5979

RET

CDHF12|CDHR16|HSCR1|MEN2A|MEN2B|MTC1|PTC|RET-ELE1|RET51;ret proto-oncogene;RET;ret proto-oncogene

RET transforming sequence|cadherin family member 12|cadherin-related family member 16|hydroxyaryl-protein kinase|proto-oncogene c-Ret|proto-oncogene tyrosine-protein kinase receptor Ret|receptor tyrosine kinase|ret proto-oncogene (multiple endocrine neopl

10q11.2

protein-coding

OBJECTIVE: Evaluation of prophylactic total thyroidectomy in childhood in case of MEN2A gene carriership. DESIGN: Retrospective. METHOD: Prophylactic thyroidectomy was performed in 14 MEN2A gene carriers (7 boys, 7 girls; median age 9.1 year (range: 4.8-14.7)), in June 1993-July 1997 at the department pediatric Surgery of the Wilhelmina children's Hospital in Utrecht, the Netherlands. Median time between genetic investigation and operation was 5.5 months (range: 2-35). Lymph node dissection was not performed. The parathyroids were identified and left untouched as far as possible, autotransplantation was performed twice because ofdoubt about viability. Outpatient follow-up took place every 3-6 months. RESULTS: One patient (13.4 year) showed macroscopic, the other 13 microscopic multifocal medullary thyroid carcinoma, 11 bilateral and 3 unilateral. In 1 child (6.2 year) neuroinvasive growth existed already. Surgical sections were free of tumour. After the operation temporary hoarseness occurred once, temporary hypocalcaemia three times and permanent hypoparathyroidism twice; after autotransplantation nohypocalcaemia occurred. Median follow-up was 3.2 year (range: 1 month-4.0 year).Mild psychological problems were observed in 4 patients, psychiatric problems in1. CONCLUSION: Prophylactic total thyroidectomy during the first decade is recommended. Additional lymph node dissection and total parathyroidectomy are unnecessary than. In order to prevent postoperative hypoparathyroidism, autotransplantation of at least one parathyroid is advisable.

BACKGROUND: Patients with multiple endocrine neoplasia (MEN) type 2 are at risk for early medullary thyroid carcinoma (MTC). Recently, the cloning of the ret oncogene has made it possible to identify patients at risk for MEN 2 syndrome with a high degree of reliability before presenting any symptoms. METHODS: children of families with MEN 2 were screened genetically if one of the parents was a known gene carrier of the RET proto-oncogene. If they were carriers, thyroidectomy was performed. RESULTS: The authors report five children with MEN 2 who underwent prophylactic thyroidectomy irrespective of the results of calcitonin screening tests after genetic screening had shown that they were carrier of the RET proto-oncogene. Apart from a temporary hypocalcemia in one, the operations were uneventful. Pathology results showed MTC in three children of one family with MEN 2A at age 2, 3, and 6 years. In two families with MEN 2B thethyroidectomy specimen showed bilateral MTC in a 1-year-old and a 3-year-old child. CONCLUSIONS: These findings show that MTC occurs at very young age in children with MEN 2. The authors advocate performing prophylactic thyroidectomy in the first year of life in children with MEN 2B and at age 2 years in childrenwith MEN 2A to obtain an optimal cure rate.

BACKGROUND: mutations of the RET proto-oncogene co-segregate with multiple endocrine neoplasia type 2A. A rare sequence abnormality at codon 804 (c804) hasbeen reported in 6 kindreds and linked to mild C-cell disease, which raises the question of the appropriateness of thyroidectomy in childhood. The purpose of this study was to (1) report the clinical correlates of 5 additional c804 kindreds, and (2) clarify therapeutic options in children. METHODS: Thirty-eightmembers from five c804 kindreds underwent genetic analysis. Biochemical, operative, and pathology reports were reviewed. RESULTS: Twenty-three gene carriers were identified, of whom 14 had thyroidectomy. Medullary thyroid carcinoma was found in 7 patients (aged 5-56 years), C-cell hyperplasia in 6 patients (aged 13-40 years), and normal histology in a single patient (aged 27 years). One patient with medullary thyroid carcinoma died of metastases (aged 12years). Nine of the 23 gene carriers delayed operation, 4 of whom had calcitonintesting. Three of the 4 patients had abnormal calcitonin levels and a single patient was negative (aged 40 years). Of the remaining 9 patients, 2 await thyroidectomy, and 3 have refused evaluation. CONCLUSIONS: Penetrance of the c804 mutation is highly variable. Medullary thyroid carcinoma associated with this genotype has aggressive potential. Prophylactic thyroidectomy in childhood is a viable approach.

OBJECTIVE: Both multiple endocrine neoplasia type 2A (MEN 2A) and familial medullary thyroid carcinoma (FMTC) are caused by germline mutations of the RET proto-oncogene. A broad spectrum of malignancy within and between families has been described with no clear genotype-phenotype correlation due to a scarcity ofavailable data of large kindreds. DESIGN: Here we present the only known family with a germline mutation of codon 611 TGC to TTC (exon 10) in the RET proto-oncogene leading to a replacement of cysteine by phenylalanine (Cys611Phe or C611F). RESULTS: Twenty family members of this large kindred are gene carriers (GCs) and seven (5-13 years old) are potential carriers but have yet to be analysed. The clinical course of medullary thyroid carcinoma (MTC) in this family is characterized by a very slow evolution and progression of the tumour with no MTC-related death to date. Of 11 patients (30-69 years old) having undergone thyroidectomy six were classified as pT1, four as pT2 and one as C-cell hyperplasia according to the TNM system of the International Union Against cancer. Due to cervical and mediastinal lymph node metastasis one patient (44 years old) had to be operated on a second time. The seven non-operated GCs of the fourth and fifth generation (17-26 years old) are yearly monitored with pentagastrin stimulation tests; one non-operated GC (43 years old) has refused any further investigations. Screening for primary hyperparathyroidism and phaeochromocytoma was negative in ALL cases. CONCLUSION: We suggest from these experiences that the general advice for thyroidectomy in early childhood should be modified in certain families, depending on genotype.

