Mutation analysis of the RET proto-oncogene in Dutch families with MEN 2A, MEN 2B and FMTC: two novel mutations and one de novo mutation for MEN 2A

Hereditary C-cell carcinoma is encountered in multiple endocrine neoplasia type 2A (MEN 2A), MEN 2B, and familial medullary thyroid carcinoma (FMTC). Mutations of the RET proto-oncogene are associated with all three diseases. To obtain an insight into the molecular heterogeneity of MEN 2 syndromes and FMTC in the Netherlands, probands of 20 MEN 2A families, two FMTC families, and seven MEN 2B families were analyzed by the polymerase chain reaction (PCR), DNA sequencing, and restriction enzyme digestion for abnormalities in the RET proto-oncogene. RET mutations were found in all cases. All MEN 2A families had a mutation involving one of five cysteine codons in exons 10 and 11 of RET. Two novel dinucleotide mutations and a de novo mutation were found. Both FMTC families had a mutation of the Cys at codon 618. All MEN 2B probands carried a Met to Thr mutation in exon 16. All mutations could be confirmed by restriction enzyme digestion of PCR amplicons. Identification of the RET mutation in the Dutch population with hereditary C-cell carcinoma facilitates genetic testing for families or individuals at risk for MEN 2A, FMTC, and MEN 2B.     

Predictive Value of Calcium Test for Preoperative Diagnosis of Medullary Thyroid Carcinoma in Patients With Moderately Elevated Basal Calcitonin

ObjectiveMedullary thyroid carcinoma (MTC) can be very aggressive, and early diagnosis is based on routine measurement of serum calcitonin (CT) and RET genetic testing for hereditary forms. Basal serum CT (bCT) concentrations are useful in the early detection of MTC, although it is still unclear whether they can also be used for the differential diagnosis between MTC and C-cell hyperplasia (CCH). Since false-positive results can be obtained with the basal measurement of CT, a provocative test to evaluate stimulated CT (sCT) is often needed. The objective of this study was to investigate the utility of a calcium gluconate test for CT in distinguishing MTC from CCH, a precancerous condition in hereditary forms of MTCs but with unclear significance in sporadic MTCs.MethodsA total of 74 patients underwent the calcium loading test before thyroidectomy, and bCT and sCT levels were compared with histologic results by receiver operating characteristic plot analyses.ResultsA peak CT level of 388.4 pg/mL after stimulation with calcium gluconate was able to significantly distinguish patients with MTC from those with CCH and those without C-cell pathology, with 81.8% sensitivity and 36.5% specificity. A bCT level of 16.1 pg/mL was able to distinguish between these 2 groups of patients with a sensitivity of 90%.ConclusionHigh-dose calcium test is an effective procedure that can be applied for differential diagnosis of MTC and CCH. Reference ranges for calcium sCT levels and CT thresholds in different groups of patients have been identified.     

BRAF initiating mutations in the papillary thyroid carcinoma

Among genetic alterations most important for the initiation of papillary thyroid carcinoma (PTC) is mutation T1799A in the BRAF gene which is the most frequent event (54.5%) in this type of thyroid cancer. It is seen in all stages, from microcarcinoma through clinically overt disease to anaplastic cancer. It has been shown that BRAF mutation is correlated with PTC histotype. It is identified most frequently in classical PTC and in tall cell variant. Moreover, BRAF mutation is described more often in older patients, whereas in young patients RET/PTC rearrangements dominate. In PTC cases with BRAF mutation V600E the prognosis is poorer, with more cancer invasiveness, metastasis and recurrence. The presence of BRAF mutation is related to the specific gene expression signature, different than in cancer cases showing RET/PTC rearrangement or no known initiating mutation.     

Thyroid C-cell hyperplasia in an adolescent with neurofibromatosis type 1

BACKGROUND: Subjects with neurofibromatosis type 1 (NF1) show an increased risk of endocrine tumors, especially pheochromocytoma, whereas thyroid C-cell hyperplasia (CCH) and medullary thyroid carcinoma (MTC) are very rare events described only in adult patients. METHOD: A case of CCH diagnosed in a 14-year-old girl affected with NF1 is reported. Calcitonin serum level after pentagastin was elevated (286 pg/ml). Genetic testing was performed in order to rule out mutations in the RET proto-oncogene. RESULT: No germline mutation previously reported in MEN2 was detected. Multifocal and bilateral CCH was demonstrated by immunohistochemistry. CONCLUSION: It is suggested that in such a genetic background of high risk for malignancy, CCH could be considered as an extremely rare condition likely preceding MTC.     

