Clinical screening as compared with DNA analysis in families with multiple endocrine neoplasia type 2A

Psychological risks of genetically testing children for a hereditary cancer syndrome

Parents in families with a hereditary cancer syndrome are often familiar with periodical clinical testing of both themselves and their children. Genetic testing is an additional early diagnostic option that is becoming available for an increasing number of hereditary cancer syndromes. Participants in genetic counseling programs for cancer syndromes are often parents who apply for their children. If a child is identified as a carrier of a specific disease-causing gene mutation, sometimes its parents must decide on when it will be treated can treatment be postponed until expression of the disease or should the child receive presymptomatic surgery? We discuss some of the possible risks of genetically testing children: distress as a result of ambivalent feelings towards testing, preoccupation with disease-related signs, changes in family interactions, the burdening prospect of a future disease and medicalization of the carrier-child.

Advances and controversies in the diagnosis and management of medullary thyroid carcinoma

Recent advances in the diagnosis and treatment of medullary thyroid carcinoma (MTC) have been significant, but some issues remain controversial. MTC may occur either as a hereditary or a nonhereditary entity. Hereditary MTC can occur either alone--familial MTC (FMTC)--or as the thyroid manifestation of multiple endocrine neoplasia type 2 (MEN 2) syndromes (MEN 2A and MEN 2B). These hereditary disorders are due to germline mutations in the RET proto-oncogene. Early diagnosis and treatment considerably improve the prognosis in patients with MTC. Genetic testing can identify almost all affected individuals with hereditary disease and permits early thyroidectomy in gene carriers. Plasma CT is an excellent marker for postoperative follow-up. Imaging studies help delineate recurrent or metastatic lesions. Treatment of recurrent or metastatic disease is primarily surgical, including either palliative or microdissective surgery. Radiation therapy is reserved for skeletal metastasis or nonresectable metastatic MTC. Efficacy of current chemotherapy programs is not well established. Overall, the 10-year survival rates are approximately 65%.

Genetic screening for RET mutations in families with multiple endocrine neoplasia 2 syndromes

Mutations in the RET proto-oncogene have recently been recognized to be responsible for the inherited multiple endocrine neoplasia type 2 syndrome. As expected, Greek patients with MEN2 and FMTC carry RET mutations similar to those of other ethnic groups. In those regions of the gene that were analyzed, mutations were detected in six out of six families with classical MEN2A, three out of five of the families with familial MTC, and one case with MEN2B. Presymptomatic screening using DNA analysis has now replaced calcitonin stimulation tests in the offspring of families where the mutation has been characterized. The use of these methods will improve the prognosis in MEN2 patients and will also reduce the psychological burden of risk for a potentially lethal disease on family members.

Rapid, nonradioactive screening for mutations in exons 10, 11, and 16 of the RET protooncogene associated with inherited medullary thyroid carcinoma

Germline mutations in exons 10, 11, and 16 of the RET protooncogene are associated with the heritable cancer syndromes multiple endocrine neoplasia (MEN) type 2A, familial medullary thyroid carcinoma (FMTC), and MEN type 2B. Nonradioactive mutation analysis with nondenaturing Phastgels® and the Phast System™ was performed on DNA amplified by the polymerase chain reaction from exons 10, 11, and 16 of the RET protooncogene from patients with MEN 2A, MEN 2B, or FMTC. The analysis requires ∼45–90 min for electrophoresis and 35 min for staining. This assay detected 20 of 21 different mutations that represented ∼90% of all known mutations associated with these lesions. A rare silent polymorphism within exon 10 was also detected. This form of mutation analysis provides simple, rapid, and highly sensitive nonradioactive detection of mutations known to be associated with MEN 2A, FMTC, and MEN 2B.

Mutation of RET codon 768 is associated with the FMTC phenotype

Multiple endocrine neoplasia type 2A (MEN 2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC) are inherited cancer syndromes resulting from mutations in the RET proto-oncogene. Missense mutations of five codons in exons 10 and 11 are found in both MEN 2A and FMTC families, while mutations at codon 768 in exon 13 have been identified in three FMTC families. We report here the results of mutation analysis on a large multi-generation family with multiple cases of medullary thyroid carcinoma (MTC) or C-cell hyperplasia and two individuals with isolated adrenal medullary hyperplasia. A mutation in exon 13, which alters codon 768 from a GAG (Glu) to a GAC (Asp), was found to segregate with the FMTC phenotype in this family but not with the adrenal medullary hyperplasia. These findings suggest that the codon 768 mutation does not predispose to adrenal medullary hyperplasia, but is an accurate predictor of the MTC phenotype in this family.

The molecular genetics of multiple endocrine neoplasia type 2A and related syndromes

Identification of RET gene mutations in patients at-risk for the development of the hereditary forms of medullary thyroid carcinoma has simplified management and expanded the scope of indications for surgical intervention. Patients who carry this mutation can be offered thyroidectomy at a very young age, hopefully at a point when the cancer has not yet developed or spread. Those who are found not to have inherited the mutation are spared further genetic and biochemical screening. This achievement marks a new paradigm in surgery--the recommendation that an operation be performed based on the result of a genetic test. Experience with management of patients with multiple endocrine neoplasia types 2A and 2B and with familial, non-multiple endocrine neoplasia medullary thyroid carcinoma will provide information that will aid in the future management of patients with other hereditary cancers.

