Single nucleotide polymorphisms act as modifiers and correlate with the development of medullary and simultaneous medullary/papillary thyroid carcinomas in 2 large, non-related families with the RET V804M proto-oncogene mutation

Molecular Basis and Natural History of Medullary Thyroid Cancer: It is (Almost) All in the RET

Medullary thyroid cancer (MTC) is a rare disease, which can be either sporadic (roughly 75% of cases) or genetically determined (multiple endocrine neoplasia type 2, due to REarranged during Transfection RET germline mutations, 25% of cases). Interestingly, RET pathogenic variants (mainly M918T) have also been reported in aggressive forms of sporadic MTC, suggesting the importance of RET signalling pathways in the pathogenesis of MTC. The initial theory of RET codon-related MTC aggressiveness has been recently questioned by studies suggesting that this would only define the age at disease onset rather than the aggressiveness of MTC. Other factors might however impact the natural history of the disease, such as RET polymorphisms, epigenetic factors, environmental factors, MET (mesenchymal-epithelial transition) alterations, or even other genetic alterations such as RAS family (HRAS, KRAS, NRAS) genetic alterations. This review will detail the molecular bases of MTC, focusing on RET pathways, and the potential mechanisms that explain the phenotypic intra- and interfamilial heterogeneity.

Multiple endocrine neoplasia type 2: A reveiw

Multiple endocrine neoplasias are rare hereditary syndromes some of them with malignant potential. Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant hereditary cancer syndrome due to germline variants in the REarranged during Transfection (RET) proto-oncogene. There are two distinct clinical entities: MEN 2A and MEN 2B. MEN 2A is associated with medullary thyroid carcinoma (MTC), phaeochromocytoma, primary hyperparathyroidism, cutaneous lichen amyloidosis and Hirschprung's disease and MEN 2B with MTC, phaeochromocytoma, ganglioneuromatosis of the aerodigestive tract, musculoskeletal and ophthalmologic abnormalities. Germline RET variants causing MEN 2 result in gain-of-function; since the discovery of the genetic variants a thorough search for genotype-phenotype associations began in order to understand the high variability both between families and within family members. These studies have successfully led to improved risk classification of prognosis in relation to the genotype, thus improving the management of the patients by thorough genetic counseling. The present review summarizes the recent developments in the knowledge of these hereditary syndromes as well as the impact on clinical management, including genetic counseling, of both individual patients and families. It furthermore points to future directions of research for better clarification of timing of treatments of the various manifestations of the syndromes in order to improve survival and morbidity in these patients.

The synergy of germline C634Y and V292M RET mutations in a northern Chinese family with multiple endocrine neoplasia type 2A

Genetic analysis for germline mutations of RET proto-oncogene has provided a basis for individual management of medullary thyroid carcinoma (MTC) and pheochromocytoma. Most of compound mutations have more aggressive phenotypes than single point mutations, but the compound C634Y/V292M variant in MTC has never been reported. Thus, we retrospectively investigated synergistic effect of C634Y and V292M RET germline mutations in family members with multiple endocrine neoplasia type 2A. Nine of 14 family members in a northern Chinese family underwent RET mutation screening using next-generation sequencing and PCR followed by direct bidirectional DNA sequencing. Clinical features of nine individuals were retrospectively carefully reviewed. In vitro, the scratch-wound assay was used to investigate the difference between the cells carrying different mutations. We find no patients died of MTC. All 3 carriers of the V292M variant were asymptomatic and did not have biochemical or structural evidence of disease (age: 82, 62 and 58). Among 4 C634Y mutation carriers, 2 patients had elevated calcitonin with the highest (156 pg/mL) in an 87-year-old male. Two carriers of compound C634Y/V292M trans variant had bilateral MTC with pheochromocytoma or lymph node metastasis (age: 54 and 41 years, respectively). Further, the compound C634Y/V292M variant had a faster migration rate than either single point mutation in vitro (P < .05). In conclusion, the V292M RET variant could be classified as 'likely benign' according to ACMG (2015). The compound variant V292M/C634Y was associated with both more aggressive clinical phenotype and faster cell growth in vitro than was either single mutation.