New insights in the genetics of adrenocortical tumors, pheochromocytomas and paragangliomas.

Recent advances in the molecular genetic of adrenal tumors give new insights in the pathophysiology of these neoplasms in both hereditary and sporadic cases. The practice of genetic counselling in patients with adrenal tumors have been recently changed by the identification and the understanding of new specific hereditary cancer susceptibility syndromes. In the case of sporadic adrenocortical tumors these progress also offer new prognosis predictors.The genetic predisposition to adrenocortical cancer in children has been well established in the Li-Fraumeni and Beckewith-Wiedeman syndromes due to germline p53 mutation located at 17p13 and dysregulation of the imprinted IGF-2 locus at 11p15, respectively. Adrenocortical tumors are also observed in Multiple Endocrine Neoplasia type I syndrome. Cushing's syndrome due to primary pigmented nodular adrenocortical disease have been observed in patients with germline PRKAR1A inactivating mutations. Interestingly allelic loss at 17p13 and 11p15 have been observed in sporadic adrenocortical cancer and somatic PRKAR1A mutations in secreting adrenocortical adenomas. The potential interest of these finding for the diagnosis of these tumors will be discussed. In the case of pheochromocytoma and paraganglioma, the demonstration that three genes encoding three succinate dehydrogenase subunits (SDHD, SDHB, SDHC), belonging to the complex II of the respiratory chain in the mitochondria, are involved in the genetics of familial and especially in apparently sporadic phaeochromocytomas have dramatically modified our practice. Up to date, four diagnosis of familal disease (multiple endocrine neoplasia type II, von Hippel Lindau disease, neurofibromatosis type 1 and hereditary paraganglioma) should be discussed and causative mutations in six different phaechomocytoma susceptibility genes (RET, VHL, NF1, SDHB, SDHD, SDHC) could be identified. In this review, we will perform an update compiling these new clinical, genetic and functional data recently published. We will suggest guidelines for the practice of the phaeochomocytoma genetic testing in the patients and their families, and for an early detection of tumors in the patients or in individuals determined to be at-risk of disease by the presymptomatic genetic testing.     

Demografía,características clínicas y genéticas de pacientes con carcinoma medular de tiroides en los últimos 16 años en Castilla-La Mancha

ObjectiveMedullary thyroid cancer is a rare tumor that is more aggressive and has a worse prognosis than differentiated thyroid cancer. The purpose of this study was to report the demographic, clinical, and genetic characteristics of patients seen in the health care system of the community of Castilla-La Mancha over a 16-year period.Patients and methodsData were collected through a review of patients’ medical records.ResultsThe medical records of 58 patients (mean age at diagnosis, 51 years; range, 6-82 years; 63.8% women) were reviewed. Prevalence rate was 2.84 cases per 100,000 inhabitants, with a high variability between areas (range, 0-5.4 cases per 100,000 inhabitants). Familial cases accounted for 34.5% of all medullary thyroid cancers, and the most common mutation was C634Y. The condition was most commonly diagnosed following palpation of a cervical lump (70.6%). At diagnosis, 56 of 58 patients underwent ultrasound and 8 of 58 patients were tested for serum calcitonin. Tumor multicentricity was reported in 59 and 50% of patients with multiple endocrine neoplasia syndrome type 2A and 2B, respectively, and in no sporadic cases. Fifty-two percent of patients had an advanced stage (iii or iv) at diagnosis. Median follow-up was 36 months (interquartile range, 14-210); 11 patients were lost to follow-up.ConclusionsIn Castilla-La Mancha, medullary thyroid cancer is diagnosed by cervical ultrasound, rather than calcitonin assay. There is a high prevalence of both familial and sporadic medullary thyroid cancer, and a significant variability in the type of proto-oncogen rearranged during transfection mutation as compared to the rest of the Spanish population.     