Expression of the calcitonin gene family in medullary thyroid carcinoma

The regulatory peptide calcitonin was discovered in 1962. During the last decade it has been demonstrated to be part of a gene family. Calcitonin is synthesized in the parafollicular cells (C cells) of the thyroid gland. These cells give rise to an endocrine tumor, medullary thyroid carcinoma (MTC), which is found in a sporadic and an inherited form. Calcitonin is used as a tumor marker for MTC. The calcitonin gene was demonstrated in 1981 to give rise to an alternative peptide product, alpha-CGRP, and a second gene encoding a very similar peptide, beta-CGRP, has also been identified. A third CGRP-like peptide, amylin, was identified in 1986. This article summarizes the present knowledge about gene structure, regulation of gene expression, and expression of the calcitonin gene family in MTC and in MTC-derived cell lines. The methods employed for detection of gene expression and for measurement and characterized of peptide products are described, and finally the relevance of biochemical tumor markers is discussed in relation to the new diagnostic methods for inherited MTC based on molecular biological techniques.

Multiple endocrine neoplasia type II and familial medullary thyroid carcinoma. Impact of genetic screening on management

The identification of ret protooncogene mutations in MEN-II and Hirschsprung disease has not only improved the clinical management of these genetic conditions but has also provided important information regarding mechanisms of transformation and neural crest development. An indication of how neural-crest cells migrate during embryonic life and the key processes involved in their differentiation now seems within reach. The continued pace of scientific discovery suggests that our understanding of and ability to prevent or treat hereditary and sporadic forms of MTC will continue to improve.

Familial medullary thyroid carcinoma: not a distinct entity? Genotype-phenotype correlation in a large family

BACKGROUND

Multiple endocrine neoplasia type 2A (MEN 2A) is a hereditary syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and hyperparathyroidism. Familial MTC (FMTC) is characterized by MTC only. Both MEN 2A and FMTC are caused by germline mutations of the RET proto-oncogene.

PURPOSE

To assess genotype/phenotype correlations, large families have to be examined periodically over a long period using an extensive screening program.

PATIENTS AND METHODS

Since 1973, we screened a large family with hereditary C cell carcinoma for MTC, pheochromocytoma, and parathyroid disease by clinical tests and imaging methods. A germline codon Cys618 to Ser mutation in the RET proto-oncogene was recently identified in this family. The disease phenotype associated with this mutation was compared with that of Cys634 mutations in some other large MEN 2A families.

RESULTS

The distinct course of disease in the family described here is similar to that in other FMTC families and MEN 2A families with a Cys618 mutation of the RET gene, but clearly different from that in families with a Cys634 mutation. The frequency of pheochromocytomas and parathyroid disease is clearly lower, whereas cure rates and life expectancy are higher. However, in families with a Cys618 mutation, pheochromocytoma and parathyroid disease do occur.

CONCLUSION

In FMTC families with cysteine codon mutations of the RET proto-oncogene, screening for other endocrinopathies is mandatory, since these may not be MTC-only families. Therefore, we suggest that MEN 2A families should not be subclassified into MEN 2A and FMTC, but rather according to their specific mutation in the RET protein (i.e., for this family MEN 2A RET C618S).

Early presentation of metastatic medullary carcinoma in multiple endocrine neoplasia, type IIA: implications for therapy

A girl 5 years 11 months of age, belonging to an extensive kindred with multiple endocrine neoplasia, type IIA (MEN IIA), was found to have multifocal medullary thyroid carcinoma with metastasis in one paraglandular lymph node after positive findings on a calcium-pentagastrin stimulation test. Her sister, 3 years 8 months of age, also had an elevated calcitonin level, and thyroidectomy revealed C-cell hyperplasia and a focus of medullary thyroid carcinoma. These two cases underscore the need for prophylactic thyroidectomies in MEN IIA patients as young as 5 years of age and strict yearly provocative screening beginning at age 1 year.

Distinction between sporadic and hereditary medullary thyroid carcinoma (MTC) by mutation analysis of the RET proto-oncogene. "Study Group Multiple Endocrine Neoplasia Austria (SMENA)"

Germline and somatic mutations of the RET proto-oncogene are important pathogenetic factors in hereditary and sporadic forms of medullary thyroid carcinoma (MTC). We have therefore analysed exons 10, 11, 13, 14 and 16 of this gene in 85 individuals from 16 Austrian families who, according to clinical criteria, were at risk of suffering from hereditary forms of MTC. We found mutations (codons 620,634 and 804) in the germline of 3 families with familial medullary thyroid carcinoma (FMTC), of 5 with multiple endocrine neoplasia type 2A (MEN 2A; codon 634) and of 2 with multiple endocrine neoplasia type 2B (MEN 2B; codon 918). The codon 804 mutation in one FMTC family led to the substitution of Val (GTG) for Met (ATG) and has not been reported previously. Within these 10 families, 32 carriers and 32 non-carriers were identified. Somatic mutations in the tumors of 3 other families suggested a sporadic origin of the neoplasms. In the remaining 3 families, no mutations were identified. Fifty-nine individuals with an apparently sporadic MTC lacked germline mutations in the RET gene, whereas 7 of 24 available tumors (29%) contained a somatic mutation in codon 918. Our findings provide further evidence that molecular genetic evaluation of hereditary and sporadic forms of MTC is a necessary prerequisite for counselling and management of patients and their families.