Epidemiology of Simultaneous Medullary and Papillary Thyroid Carcinomas (MTC/PTC): An Italian Multicenter Study

Background: The concomitant presence of papillary thyroid cancer (PTC) and medullary TC (MTC) is rare. In this multicentric study, we documented the epidemiological characteristics, disease conditions and clinical outcome of patients with simultaneous MTC/PTC. Methods: We collected data of patients with concomitant MTC/PTC at 14 Italian referral centers. Results: In total, 183 patients were enrolled. Diagnosis was mostly based on cytological examination (n = 58, 32%). At diagnosis, in the majority of cases, both PTC (n = 142, 78%) and MTC (n = 100, 54%) were at stage I. However, more cases of stage II–IV were reported with MTC (stage IV: n = 27, 15%) compared with PTC (n = 9, 5%). Information on survival was available for 165 patients: 109 patients (66%) were disease-free for both PTC and MTC at the last follow-up. Six patients died from MTC. Median time to progression was 123 months (95% confidence interval (CI): 89.3–156.7 months). Overall, 45% of patients were disease-free after >10 years from diagnosis (125 months); this figure was 72.5% for PTC and 51.1% for MTC. Conclusions: When MTC and PTC are concurrent, the priority should be given to the management of MTC since this entity appears associated with the most severe impact on prognosis.

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.

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.

Diversity of mutations in the RET proto-oncogene and its oncogenic mechanism in medullary thyroid cancer

Thyroid cancer is the most common endocrine malignancy and accounts for nearly 1% of all of human cancer. Thyroid cancer has four main histological types: papillary, follicular, medullary, and anaplastic. Papillary, follicular, and anaplastic thyroid carcinomas are derived from follicular thyroid cells, whereas medullary thyroid carcinoma (MTC) originates from the neural crest parafollicular cells or C-cells of the thyroid gland. MTC represents a neuroendocrine tumor and differs considerably from differentiated thyroid carcinoma. MTC is one of the aggressive types of thyroid cancer, which represents 3-10% of all thyroid cancers. It occurs in hereditary (25%) and sporadic (75%) forms. The hereditary form of MTC has an autosomal dominant mode of inheritance. According to the present classification, hereditary MTC is classified as a multiple endocrine neoplasi type 2 A & B (MEN2A & MEN2B) and familial MTC (FMTC). The RET proto-oncogene is located on chromosome 10q11.21. It is composed of 21 exons and encodes a transmembrane receptor tyrosine kinase. RET regulates a complex network of signal transduction pathways during development, survival, proliferation, differentiation, and migration of the enteric nervous system progenitor cells. Gain of function mutations in RET have been well demonstrated in MTC development. Variants of MTC result from different RET mutations, and they have a good genotype-phenotype correlation. Various MTC related mutations have been reported in different exons of the RET gene. We proposed that RET genetic mutations may be different in distinct populations. Therefore, the aim of this study was to find a geographical pattern of RET mutations in different populations.

Papillary thyroid carcinoma and multiple endocrine neoplasia type 2

INTRODUCTION

Papillary thyroid carcinoma (PTC) is exceptional in MEN 2.

RESULTS

The analysis in 135 patients revealed two PTC, without C-cell pathology; both being positive for V804M mutation (RET proto-oncogene).

CONCLUSIONS

Few data are available about PTC in MEN 2, and without C-cell pathology is even less common. More studies are needed to correlate genetics and histology, and even for assessing PTC as only manifestation of MEN 2.

Characterization of V804M-mutated RET proto-oncogene associated with familial medullary thyroid cancer, report of the largest Turkish family

PURPOSE

Analysis of the RET proto-oncogen is very important for diagnosis and prognosis of medullary thyroid cancer (MTC). Genotype-phenotype correlation is also well known. Here we report features of the largest known family in Turkey with the V804M-mutated RET proto-oncogene.

METHODS

Thirty members from three generations were evaluated. A RET proto-oncogen mutation, calcitonin (Ct) measurement and thyroid ultrasound were performed on all individuals. Seventeen members had V804M mutation. Fourteen of these patients underwent total thyroidectomy and additional central lymph node dissection for five subjects.