Polyclonal origin of medullary carcinoma of the thyroid in multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is a dominantly inherited cancer syndrome characterized by medullary thyroid carcinoma (MTC) and other tumors. Since MTC can also occur in a sporadic form and as familial medullary thyroid carcinoma, this neoplasm offers a unique opportunity to investigate the difference of origin, if any, between the sporadic and the hereditary forms of a tumor. While sporadic malignancies have usually been found to result from a mutational event occurring at the single-cell level and are therefore monoclonal, studies on hereditary neoplasms have been scarce and often produced conflicting results. In order to determine the clonal origin of sporadic MTCs and of those occurring in MEN 2 syndromes we used a clonality assay based on a polymorphic trinucleotide repeat of the X-linked human androgen-receptor gene. We found that 10 out of 11 MTCs expressed a polyclonal pattern of X inactivation, including a significant percentage of the cases clinically defined as sporadic. Received: 21 May 1996 / Revised: 14 August 1996     

A gene predisposing to familial thyroid tumors with cell oxyphilia maps to chromosome 19p13.2.

Familial nonmedullary thyroid cancer (FNMTC) is a clinical entity characterized by a phenotype more aggressive than that of its sporadic counterpart. Families with recurrence of nonmedullary thyroid cancer (NMTC) have been repeatedly reported in the literature, and epidemiological data show a very high relative risk for first-degree relatives of probands with thyroid cancer. The transmission of susceptibility to FNMTC is compatible with autosomal dominant inheritance with reduced penetrance, or with complex inheritance. Cases of benign thyroid disease are often found in FNMTC kindreds. We report both the identification of a new entity of FNMTC and the mapping of the responsible gene, named "TCO" (thyroid tumors with cell oxyphilia), in a French pedigree with multiple cases of multinodular goiter and NMTC. TCO was mapped to chromosome 19p13.2 by linkage analysis with a whole-genome panel of microsatellite markers. Interestingly, both the benign and malignant thyroid tumors in this family exhibit some extent of cell oxyphilia, which, until now, had not been described in the FNMTC. These findings suggest that the relatives of patients affected with sporadic NMTC with cell oxyphilia should be carefully investigated.     

Prevalence of hypergastrinemia in patients with hyper- and hypothyroidism: impact for calcitonin?

OBJECTIVES: To evaluate the prevalence of hypergastrinemia in patients with hyperthyroidism and hypothyroidism and to determine whether gastrin-induced hypercalcitonemia could explain the high prevalence of thyroid C-cell hyperplasia among patients with hyperthyroidism. METHODS: Concentrations of gastrin and of hCT were determined by commercially available radioimmunoassays. RESULTS: Elevated serum concentrations of gastrin were found in 17 of 161 (10.5%) patients with manifest hyperthyroidism (Graves' disease) and in 4 of 37 (10.8%) and 23 of 255 (9.0%) patients with manifest or subclinical hypothyroidism, respectively. Only 2 cases of hypergastrinemia of 255 subclinically hypothyroid patients (0.8%) could not be linked to thyroid autoimmune disease by either biochemical or sonographic criteria. Four patients with Graves' disease presented elevated plasma concentrations of calcitonin, but none of these patients also had an elevated serum gastrin. CONCLUSIONS: The prevalence of hypergastrinemia in autoimmune thyroid disease is about 10%. The determination of gastrin in subclinical hypothyroidism is not cost-effective in the absence of biochemical and/or sonographic markers of autoimmune thyroid disease. The determination of gastrin is of no use to predict the presence of C-cell hyperplasia commonly seen in patients with Graves' disease.     

Correlation between gender and spontaneous C-cell tumors in the thyroid gland of the Wistar rat

In many rat strains, C-cell hyperplasia occurs in an age-dependent manner and is often associated with multifocal C-cell carcinoma. The purpose of this study was to investigate the spectrum of spontaneous, proliferative C-cell disorders by gender in Wistar rats throughout their lifespan. The incidence of C-cell hyperplasia shows a significant increase with age (P<0.001) and is much higher in female rats than in male rats (P<0.05). From 3 to 24 months of life, 27.5% of female rats showed a normal C-cell pattern, 55.0% showed C-cell hyperplasia, and 17.5% showed C-cell tumors; while 57.5% of male rats showed a normal C-cell pattern, 32.5% showed C-cell hyperplasia, and 10% showed C-cell tumors. Although the overall frequency of C-cell neoplasms in females was nearly double that in males, these data are not statistically significant. However, the number of C-cell tumors showed a significant increase with age (P<0.05). Therefore, we can conclude that there were significant differences in the incidence of the total spectrum of C-cell proliferative abnormalities in the thyroid gland of Wistar rats that were both age-dependent and gender-dependent.     