RET mutation screening in familial cutaneous lichen amyloidosis and in skin amyloidosis associated with multiple endocrine neoplasia

In several families, multiple endocrine neoplasia type 2A (MEN 2A) has been found in association with cutaneous lichen amyloidosis. It has been debated, however, whether the skin amyloidosis found in MEN 2A families, localized exclusively in the interscapular area, represents the same anomaly as that found in autosomal dominant familial cutaneous lichen amyloidosis, which is more generalized. We screened two MEN 2A families with associated skin amyloidosis for germline mutations in the RET gene responsible for the MEN 2A cancer syndrome, and found the same mutation characteristic of MEN 2A in both families. We also screened probands from three pedigrees with familial cutaneous lichen amyloidosis for RET mutations. In none of the RET coding and flanking intronic sequences was a mutation detected. This most probably indicates that skin amyloidosis found in some MEN 2A families and familial cutaneous lichen amyloidosis are different conditions. Consequently, patients with apparent familial cutaneous lichen amyloidosis do not appear to be at risk for MEN 2A.

Overexpression of p53 protein and DNA content are important biologic prognostic factors for thyroid cancer

BACKGROUND

Many factors gave been reported to be of prognostic importance for thyroid cancer. Biologic aggressiveness may influence postoperative recurrences and the prognosis of thyroid cancer. Immunohistochemical staining for the p53 protein and DNA content are novel factors that suggest biologic aggressiveness.

METHODS

Retrospective study of the survival rate after operation of differentiated thyroid cancer was undertaken at Osaka Police Hospital. Age, gender operative method, extent of lymph node dissection, use of radioiodine, primary or recurrent tumor, tumor size and invasion, lymph node involvement, presence of distant metastases, DNA ploidy, percentage of S phase and G2M phase fractions, positive staining for the p53 protein, and histologic type and subtype were evaluated as possible prognostic factors by univariate and multivariate analyses of survival.

RESULTS

Positive staining for the p53 protein was related to postoperative local recurrence, and DNA ploidy was related to distant metastatic recurrence. Univariate analysis suggested that age, tumor size and invasion, lymph node involvement, presence of distant metastases, percentage of S phase fraction, histologic subtype, DNA ploidy, and positive staining for the p53 protein were significant prognostic factors. Multivariate analysis suggested that positive staining of the protein and DNA ploidy were independent prognostic factors for overall survival.

CONCLUSIONS

Both positive staining for the p53 protein and DNA ploidy, which suggest biologic aggressiveness, are independent prognostic factors for overall survival of patients with thyroid cancer, Examination of these biologic factors may provide new information regarding postoperative recurrences and the prognosis of thyroid cancer.

Multivariate analysis of patients with medullary thyroid carcinoma. Prognostic significance and impact on treatment of clinical and pathologic variables

BACKGROUND

The prognostic significance of the histologic and clinical features of medullary thyroid cancer (MTC) and their impact on therapy and outcome have been evaluated infrequently in the same series.

METHODS

Fifty-tree patients with MTC (32 females, 21 males; 44 sporadic, 9 familial MTC [4 families]; mean age: 46.11 +/- 14.04 years) who were operated on consecutively between 1970 and 1992 were studied. All pathology slides were reviewed. Patients were followed with clinical examination, serum calcitonin (CT), and carcinoembryonic antigen (CEA) assay, and imaging procedures (median follow-up: 4 years; mean: 5.66 +/- 4.85 years; range: 0-19 years). Impact on survival was evaluated with Kaplan-Meier survival curves compared with the log rank test for these variables: familiarity, sex, age, pT, N, M, stage, histotype, necrosis, calcitonin, gene-related peptide (CGRP), CT, CEA, thyroglobulin, chromogranin A, chromogranin A PHE5, neuron-specific enolase, amyloid, argyrophilia, synaptophysin Y38, external radiotherapy, chemotherapy, 131I therapy, postsurgical serum CT, and postsurgical serum CEA, Multivariate analysis was performed using Cox's proportional hazards model for statistically significant factors (P < 0.05).

RESULTS

Ten- and 15-year cause-specific survival were 71% and 54%. Nineteen patients (35.8%) appeared to be cured and 8 (15.1%) were alive with high serum CT levels but no proven metastases. Eight recurrences as distant sites and four at the cervical region were diagnosed. Stage M, N, necrosis, and postsurgical CT and CGRP were significant prognostic factors for survival by univariate analysis, but only the stage was significant by multivariate analysis.

CONCLUSIONS

Stage and postsurgical serum CT level are the most powerful and the most useful prognostic factors for MTC, while survival did not correlated significantly with the majority of available immunohistochemical markers.