RESULTS

The mean age of patients with MTC was 46.5 (30-61) years. The mean calcitonin level of RET positive members was 13.27 pg/mL (1-49.8 pg/mL). Three had a basal Ct level above normal limits. Seven of the 14 patients were diagnosed with MTC, and two were diagnosed with papillary thyroid cancer without MTC. One patient had central neck metastasis. Hyperparathyroidism or pheochromocytoma was not detected in any case. Patients who were RET negative, had normal Ct levels and no suspected nodule on ultrasound examination.

CONCLUSIONS

Our study revealed a relatively good prognosis in patients with V804M mutation. Despite the surgery was performed in older age no advance disease was observed.

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.

Testing new susceptibility genes in the cohort of apparently sporadic phaeochromocytoma/paraganglioma patients with clinical characteristics of hereditary syndromes

BACKGROUND

Phaeochromocytoma (PCC) and paraganglioma (PGL) can occur sporadically or as a part of familial cancer syndromes. Red flags of hereditary syndromes are young age and multifocal tumours. We hypothesized that such patients are candidates for further molecular diagnosis in case of normal results in 'classical' genes.

MATERIAL AND METHODS

We selected patients with PCC/PGL under the age of 40 and/or with multiple tumours. First, we tested the genes RET, VHL, NF1, SDHB, SDHC and SDHD. Patients without mutations in these genes were tested for mutations in MAX, TMEM127 and SDHAF2.

RESULTS

In 153 patients included, mutations were detected in the classical genes in 72 patients (47%) [RET-22 (14%), VHL-13 (9%), NF1-3 (2%), SDHB-13 (9%), SDHC-3 (2%), SDHD-16 (11%), SDHB large deletions- 2 (1%)]. One patient with MAXc.223C>T (p.R75X) mutation was detected. It was a male with bilateral, metachronous phaeochromocytomas diagnosed in 36 and 40 years of age. Remarkably, he showed in the period before the MAX gene was detected, a RET p. Y791F variant. During 10-year follow-up, we did not find any thyroid abnormalities. LOH examination of tumour tissue showed somatic loss of the wild-type allele of MAX.

CONCLUSION

Analysis of the MAX gene should be performed in selected patients, especially those with bilateral adrenal phaeochromocytoma in whom mutations of the classical genes are absent. Our study provides with further support that Y791F RET is a polymorphism.

Metachronous appearance of second malignancies in medullary thyroid carcinoma (MTC) patients: a diagnostic challenge and brief review of the literature

Medullary thyroid carcinoma (MTC) is a rare tumour which frequently occurs in the context of the multiple endocrine neoplasia syndromes, where it coexists with other usually benign tumours. The clinical picture varies and distant metastases are frequently present at diagnosis. Calcitonin levels are elevated in the presence of metastatic disease. Two MTC cases are presented, which had elevated postoperative calcitonin levels. Imaging revealed lung lesions which were originally attributed to metastatic disease from the MTC. However, at follow-up, these cases presented unusual features. The rapid increase in the lung lesions and the development of hypercalcaemia in the first patient suggested a second unrelated tumour. Biopsy of the lung lesion was compatible with lung adenocarcinoma. In the second patient, the appearance of a liver mass, although calcitonin levels remained stable, led to biopsy of the lesion: this was negative for calcitonin and compatible with metastatic lung adenocarcinoma. These MTC cases show that further malignancies may coexist with MTC and may obscure the clinical picture and influence the therapeutic decisions, especially in the case of metastatic disease. Features such as unusual imaging characteristics and the development of hypercalcemia, never encountered in MTC outside the MEN2 syndromes, as well as 'disproportionately' low calcitonin levels, incompatible with extensive metastatic disease, were the factors that led to further work-up. Both the cases subsequently proved to carry an unsuspected second malignancy. It is crucial to discriminate the metastatic lesion attributed to MTC from another coexisting primary malignancy, because different therapeutic strategies are needed for each setting.

Familial multinodular goiter syndrome with papillary thyroid carcinomas: mutational analysis of the associated genes in 5 cases from 1 Chinese family

BACKGROUND

Familial papillary thyroid cancer (fPTC) is recognized as a distinct entity only recently and no fPTC predisposing genes have been identified. Several potential regions and susceptibility loci for sporadic PTC have been reported. We aimed to evaluate the role of the reported susceptibility loci and potential risk genomic region in a Chinese familial multinodular goiter (fMNG) with PTC family.