Tumorigenesis in colorectal tumors from patients with hereditary non-polyposis colorectal cancer

Tumorigenesis of colorectal cancer in patients with hereditary non-polyposis colorectal cancer (HNPCC) has been postulated to follow a different pathway from that of sporadic colorectal tumors. A characteristic of HNPCC-associated tumors is the replication error phenotype. We studied tumorigenesis in 8 fresh-frozen and 67 paraffin-embedded colorectal tumors derived from 29 families with HNPCC or a familial aggregation of colorectal cancer. By using intragenic markers, inactivation of the wild-type allele of hMLH1 was shown to occur through loss of heterozygosity and not through a somatic point mutation. Microsatellite instability is very common and occurs early in almost all colorectal tumors from HNPCC patients. Transforming growth factor β type II receptor (TβRII) mutations occur in these tumors at a high frequency. Of colorectal cancers from families with HNPCC, 63% have frameshift mutations in TβRII, compared with 10% of sporadic colorectal cancers. APC and K-RAS mutations appear to be as frequent in the HNPCC tumors as in the sporadic counterpart. Received: 3 March 1997 / Accepted: 23 June 1997     

Contribution of BRCA1 germline mutation in patients with sporadic breast cancer

Hereditary artifacts in BRCA1 gene have a significant contributory role in familial cases of breast cancer. However, its germline mutational penetrance in sporadic breast cancer cases with respect to Pakistani population has not yet been very well defined. This study was designed to assess the contributory role of germline mutations of this gene in sporadic cases of breast cancer. 150 cases of unilateral breast cancer patients, with no prior family history of breast cancer and no other disorders or diseases in general with age range 35–75 yrs, were included in this study.Mutational analysis for hot spots on Exon 2, 3 and 13 of BRCA1 was done by using Single Strand Conformational Polymorphism (SSCP). Sequence analysis revealed five variants (missense) and one novel splice site mutation at exon 13. No germline mutation was observed on the remaining exons with respect sporadic breast cancer cases in Pakistani population. A vast majority of breast cancer cases are sporadic; the present study may be helpful for designing a better genetic screening tool for germline BRCA mutations in sporadic breast cancer patients of Pakistani population. Further studies involving a screening of entire coding region of BRCA1 is required to explore the merits of genetic diagnosis and counseling in breast cancer patients.     

Developmental defects in Gorlin syndrome related to a putative tumor suppressor gene on chromosome 9.

Gorlin syndrome is an autosomal dominant disorder that predisposes to basal cell carcinomas of the skin, ovarian fibromas, and medulloblastomas. Unlike other hereditary disorders associated with cancer, it features widespread developmental defects. To investigate the possibility that the syndrome is caused by mutation in a tumor suppressor gene, we searched for loss of heterozygosity in 16 sporadic basal cell carcinomas, 2 hereditary basal cell carcinomas, and 1 hereditary ovarian fibroma and performed genetic linkage studies in five Gorlin syndrome kindreds. Eleven sporadic basal cell carcinomas and all 3 hereditary tumors had allelic loss of chromosome 9q31, and all informative kindreds showed tight linkage between the Gorlin syndrome gene and a genetic marker in this region. Loss of heterozygosity at this chromosomal location, particularly in hereditary tumors, implies that the gene is homozygously inactivated and normally functions as a tumor suppressor. In contrast, hemizygous germline mutations lead to multiple congenital anomalies.     