Application of genetic screening information to the management of medullary thyroid carcinoma and multiple endocrine neoplasia type 2

Application of RET proto-oncogene mutation analysis to the clinical management of MEN 2 and FMTC has simplified and enhanced the power of earlier used screening and treatment efforts for hereditary MTC. The approaches outlined herein are cost-effective, have improved diagnostic accuracy, and hold the promise of improved cure rates for this neoplasm. Further studies to elucidate the mechanism by which these activating mutations cause transformation may lead to other strategies for prevention or treatment of this neoplasm.

Physiologic versus neoplastic C-cell hyperplasia of the thyroid: separation of distinct histologic and biologic entities

BACKGROUND

Although hyperplasia of C-cells has been described in association with various pathologic and physiologic conditions, criteria for its diagnosis are poorly defined. Both neoplastic and physiologic C-cell proliferations have been lumped together under the umbrella designation of C-cell hyperplasia (CCH), creating considerable confusion among clinicians and pathologists.

METHODS

in order to compare the morphologic and immunohistochemical characteristics of the two major types of CCH, we examined thyroid sections of 17 patients with familial forms of C-cell hyperplasia and/or neoplasia and tissue sections of 19 thyroid glands known to have reactive or physiologic CCH (at least 50 C-cells per one low power field, 100X). Hematoxylin and eosin (H & E) stained sections and immunohistochemical stains for calcitonin were assessed in each case.

RESULTS

Physiologic or reactive CCH was not recognized with certainty on H & E stains in any of the cases due to morphologic similarities between C-cells and adjacent follicular cells. Detection of this form of hyperplasia, which was predominantly diffuse, required calcitonin immunostains and quantitative analysis. Conversely, nodular and diffuse neoplastic CCH was easily identified with conventional H & E stains at the periphery of 11/12 (92%) familial medullary thyroid carcinomas (MTC). In the other five cases, neoplastic C-cell hyperplasia was the only pathologic finding on thyroidectomy performed for elevated serum calcitonin levels detected via provocative biochemical screening or identification of the mutated RET proto-oncogene by genetic analysis. The C-cells in this neoplastic form of CCH were large, mildly to moderately atypical, and confined within the basement membrane of thyroid follicles. Moreover, these cells were cytologically indistinguishable from those of invasive MTC cells.

CONCLUSIONS

Physiologic and neoplastic CCH are biologically and morphologically distinct entities. The former cannot be recognized with certainty with conventional stains and requires immunohistochemistry and quantitative analysis for diagnosis. The latter consists of mildly to moderately atypical C-cells that can be identified with H & E stained sections. Consequently, the number of C-cells is of no importance for the diagnosis of neoplastic CCH which is considered to be the precursor (medullary carcinoma in situ) of invasive medullary carcinoma.

Medullary thyroid carcinoma in children with multiple endocrine neoplasia types 2A and 2B

Recently it has become possible to identify persons who have multiple endocrine neoplasia (MEN) syndrome types 2A and 2B based on the presence of missense mutations in the RET protooncogene. Kindred members who have inherited these syndromes can be identified before clinical or biochemical evidence of medullary thyroid carcinoma (MTC) develops, the malignancy that occurs in all affected patients. It is not known whether prophylactic removal of the thyroid gland early in childhood, based on a positive genetic test result, has a better clinical outcome than that associated with thyroidectomy after MTC is diagnosed clinically or biochemically. The authors' goal was to determine the long-term outcome for patients with MEN 2A and 2B who had thyroidectomy for MTC during childhood. These results were compared with those of patients who had prophylactic removal of the thyroid gland after the genetic diagnosis of MEN 2A was established. The hospital records of 49 children with MEN 2A or 2B were reviewed. Each patient had thyroidectomy for MTC before 16 years of age. The mean age at the time of operation was 10 years, and the mean follow-up period for those who had surgery before the availability of direct DNA genetic testing was 9.8 years. The indications for surgery included an elevated basal or stimulated plasma calcitonin level, a positive genetic test result, a thyroid mass, family history of MTC, or a phenotype diagnostic of MEN 2B. All children for whom the diagnosis of MEN 2A was established by direct genetic testing had thyroidectomy within the last 2 years. Of the 11 patients with MEN 2B who underwent thyroidectomy during childhood, 10 had MTC, and only 3 (27%) remain free of disease after the mean follow-up period of 11 years. One patient died, and seven are alive with persistent MTC. Among the 24 patients with MEN 2A who had their thyroid glands removed because of a family history of MTC or because of biochemical evidence of the disease, 5 (21%) have persistent or recurrent MTC after the mean follow-up period of 9.3 years. In four of these, the MTC was confined to the thyroid gland at the time of thyroidectomy. Of the 14 children who had thyroidectomy based on direct DNA testing, MTC was present in 11. Only four had elevated levels of stimulated plasma calcitonin before surgery. None had lymph node metastasis or surgical complications. The authors conclude that a significant number of patients with MEN 2A or 2B who undergo thyroidectomy in childhood for MTC have persistent or recurrent disease long-term. The genetic diagnosis of patients with these syndromes may allow for prophylactic surgery before the development of biochemical or clinical evidence of MTC. This approach is safe, but longer clinical follow-up will be necessary to confirm that MTC has been cured.