METHODS

We sequenced the related risk genomic regions and analyzed the known PTC susceptibility loci in the Chinese family members who consented to join the study. These loci included (1) the point mutations of the BRAF and RET; (2) the possible susceptibility loci to sporadic PTC; and (3) the suggested potential fMNG syndrome with PTC risk region.

RESULTS

The members showed no mutations in the common susceptible BRAF and RET genomic region, although contained several different heterozygous alleles in the RET introns. All the members were homozygous for PTC risk alleles of rs966423 (C) at chromosome 2q35, rs2910164 (C) at chromosome 5q24 and rs2439302 (G) at chromosome 8p12; while carried no risk allele of rs4733616 (T) at chromosome 8q24, rs965513 (A) or rs1867277 (A) at chromosome 9q22 which were associated with radiation-related PTC. The frequency of the risk allele of rs944289 (T) but not that of rs116909374 (T) at chromosome 14q13 was increased in the MNG or PTC family members.

CONCLUSIONS

Our work provided additional evidence to the genetic predisposition to a Chinese familial form of MNG with PTC. The family members carried quite a few risk alleles found in sporadic PTC; particularly, homozygous rs944289 (T) at chromosome 14q13 which was previously shown to be linked to a form of fMNG with PTC. Moreover, the genetic determinants of radiation-related PTC were not presented in this family.

Association of Toll-like receptor 2 polymorphisms with papillary thyroid cancer and clinicopathologic features in a Korean population

Toll-like receptors (TLRs) single nucleotide polymorphisms (SNPs) were analyzed in patients with papillary thyroid cancer (PTC; n = 133) and their clinicopathologic features and age-matched controls (n = 321) using direct sequencing. PTC patients were divided into subgroups according to size, number, location, extrathyroidal invasion and lymph node metastasis. The two SNPs of TLR2 gene were not associated with the development of PTC. In clinical analysis, two SNPs were associated with location of cancer (rs3804099, P = 0.032, OR, 0.52; 95% CI, 0.28-0.96 in log-additive model; rs3804100, P = 0.039, OR, 0.46, 95% CI, 0.22-0.96 in codominant1 model; P = 0.018, OR, 0.42, 95% CI, 0.21-0.87 in dominant model; P = 0.011, OR, 0.46, 95% CI, 0.25-0.85 in log-additive model). The allele frequencies of two SNPs also showed significant associations with location of cancer (rs3804099, P = 0.046, OR, 0.57, 95% CI, 0.33-0.99 and rs3804100, P = 0.019, OR = 0.52, 95% CI = 0.30-0.90). However, two SNPs were not associated with the clinicopathologic features of PTC. It is suggested that TLR2 polymorphisms may contribute to the clinicopathologic features of PTC, especially the PTC in both lobes.

Genetic alterations in medullary thyroid cancer: diagnostic and prognostic markers

Medullary thyroid carcinoma (MTC) is a rare calcitonin producing neuroendocrine tumour that originates from the parafollicular C-cells of the thyroid gland. The RET proto-oncogene encodes the RET receptor tyrosine kinase, with consequently essential roles in cell survival, differentiation and proliferation. Somatic or germline mutations of the RET gene play an important role in this neoplasm in development of sporadic and familial forms, respectively. Genetic diagnosis has an important role in differentiating sporadic from familiar MTC. Furthermore, depending on the location of the mutation, patients can be classified into risk classes. Therefore, genetic screening of the RET gene plays a critical role not only in diagnosis but also in assessing the prognosis and course of MTC.

Association studies in thyroid cancer susceptibility: are we on the right track?

It is widely accepted that thyroid cancer is strongly determined by the individual genetic background. In this regard, it is expected that sporadic thyroid cancer is the result of multiple low- to moderate-penetrance genes interacting with each other and with the environment, thus modulating individual susceptibility. In the last years, an important number of association studies on thyroid cancer have been published, trying to determine this genetic contribution. The aim of this review is to provide a comprehensive and critical evaluation of the associations reported so far in thyroid cancer susceptibility in case-control studies performed in both non-medullary (papillary and follicular) and medullary thyroid cancers, including their potential strengths and pitfalls. We summarize the genetic variants reported to date, and stress the importance of validating the results in independent series and assessing the functional role of the associated loci.