Evaluation of DLC1 as a prostate cancer susceptibility gene: mutation screen and association study

A gene or genes on chromosome 8p22-23 have been implicated in prostate carcinogenesis by the observation of frequent deletions of this region in prostate cancer cells. More recently, two genetic linkage studies in hereditary prostate cancer (HPC) families suggest that germline variation in a gene in this region may influence prostate cancer susceptibility as well. DLC1 (deleted in liver cancer), a gene in this interval, has been proposed as a candidate tumor suppressor gene because of its homology (86% similarity) with rat p122 RhoGAP, which catalyzes the conversion of active GTP-bound rho complex to the inactive GDP-bound form, and thus suppresses Ras-mediated oncogenic transformation. A missense mutation and three intronic insertions/deletions in 126 primary colorectal tumors have been previously identified. However, there are no reports of DLC1 mutation screening in prostate tumors or in germ line DNA of prostate cancer patients. In this study, we report the results of the first mutation screen and association study of DLC1 in genomic DNA samples from hereditary and sporadic prostate cancer patients. The PCR products in the 5' UTR, all 14 exons, exon-intron junctions, and 3' UTR were directly sequenced in 159 HPC probands. Eight exonic nucleotide polymorphisms (SNPs) were identified, only one of which resulted in an amino acid change. Twenty-three other SNPs were identified in intronic regions. Seven informative SNPs that spanned the complete DLC1 gene were genotyped in an additional 249 sporadic cases and 222 unaffected controls. No significant difference in the allele and genotype frequencies were observed among HPC probands, sporadic cases, and unaffected controls. These results suggest that DLC1 is unlikely to play an important role in prostate cancer susceptibility.     

The clinical implications of a positive calcitonin test for C-cell hyperplasia in genetically unaffected members of an MEN2A kindred.

C-cell hyperplasia precedes the development of medullary thyroid carcinoma in multiple endocrine neoplasia type 2A (MEN2A). Identification of abnormal calcitonin levels after a provocative stimulus is a technique that has been widely used to diagnose this preneoplastic condition in an early stage during the development of medullary thyroid carcinoma, when total thyroidectomy is likely to be curative. In a MEN2A kindred, we identified seven individuals with abnormal calcitonin test results, whose carrier state was questionable. Five of these people were thyroidectomized, and C-cell hyperplasia was diagnosed. Four of these individuals were the offspring of a mother who is at risk for the development of MEN2A but who has had normal calcitonin test results throughout the years and of a father who is not at risk but who has had abnormal test results over a period of 10 years, without evidence of progressive elevation. None of these people developed other manifestations of MEN2A. DNA analysis using markers linked to the MEN2A gene demonstrated, with > 99% likelihood, that none of the individuals who could be genotyped was a gene carrier. C-cell hyperplasia due to some mechanism other than the presence of the MEN2A gene may also occur in MEN2A kindreds. DNA analysis offers an important additional tool for proper diagnosis in the clinical management of MEN2A families.     

Unusual Case of Multiple Endocrine Neoplasia Type 2A Syndrome Without Medullary Thyroid Carcinoma

ObjectiveTo present an unusual case of multiple endocrine neoplasia type 2A (MEN 2A) syndrome and to describe how this case differs from the typical clinical features and usual genetic variations seen in classic MEN 2A syndrome.MethodsWe describe the work-up, diagnosis, and treatment course of a patient who presented with multifocal pheochromocytomas, parathyroid adenoma, thyroid abnormalities, and a RET mutation.ResultsA 65-year-old man with previously treated pheochromocytoma presented with a parathyroid adenoma, multiple thyroid nodules, and a RET polymorphism. C-cell hyperplasia (CCH) or medullary thyroid carcinoma (MTC) occurs with nearly 100% penetrance in patients with MEN 2A syndrome. Our patient did not have CCH or frank MTC, but he expressed the other manifestations of the MEN 2A syndrome.ConclusionMEN 2A syndrome is characterized by the occurrence of MTC, pheochromocytomas, and parathyroid hyperplasia or adenomas. It is inherited in an autosomal dominant fashion, and more than 80% of patients with MEN 2A have a specific substitution on codon 634 of the RET proto-oncogene. Despite the nearly 100% penetrance of MTC or CCH in patients with MEN 2A, our patient did not have this. Additionally, he exhibited a RET mutation that is uncommonly seen in classic MEN 2A syndrome. Our patient may have a MEN 2A variant or a pseudo-MEN 2A syndrome. (Endocr Pract. 2011;17:e4-e7)     

C-cell hyperplasia, pheochromocytoma and sympathoadrenal malformation in a mouse model of multiple endocrine neoplasia type 2B