Diagnosis of multiple endocrine neoplasia [MEN] 2A, 2B and familial medullary thyroid cancer [FMTC] by multiplex PCR and heteroduplex analyses of RET proto-oncogene mutations

Multiple endocrine neoplasia type 2 [MEN 2] is an autosomal dominant cancer syndrome with two subtypes, 2A and 2B. MEN 2A and medullary thyroid cancer [MTC] are caused by > 25 different point mutations in exons 10, 11, and 13 of the RET proto-oncogene, whereas MEN 2B is caused by a single exon 16-point mutation. Various molecular methods have been used to identify the different mutations, including DNA sequencing, restriction enzymatic analyses, chemical cleavage mismatch, Single Stranded Conformational Polymorphism [SSCP], and Denaturing Gradient Gel Electrophoresis [DGGE]. These techniques, although useful and accurate, are labor intensive and some involve the use of radioactivity. We have developed a multiplex PCR assay simultaneously to amplify exons 10, 11, and 13 of the RET proto-oncogene. The multiplex PCR product is then analyzed on a modified Mutation Detection Enhancement [MDE] matrix for heteroduplex identification and visualized with ethidium bromide. Distinct heteroduplexes were detected for each known RET proto-oncogene mutation available in our laboratory (nine in exon 10, five in exon 11, one in exon 13, and the single exon 16 mutation). Presymptomatic DNA diagnosis of MEN 2 is essential since pentagastrin-stimulated calcitonin studies can occasionally produce false positive results and lead to unnecessary thyroidectomies. Prophylactic thyroidectomy is recommended by age 5 or 6 once a mutation is identified in a patient, since penetrance is very high. MDE heteroduplex detection provides a quick, efficient, and inexpensive method of screening for RET mutations in MTC patients with unknown mutations, or for presymptomatic diagnosis in individuals at risk for inheriting a known RET mutation. Confirmation of the specific mutation can be achieved by restriction enzymatic digestion (if feasible) or by DNA sequencing.

Early treatment of hereditary medullary thyroid carcinoma after attribution of multiple endocrine neoplasia type 2 gene carrier status by screening for ret gene mutations

BACKGROUND

Germline missense point mutations of the ret proto-oncogene have been shown as causative in multiple endocrine neoplasia type 2 (MEN 2A and 2B) and in familial medullary thyroid carcinoma (FMTC). Most of the mutations are found in exon 10, 11, or 16 of the gene and are easily recognized by restriction analysis.

METHODS

Using restriction analysis, we screened 58 subjects from nine kindreds.

RESULTS

Family members (n = 16) already known to be affected with the disease carried the germline mutation. Among the 42 subjects apparently unaffected, 37 were not gene carriers and 5 were gene carriers. Basal and pentagastrin-stimulated serum calcitonin levels were normal in two patients and abnormal in three. All patients were treated with total thyroidectomy and central node dissection. In all cases multiple foci of MTC were shown at histologic examination.

CONCLUSIONS

Our data indicate that genetic screening of MEN2 pedigrees allows the early identification of gene carriers. Because surgery of MTC in the preclinical phase has high probability of curing these patients, we suggest genetic screening soon after birth and total thyroidectomy in gene carriers as early as possible.

No mutation at codon 918 of the RET gene in a family with multiple endocrine neoplasia type 2B

Multiple endocrine neoplasia type 2B (MEN 2B) is a rare cancer syndrome which is inherited in an autosomal dominant manner. The molecular basis of this condition has recently been defined as a mutation of codon 918 of exon 16 of the RET proto-oncogene. The mutation in codon 918 has been described in 69 out of 72 families with MEN 2B. We have studied a brother and sister who undoubtedly have the features of MEN 2B as evidenced by medullary thyroid carcinoma, phaeochromocytoma, mucosal neuromas and skeletal abnormalities. Neither of these patients has the classic gene mutation at codon 918 of exon 16 of the RET proto-oncogene, and although exons 2-20 have also been sequenced, no abnormality has been found. DNA analysis is a sensitive method of screening families for the MEN 2 syndromes. The absence of the mutation at codon 918 in a phenotypically normal individual would refute the diagnosis of MEN 2B, but in an individual with some of the features of MEN 2B would make the clinician reconsider the diagnosis. This family demonstrates that, although it is rare, the absence of the mutation in codon 918 of exon 16 of the RET proto-oncogene does not always exclude the diagnosis of MEN 2B. In such families routine biochemical screening for medullary thyroid carcinoma and phaeochromocytoma must be maintained for all individuals at genetic risk.

Presymptomatic DNA screening in families with multiple endocrine neoplasia type 2 and familial medullary thyroid carcinoma

BACKGROUND

Missense mutations of the ret proto-oncogene on chromosome 10q11.2 are the underlying cause of hereditary medullary thyroid carcinoma (MTC), either as familial MTC only (FMTC) or as a part of multiple endocrine neoplasia type 2 syndrome (MEN 2). This study presents our experience with direct presymptomatic DNA screening in MEN 2 and FMTC kindreds.

