents a primary tumor with an incidental pathologic finding of a second malignancy. Each malignancy should be treated according to its respective stage and current guidelines.

Medullary and papillary carcinoma of the thyroid gland occurring as a collision tumor with lymph node metastasis: A case report

Introduction

Papillary thyroid carcinoma and medullary thyroid carcinoma are two different thyroid neoplasia. The simultaneous occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma as a collison tumor with metastases from both lesions in the regional lymph nodes is a rare phenomenon.

Case presentation

A 32-year-old Iranian man presented with a fixed anterior neck mass. Ultrasonography revealed two separate thyroid nodules as well as a suspicious neck mass that appeared to be a metastatic lesion. The results of thyroid function tests were normal, but the preoperative calcitonin serum value was elevated. Our patient underwent a total thyroidectomy with neck exploration. Two separate and ill-defined solid lesions grossly in the right lobe were noticed. Histological and immunohistochemical studies of these lesions suggested the presence of medullary thyroid carcinoma and papillary thyroid carcinoma. The lymph nodes isolated from a neck dissection specimen showed metastases from both lesions.

Conclusions

The concomitant occurrence of papillary thyroid carcinoma and medullary thyroid carcinoma and the exact diagnosis of this uncommon event are important. The treatment strategy should be reconsidered in such cases, and genetic screening to exclude multiple endocrine neoplasia 2 syndromes should be performed. For papillary thyroid carcinoma, radioiodine therapy and thyroid-stimulating hormone suppressive therapy are performed. However, the treatment of medullary thyroid carcinoma is mostly radical surgery with no effective adjuvant therapy.

Four novel RET germline variants in exons 8 and 11 display an oncogenic potential in vitro

CONTEXT

Most germline-activating mutations of the RET proto-oncogene associated with inherited medullary thyroid cancer (MTC) are localized in exons 10, 11 and 13-15. Four novel RET variants, located in the extracellular domain (p.A510V, p.E511K and p.C531R) coded by exon 8 and in the intracellular juxtamembrane region (p.K666N) coded by exon 11, were identified on the leukocyte DNA from apparently sporadic cases.

METHODS

Plasmids carrying Ret9-wild-type (Ret9-WT), Ret9-C634R and all Ret9 variants were transfected, and the phosphorylation levels of RET and ERK were evaluated by western blot analyses. The transforming potentials were assessed by the focus formation assay.

RESULTS

The p.A510V, p.E511K and p.C531R variants were found to generate RET and ERK phosphorylation levels and to have a transforming activity higher than that of Ret9-WT variant, but lower than that of Ret9-C634R variant. Differently, the p.K666N variant, located immediately downstream of the transmembrane domain, and involving a conserved residue, displayed high kinase and transforming activities. Computational analysis predicted non-conservative alterations in the mutant proteins consistent with putative modifications of the receptor conformation.

CONCLUSIONS

The molecular analyses revealed an oncogenic potential for all the novel germline RET variants. Therefore, the prevalence of exon 8 genomic variations with an oncogenic potential may be higher than previously thought, and the analysis of this exon should be considered after the exclusion of mutations in the classical hotspots. In addition, on the basis of these functional data, it is advisable to extend the genetic screening to all the first-degree relatives of the MTC patients, and to perform a strict follow-up of familial carriers.

Concurrent occurrence of medullary thyroid carcinoma and papillary thyroid carcinoma in the same thyroid should be considered as coincidental

OBJECTIVES

The simultaneous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) in the same thyroid gland is documented. In this study, we evaluated the prevalence and characteristics of patients with concurrent MTC and PTC. Design Retrospective analysis of patients with MTC in a single centre and review of the literature.

PATIENTS AND MEASUREMENTS

Patients with MTC who underwent initial surgical treatment between 1996 and 2006 at Asan Medical Centre, Seoul, Korea were enrolled. We additionally reviewed the medical records of patients who initially underwent surgery for Graves' disease (GD) or follicular thyroid carcinoma (FTC) during the same period. The concurrent occurrence rate of PTC in MTC patients was compared with that in GD and FTC patients.

RESULTS

Ten of 53 (19%) MTC patients displayed the concomitant PTC. In all 10 cases, the MTC and PTC components were separated by normal thyroid tissue, with the maximal diameters of PTC being less than 1.0 cm in the majority of patients. The rates of concurrent PTC in patients with MTC, GD and FTC were 19%, 15% and 19%, respectively, which were not significantly different.

CONCLUSIONS

Our results suggest that the occurrence of concurrent MTC/PTC is generally a simple reflection of incidental papillary microcarcinoma.