Dominantly inherited multiple endocrine neoplasia type 2B (MEN2B) is characterized by tumors of the thyroid C-cells and adrenal chromaffin cells, together with ganglioneuromas of the gastrointestinal tract and other developmental abnormalities. Most cases are caused by substitution of threonine for Met918 in the RET receptor tyrosine kinase, which is believed to convert the RET gene to an oncogene by altering the enzyme's substrate specificity. We report the production of a mouse model of MEN2B by introduction of the corresponding mutation into the ret gene. Mutant mice displayed C-cell hyperplasia and chromaffin cell hyperplasia progressing to pheochromocytoma. Homozygotes did not develop gastrointestinal ganglioneuromas, but displayed ganglioneuromas of the adrenal medulla, enlargement of the associated sympathetic ganglia and a male reproductive defect. Surprisingly, homozygotes did not display any developmental defects attributable to a loss-of-function mutation. Thus, while our results support the conclusion that the Met918Thr substitution is responsible for MEN2B, they suggest that the substrate specificity of the RET kinase does not interfere with its normal role in the development of the kidneys and enteric nervous system.     

Medullary thyroid carcinoma: the comparison of the hereditary and sporadic types of cancer

INTRODUCTION: The assessment of frequency and type of mutation and differences in prognosis between sporadic and hereditary type of medullary thyroid carcinoma (MTC), based on own DNA analysis, was performed. MATERIAL AND METHODS: The group of 190 persons with hereditary MTC or asymptomatic mutation carriers was analyzed. Patients with sporadic MTC without RET gene mutation were included into control group (708 persons). The recognition of MTC type was based on assessment of family history, physical examination and genetic analysis. The family history consisted of information about MTC, pheochromocytoma and other neoplasms and hyperparathyroidism in relatives. RESULTS: The mutations located in codon 634 of exon 11 were the most often (43% of all mutations and 49% of mutations in syndrome MEN 2A/FMTC). The age of diagnosis was ranged between 7 and 71 years (mean age: 39 +/- 15.2 years, median age: 41 years). In hereditary MTC the mean age of diagnosis was 27 +/- 13.9 years and was significantly lower than in sporadic one, where it was 45.7 +/- 14.3 years. The relationship between diagnosis, age and subtypes of hereditary MTC was assessed--no significant differences in examined subgroups were observed. The mean age of diagnosis in MEN 2A/FMTC and MEN 2A syndrome was 28-29 years, in MEN 2B - 21 years. The overall survival in sporadic MTC after 5 years was 97%, in hereditary MTC - 79%. Analysis performed after excluding suprarenal causes of death revealed no statistically significant differences in overall survival between both subtypes of MTC. CONCLUSIONS: 1. Hereditary MTC is still diagnosed too late, besides of DNA analysis. 2. In hereditary and sporadic MTC the prognosis is comparable.     

Papillary renal cell carcinoma: analysis of germline mutations in the MET proto-oncogene in a clinic-based population

Approximately 10% of all renal cell carcinomas (RCCs) present a distinctive papillary histology. Familial papillary RCC (PRCC) has been described, but the majority of cases appear to be sporadic. Recently, germline mutations in the MET proto-oncogene on chromosome 7 have been identified in families with hereditary PRCC. We evaluated 59 patients with PRCC for the frequency of MET germline mutations to determine the value of genetic screening of this patient population. Between 1976 and 1997, 165 patients were identified with PRCC by retrospective chart review. Fifty-nine of 133 surviving patients agreed to provide a family history, a blood specimen, and informed consent for genetic research. DNA was isolated from peripheral blood leukocytes. Denaturing high-performance liquid chromatography (DHPLC) followed by genomic sequencing was performed on eight exons of the MET proto-oncogene, including exons 5-7 of the extracellular domain, exon 14, and exons 16-19 of the tyrosine kinase domain. The 59 patients in this study included 49 men and 10 women with a mean age at diagnosis of 61 years. Bilateral and/or multifocal disease was present in 13 cases (22%). No germline mutations were detected in the studied exons of the MET proto-oncogene (exons previously reported to contain deleterious mutations in familial PRCC). No pathological MET proto-oncogene germline mutations were identified in 59 patients with PRCC. The germline mutation rate in this clinic-based population of individuals with PRCC approaches 0% (CI = 0-6.18). MET proto-oncogene germline mutation screening does not appear to be clinically indicated in patients with PRCC without additional evidence for a genetic predisposition (positive family history, unusual age at onset, bilateral disease).