METHODS

Twenty one families with MEN 2 or FMTC were considered in the study. One hundred three individuals had been analyzed; 56 were at risk. The ret mutations were detected by DNA analysis of exons 10, 11, and 16 by using nonradioactive labeling method based on digoxigenin DNA sequencing technique. Serum calcitonin evaluation was carried out in all individuals at risk. Thyroidectomy was performed in those who had to undergo surgery.

RESULTS

The ret mutations were identified in all 21 families. In MEN 2A and FMTC families mutations occurred in exons 10 and 11. MEN 2B families had mutations in exon 16. The most frequent mutation in MEN 2A and FMTC affected codon 634. Twenty one gene carriers were identified in unaffected individuals at risk. Ten of 21 gene carriers had elevated calcitonin levels, and 11 had normal levels. MTC or C-cell hyperplasia was found in six gene carriers with pathologic calcitonin values who underwent operation. In a 5-year-old gene carrier with normal calcitonin values C-cell hyperplasia was evident.

CONCLUSIONS

Direct predictive DNA analysis allows us to identify MEN 2 or FMTC gene carriers and offer them prophylactic treatment.

From medical history and biochemical tests to presymptomatic treatment in a large MEN 2A family

An extensive study was published in 1959 in the Netherlands on a large family, which initially attracted attention because of a family history of attacks of shaking. Clinical investigation revealed phaeochromocytomas in four family members. In 1975, the family was identified to be a MEN 2A family, and since then, the members were examined annually using measurement of catecholamine metabolites in 24-h excreted urine and C-cell stimulation tests. In 1993, the RET proto-oncogene on chromosome 10q11 was found to be associated with MEN 2A and a specific mutation in this gene was identified in the family. In this family, 32 MEN 2A patients were detected. Since screening started in 1975, no patient died of phaeochromocytoma; however, two patients died of metastasized medullary thyroid carcinoma (MTC) (mean age 46 years). Twelve patients were operated on for phaeochromocytoma, and 13 for MTC. The results of DNA-analysis revealed the failures of the biochemical tests to identify affected family members. Six disease gene carriers with normal C-cell stimulation test results appeared to have small multifocal MTCs. Two carriers with normal excretion levels of catecholamines had a small phaeochromocytoma. DNA-analysis enables the unambiguous diagnosis of MEN 2A gene carrier-ship, allowing presymptomatic surgery for MTC.

Medullary thyroid carcinoma: recent advances and management update

Medullary thyroid carcinoma (MTC) is a malignancy of the thyroid C-cells that comprises 5-10% of all thyroid cancers. MTC occurs in both sporadic and familial forms, the latter making up 25% of all MTCs and being comprised of three distinct syndromes--multiple endocrine neoplasia type 2A (MEN 2A), multiple endocrine neoplasia type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). To date, screening for MTC has been performed using the pentagastrin stimulation test, which is a provocative test for calcitonin release. Germline mutations in the RET protooncogene have been identified in families manifesting these syndromes and genetic screening of individuals at risk of one of these syndromes has become integral to their clinical management. The majority of the mutations associated with MEN 2A and FMTC are tightly clustered in a cysteine-rich region of the RET receptor. A single mutation associated with MEN 2B is in the the tyrosine kinase domain of the RET receptor. Somatic mutations have been identified in the tumor tissue of individuals with sporadic MTC and may prove to be helpful markers in discerning the hereditary or sporadic nature of the MTC. There is general agreement that the primary operation for MTC should include total thyroidectomy and central neck lymph node clearance. The role of microdissection for recurrent disease awaits longitudinal evaluation. External radiotherapy, radionuclide therapy, and chemotherapy may have a role in palliation, but have not been proven to have a curative value. Prognostic factors are discussed.

Analysis of RET protooncogene point mutations distinguishes heritable from nonheritable medullary thyroid carcinomas

BACKGROUND

The distinction of sporadic from inherited medullary thyroid carcinomas (MTCs) is of clinical importance because of the differences in prognosis, and the need for family screening for genetic counseling required in the latter. Germline mutations in the RET protooncogene are associated with multiple endocrine neoplasia (MEN) type 2A, familial medullary thyroid carcinoma (FMTC), and MEN type 2B. Somatic point mutations in the same gene have been identified in a subset of sporadically occurring medullary thyroid carcinomas.

METHODS

A nonisotopic polymerase chain reaction-(PCR) based single strand conformation polymorphism (SSCP) analysis and heteroduplex gel electrophoresis method was used to screen DNA extracted from 32 formaldehyde fixed and paraffin embedded MTC specimens and normal tissue or blood of the same patient for point mutations in RET exons 10, 11, and 16. Point mutations were identified by nonisotopic cycle sequencing of PCR-products using an automated DNA-sequencer. Results were compared with the disease phenotype, clinical findings, and follow-up.