RET genotypes in sporadic medullary thyroid cancer: studies in a large Italian series

BACKGROUND

Highly discrepant data about the different distribution of RET germline single nucleotide polymorphisms (SNPs) among patients with sporadic medullary thyroid cancer (sMTC) and controls are available.

DESIGN AND PATIENTS

In the present case-control study, a wide panel of seven RET SNPs has been tested in the largest sMTC series and in a matched control group.

RESULTS

None of the investigated polymorphisms show a significantly different distribution in patients with sMTC when compared to controls. Twenty haplotypes and 57 genotypes were generated, and their association with the disease and with the clinical features were statistically evaluated. Interestingly, 14 genotypes were found to be unique to sMTC patients and 25 to controls. Two haplotypes and three genotypes, all including the intronic variants IVS1-126 and IVS14-24, were significantly associated with sMTC patients and with a higher tumour aggression. The functional activity of the only nonsynonymous RET variant (c.2071C > A, G691S) was tested for the first time. Interestingly, Western blot analyses showed that the fraction of Ret9-G691S protein located at the plasma membrane level was overrepresented when compared to Ret9-WT, suggesting facilitated targeting at the cell membrane for this variant. However, no transforming activity was shown in a focus formation assay on cells carrying the Ret9-G691S, against a possible oncogenic role of G691S variant.

CONCLUSIONS

RET genotypes including two intronic RET variants were associated with the risk of developing sMTC and to more aggressive behaviour. Further studies are warranted to elucidate whether these RET genotypes are in linkage disequilibrium with another susceptibility gene or whether these variants could play a role in the genesis of sMTC per se.

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.

Polymerase chain reaction-single strand conformational polymorphism analysis of rearranged during transfection proto-oncogene in Chinese familial hirschsprung’s disease

AIM: To investigate the relationship between mutations of rearranged during transfection (RET) proto-oncogene and Chinese patients with Hirschsprung’s disease (HD), and to elucidate the genetic mechanism of familial HD patient at the molecular level.

METHODS: Genomic DNA was extracted from venous blood of probands and their relatives in two genealogies. Polymerase chain reaction (PCR) products, which were amplified using specific primers (RET, exons 11, 13, 15 and 17), were electrophoresed to analyze the single-strand conformational polymorphism (SSCP) patterns. The positive amplified products were sequenced. Forty-eight sporadic HD patients and 30 normal children were screened for mutations of RET proto-oncogene simultaneously.

RESULTS: Three cases with HD in one family were found to have a G heterozygous insertion at nucleotide 18974 in exon 13 of RET cDNA (18974insG), which resulted in a frameshift mutation. In another family, a heterozygosity for T to G transition at nucleotide 18888 in the same exon which resulted in a synonymous mutation of Leu at codon 745 was detected in the proband and his father. Eight RET mutations were confirmed in 48 sporadic HD patients.

CONCLUSION: Mutations of RET proto-oncogene may play an important role in the pathogenesis of Chinese patients with HD. Detection of mutated RET proto-oncogene carriers may be used for genetic counseling of potential risk for HD in the affected families.

Medullary and papillary tumors are frequently associated in the same thyroid gland without evidence of reciprocal influence in their biologic behavior

Papillary thyroid microcarcinoma (mPTC), is a very frequent incidental finding with a frequency varying from a few percent to 35% at postmortem histopathologic examinations. However, the presence of mPTC in patients undergoing thyroidectomy for multinodular goiter (MNG) and for Graves' disease (GD) has been found to be lower. Patients with medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) association have been published as anecdotal case reports, as well as kindred with familial MTC or multiple endocrine neoplasia (MEN) 2A with some members simultaneously affected by MTC and PTC. We studied the prevalence and the biological behavior of MTC associated with PTC, with particular attention to those cases in which a mPTC was incidentally found. Twenty-seven of 196 (13.8%) MTC cases showed an association with PTC and in particular 21 of 190 (11.05%) with an incidental mPTC. This percentage is higher than that reported in the literature on the association of mPTC with GD (2.8%-4.5%) and MNG (3%). Also the percentage of the more general association of MTC/PTC, not restricted to mPTC, found in our series (13.8%) is higher than that reported in studies that analyzed the prevalence of PTC (any size) in patients treated for MNG (7.5%). A similarly high percentage of MTC/PTC had not been reported before and in particular there are no reports on large series of MTC/PTC. We also analyzed the epidemiologic, clinical, and pathologic features of MTC associated and not associated with PTC without finding any difference. In particular the outcome of the MTC did not appear to be influenced by the presence of the PTC and the specific radioiodine treatments. Moreover, although we cannot completely exclude a shared pathogenic event as the cause of both MTC and PTC, the molecular analysis of RET gene alterations did not show any common mutation.