RESULTS

Six different missense germline mutations were identified at cysteine residues 618, 630, and 634 of the cysteine-rich extracellular RET domain encoded by exons 10 and 11 in all patients with FMTC and MEN 2A. The frequency of mutations at codon 634 was higher in patients with MEN 2A than with FMTC and a 634 Cys-->Arg mutation was associated with parathyroid disease in three patients. A germline Met-->Thr point mutation at codon 918 of the RET tyrosine kinase domain was identified in all three patients with MEN 2B. Two patients with clinically sporadic MTCs and negative family history exhibited a RET germline mutation at codon 634, indicating the presence of an nonpredicted inherited MTC. Furthermore, one patient had a 618 Cys-->Ser mutation in the tumor and nontumorous thyroid DNA but not in blood DNA, indicating a mosaic mutation affecting thyroid tissue but not blood cells. Tumor specific (somatic) Met-->Thr point mutations at codon 918 were identified in 5 of 13 sporadic MTCs. The remaining eight sporadic MTCs lacked mutations in all three RET exons tested.

CONCLUSIONS

This study demonstrates that (1) the molecular methods are not only suitable to identify asymptomatic individuals at risk for MEN 2A, FMTC, and MEN 2B but also to distinguish heritable from nonheritable MTCs using archival tissue specimens, and (2) that more MTCs than clinically expected are heritable, indicating the need for genetic analysis of all patients with MTC.

RET proto-oncogene mutations in multiple endocrine neoplasia type 2 and medullary thyroid carcinoma

The identification of RET proto-oncogene mutations in patients with MEN2 2 years ago was a watershed event in the management of this genetic cancer syndrome. The identification of a finite number of mutations that together causes more than 95% of hereditary and 15-25% of sporadic MTC has made it possible to develop simple and definitive tests to screen individuals at risk for this tumour syndrome. The impact of this technology is enormous. It is now possible to reassure 50% of family members at risk that they, and their children, do not have to worry about developing MTC. In the other 50% who are gene carriers, it is now possible to approach clinical management with greater certainty and plot strategies that are likely to result in a greater percentage of curative therapy. It seems likely that this technology will also have an impact on the management of sporadic MTC, although it is still too early to define a specific role for mutational analysis in these patients, except to exclude hereditary disease. The identification of specific mutations causative for MTC makes it possible to conceive future strategies for the treatment or prevention of MTC and to further extend the impact of these exciting findings.

Advances in the management of patients with thyroid disease

Discoveries related to thyroid immunology, especially concerning the thyroid-stimulating hormone (TSH) receptor, may facilitate new immunologic approaches to the therapy of Graves' disease and the thyroiditis syndromes. Advances in genetics are being applied to the thyroid hormone resistance syndromes and papillary and medullary carcinomas. The development of ever more sensitive TSH assays has led to the detection of subclinical thyroid disease, which has special implications for the sick and elderly patients. Sensitive TSH assays also allow more precise titration of levothyroxine (T4) dosages, especially for patients with a past history of thyroid cancer. Evidence continues to accumulate suggesting that postmenopausal women on T4 doses that suppress the TSH level below 0.1 ulU/mL have lower bone mineral density than matched patients with healthy TSH levels. Also, pregnant hypothyroid women need higher T4 doses to normalize the TSH levels. In the evaluation of thyroid nodules, fine-needle aspiration biopsy is the single most definitive modality in selecting the patients for surgery. Scintigraphy provides a complimentary role, especially in defining autonomously functioning thyroid adenomas (AFTA), because these should not be treated with T4 suppression. Ultrasound-guided needle biopsy is occasionally helpful with nodules that are difficult to palpate. Concern for possible tracheal compression after treatment of toxic multinodular goiter with large doses of radioactive iodine (I-131) in the range of 50 to 150 mCi (1.85 to 5.5 GBq) does not seem warranted. Work, primarily out of Italy, suggests AFTA can be ablated with repeat ethanol injections. Residual tissues after thyroidectomy for differentiated carcinoma can be "stunned" by tracer doses of 131I greater than 3.0 mCi (111 MBq), which diminishes the uptake and effectiveness of a subsequent therapy dose. Positron emission tomograph, imaging with thallium-201, and Technetium 99m Sestamibi can identify a small number of patients shown to have metastases from differentiated thyroid carcinoma by increasing thyroglobulin levels in the absence of 131I uptake. Several groups have recently advocated treating such patients empirically with 131I.

Low frequency of germline mutations in the RET proto-oncogene in patients with apparently sporadic medullary thyroid carcinoma

BACKGROUND AND OBJECTIVES

Medullary thyroid carcinoma (MTC) occurs both sporadically and in the autosomal dominantly inherited multiple endocrine neoplasia (MEN) type 2 syndromes. The distinction between true sporadic MTC and a new mutation familial case is important for future clinical management of both the patient and family. The susceptibility gene for MEN 2 is the RET proto-oncogene. Systematic analysis for germline mutations of the RET proto-oncogene was performed in a series of 67 patients with apparently sporadic MTC to determine whether they were true sporadic cases or unsuspected de novo MEN 2 cases.

DESIGN AND PATIENTS

Sixty-seven unselected patients with sporadic MTC were randomly ascertained from clinic patients from four centres. The diagnosis of MTC was confirmed by histopathology. Germline DNA was extracted from peripheral blood leucocytes or from paraffin-embedded tissue and subsequently used for polymerase chain reaction amplification.

MEASUREMENTS

Polymerase chain reaction based RET mutation analysis was performed by direct double-stranded cycle sequencing of exons 10, 11, 13 and 16, within which the majority of MEN2 mutations have been shown to occur.

RESULTS

In this series, there was one proven case of germline mutation in RET codon 620, which previously has been shown to be responsible for MEN 2, thus indicating heritable disease. No germline mutation in codon 918, typical of MEN 2B, was found.

CONCLUSIONS

A figure of 1.5% germline mutations in 67 apparently sporadic MTC is lower than the incidence of familial disease reported in previous series involving clinical and biochemical screening. The presence of a germline mutation in the RET proto-oncogene in a patient with MTC indicates heritable disease. The absence of germline RET exon 10, 11, 13 or 16 mutation appears to rule out MEN 2A to a high probability, although the presence of a familial form of MTC other than classical MEN 2A cannot be excluded conclusively.

Thyroid growth factors, signal transduction pathways, and oncogenes

Growth of thyroid cancer cells is stimulated by various growth factors via signal transduction pathways. TSH, EGF, IGF, and TGF-alpha stimulate and TGF-beta inhibits thyroid cell growth. TSH stimulates thyroid cells via both the adenylate cyclase-PKA and the PLC-PKC-Ca signal transduction pathways. TSH-r, ras, gsp, ret, trk, and myc are oncogenes that are activated in some thyroid neoplasms. P53 and RB are tumor suppressor genes that are inactivated in some thyroid cancers.

Presymptomatic genetic screening in families with multiple endocrine neoplasia type 2

Medullary thyroid carcinoma occurs sporadically or as a part of the inherited cancer syndrome multiple endocrine neoplasia (MEN) type 2. The MEN 2 gene has been identified as the RET proto-oncogene on chromosome 10. In MEN 2A, RET mutations are detectable in one of five cysteine codons within exons 10 and 11 and in MEN 2B in codon 918 (exon 16). Direct DNA testing for RET proto-oncogene mutations is the method of first choice in presymptomatic screening of MEN 2 families. Gene carriers should be offered prophylactic thyroidectomy. The process of DNA analysis for RET proto-oncogene mutations is demonstrated in one family with hereditary medullary thyroid carcinoma. RET mutations were detectable in five of the nine family members at risk.

Microsatellite instability: new aspects in the carcinogenesis of colorectal carcinoma

Very recently a new molecular mechanism in the tumorigenesis of colorectal carcinoma has been described which is closely linked to hereditary non-polyposis colonic cancer (HNPCC). Ubiquitous changes in the length of simple repetitive DNA sequences between constitutional and tumour DNA occur in about 90% of cases of HNPCC and in about 15% of cases of non-familial, sporadic colorectal carcinoma. Such microsatellite instabilities have been shown to be the phenotypical marker of mutations in the human homologues of prokaryotic mismatch repair genes (MutS, MutL, MutH). These data provide crucial new tools in the detection of patients at high risk of developing colon cancer and other HNPCC-related carcinomas. In addition, these developments provide new insights into a new, presumably primary event in oncogenesis, i.e. the occurrence of mutations in genomic stability genes leading to an increased cellular mutation rate ("mutator phenotype") and thus to cancer.

Molecular Diagnosis of Multiple Endocrine Neoplasia (MEN) in Paraffin-Embedded Specimens

In this article, we summarize our recent findings on rearranged during transfection (RE7) mutations in a series of 46 sporadic as well as multiple endocrine neoplasia (MEN) type 2- associated tumors and present results of our family screening efforts to identify MEN 2 and MEN 1 gene carriers. A nonisotopic polymerase chain reaction-based single-strand conformation polymorphism (PCR-SSCP) analysis and heteroduplex gel electrophoresis method was used to screen DNA extracted from archival specimens of 22 patients with MEN 2-associated and 24 patients with sporadic tumors for mutations in RETexons 1O, 11, 13, and 16. Point mutations were identified by nonisotopic cycle sequencing of PCR products using an automated DNA sequencer. We found six different missense germ line mutations at cysteine residues encoded by exons 10 and 11 in all patients with MEN 2A or familial medullary thyroid carcinoma (FMTC). The frequency of mutations at codon 634 was higher in patients with MEN 2A than with FMTC and a (63)Cys - Arg mutation was associated with parathyroid disease. A germline Met -* Thr point mutation at codon 918 of the RETtyrosine kinase domain encoded by exon 16 was identified in all MEN 2B patients. Nonpredicted inheritable medullary thyroid carcinomas (MTCs) were detected in two patients and a mosaic postzygotic mutation was found in one additional patient. Tumor-specific (somatic) Met - Thr point mutations at codon 918 were identified in 5 of 13 sporadic MTCs and 2 of 8 sporadic pheochromocytomas (PCCs). The remaining sporadic tumors lacked mutations in all four RET exons tested. In exon 13, a nucleic acid polymorphism (CTT/CTG; Leu) at codon 769 was identified, which is present in approx 40% of the examined population. Our study demonstrates that the molecular methods used are not only suitable to identify asymptomatic individuals at risk for MEN 2A, FMTC, and MEN 2B, but also to distinguish sporadic from inherited tumors using archival tissue specimens; and that more tumors than clinically expected are inheritable, indicating the need for genetic analysis of all MTC and PCC patients.