Thyroid carcinomas involving follicular and parafollicular C cells: seventeen cases with characterization of RET oncogenic activation

Recent studies have focused on the occurrence of concomitant medullary-papillary thyroid carcinomas (MTC-PTC). The aims of this report were to compare the frequency of occult PTC in a population with MTC versus a control population that had undergone thyroidectomies and to check whether differences could be related to particular phenotype or genotype. To achieve these goals, we determined the frequency of occult PTC among patients operated for MTC (n = 82) or undergoing total thyroidectomy mainly for goiter and/or nodules (n = 7313) between 1994-2001. We then examined the clinical, histologic, and genetic characteristics (using a bio-chemical family inquiry and screening for RET germline mutations) of patients with associated PTC-MTC. Results show a significantly higher frequency of occult PTC in MTC (14.7%) than in total thyroidectomy (6.8%; p < 0.01). Seventeen cases of MTC or bilateral C-cell hyperplasia (CCH) and separate occult PTC were identified from 16 different families. Although common RET mutations providing evidence of familial forms of MTC were identified in only 3 of 16 families, clinical and histologic features usually seen in inherited forms of MTC such as young age of occurrence, bilateral CCH or associated case in family were found in 11 of the remaining 14 patients. In conclusion, results suggest that the association of MTC-PTC is not only a coincidence. Surprisingly, 11 of 17 MTC-PTC patients exhibited clinical, histologic, and/or family features usually encountered in familial forms despite the fact that no RET defect were present. This suggests the possible involvement of another gene or uncommon abnormality of RET gene.

Diagnosis and management of medullary thyroid carcinoma

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

Concurrent lymph node metastases of medullary and papillary thyroid carcinoma in a case with RET oncogene germline mutation

We report the case of a 72 yr-old woman who underwent total thyroidectomy and resection of neck lymph nodes because of a firm nodule in the right lobe, which was consistent with medullary thyroid carcinoma (MTC) on cytological examination. Histology showed multifocal bilateral MTC; a 2 mm papillary thyroid carcinoma (PTC) was also detected in the right lobe, next to a focus of MTC; five cervical lymph nodes contained MTC. In one right perithyroidal lymph node, concurrent metastases of MTC and PTC were demonstrated. DNA analysis showed a point mutation in exon 14 at codon 804 of the RET proto-oncogene locus, as frequently found in cases of familial MTC (FMTC). To our knowledge, this case represents the first documented case of concurrent lymph node metastases of MTC and PTC in a patient with RET proto-oncogene germline mutation. We report this unique case, discuss related thyroid malignancies, and suggest possible underlying pathogenetic mechanisms.

RET proto-oncogene mutations affecting codon 790/791: A mild form of multiple endocrine neoplasia type 2A syndrome?

BACKGROUND

In patients with multiple endocrine neoplasia type 2A syndrome, prophylactic thyroidectomy is generally recommended at the age of 5 to 6 years. Whether this recommendation is justified for exon 13 mutations is unknown.

METHODS

We analyzed the clinical data from 40 patients harboring RET codon 790/791 mutations (exon 13) who had been treated in 4 specialized centers.

RESULTS

Mean age was 35.2 +/- 21.6 years (range, 5.1-69.0 years). Thirteen patients were index patients (mean age, 57.7 +/- 11.3 years), 27 patients were screening patients (mean age, 24.4 +/- 16.5 years). In the index group, pT-category was: T0, n = 2; T1, n = 6; T2, n = 2; T3, n = 1; and T4, n = 2. Lymph node metastases were found in 5 patients and distant metastases in 1 patient. Postoperatively, 69% of index patients were biochemically cured. In the screening group, pT-category was: T0, n = 19; T1, n = 7; and T2, n = 1. Lymph node metastases were found in 2 patients. Postoperatively, 93% of screening patients were biochemically cured. The youngest patient with medullary thyroid carcinoma was 13.8 years, the youngest patient with lymph node metastases was 46.4 years.

CONCLUSIONS

Patients with RET codon 790/791 mutations seemed to have a less aggressive clinical course compared with patients with classic multiple endocrine neoplasia type 2A syndrome. Still, index patients had a lower biochemic cure rate in comparison with screening patients. Timely total thyroidectomy including lymph node dissection is warranted.