Medullary thyroid cancer (C.M.T.) can be a sporadic form generally in adults or a heredofamilial form where the first symptom appears in pediatric and adolescent age. The hereditary form can be isolated or associated with others endocrine neoplasias of type 2: MEN2a (with or without cutaneous lichen amyloidosis) and MEN2b. The responsible gene of the transmission has been identified in proto-oncogene RET localized on chromosome 10. Point form mutations of this proto-oncogene have been found on exons 10 and 11 in MEN2a and on 16 in MEN2b. In our study on 64 subjects, who belong 11 familiar groups, affected by MEN2a, MEN2b and familiar C.M.T., underwent a genetic research to look for point form mutations of proto-oncogene RET with PCR followed by the analysis of restriction. A genetic mutation has been revealed in 25 subjects: 18 were already known affected by MEN2 and so surgical treated and 7 seemed healthy (mean age 17.4 years, range 10-25). These 7 patients has been undergone clinical research and surgical treatment: a total thyroidectomy associated a lymphectomy of the central compartment. In ALL cases the histological exam showed C.M.T. moreover a patienthad metastasis in lymph nodes of the central compartment. Another had hyperparathyroidism and pheochromocytoma treated with total thyroidectomy, parathyroidectomy and bilateral laparoscopic adrenalectomy. The identification in a very early age of carrier subjects of hill's gene inside an affected family, permits the execution of a prophylactic total thyroidectomy to prevent the C.M.T.. The penetrance of this neoplasia in hereditary form is 100%.

Neuroblastoma is a neural crest-derived tumor of childhood with a serious prognosis; only 20% of patients with stage 4 disease survive 5 years from diagnosis. Mechanisms involved in neuroblastoma development are unclear, but theengagement of many neuroblastoma-related gene(s) is suggested by specific chromosomal alterations. Most prominent among these is the amplification of the MYCN oncogene and the deletion of the 1p36 region. Other genetic aberrations have been discovered over the years such as deletions of 11q and 14q and gain of 17q.Although tumor aggressiveness greatly depends on the most frequent genetic abnormalities, to date no neuroblastoma-related gene has been discovered. Neuroblastoma usually occurs sporadically, but 1.5% of ALL diagnosed cases show familial recurrence with an autosomal dominant inheritance and incomplete penetrance. A comparison between hereditary and sporadic neuroblastomas led Knudson and Strong to gather that the two-hit hypothesis, proposed for retinoblastoma, could be applied to neuroblastoma. To determine if the 1p36 region harbors a predisposition gene for familial neuroblastoma, we carried out linkage analysis at 1p36 loci in two families with recurrent neuroblastoma. Similarly, we analyzed loci of chromosome 16, where a predisposition locus was recently mapped. We also analyzed markers located close to several candidate genes (RET, NF1, GDNF, GFRA1, EDNRB, and EDN3) involved to a different extent inother neurocristopathies. Our findings indicate that the candidate chromosomal regions and genes analyzed are not in linkage with neuroblastoma.

Both external and internal exposure to radiation have been linked to the development of papillary thyroid cancer. Rearrangement of the gene for RET tyrosine kinase and subsequent expression of this protein has also been found tooccur in many papillary thyroid cancers, and with increased frequency in radiation-related cancers following the Chernobyl accident. However, little has been reported on the frequency of RET rearrangements in cancers after exposure to external radiation. We here report on RET protein immunoreactivity in paraffin-embedded thyroid samples from 30 patients with papillary thyroid cancerwho received radiation treatment during childhood for benign conditions at Michael Reese Hospital in Chicago, and in 34 patients identified from the tumor registry as having papillary thyroid cancer with no history of therapeutic radiation. The subjects were characterized by sex, age at surgery, and the following attributes of tumor pathology: size, number of lobes involved, number of foci, lymph node metastases, and soft tissue invasion. Representative tissue samples were reacted with an antibody against the RET tyrosine kinase domain whose expression has been shown to correlate highly with RET/PTC rearrangements.A greater percentage of cancers positive for RET immunoreactivity was found in the radiation-exposed group (86.7% vs. 52.9%, P = 0.006). Although the mean age at surgery of the exposed group was lower than the control group, there was no correlation of positive RET immunoreactivity with the age at surgery. No characteristics of the tumors were associated with positive RET immunoreactivity. In summary, the greater incidence of RET-immunopositives in the irradiated groupindicates that the expression of RET immunoreactivity is strongly associated with radiation exposure, but the prognostic significance of this is not yet clear.

Thyroid epithelial cells frequently express one or more members of the rearranged during transfection/papillary thyroid carcinoma (RET/PTC) fusion oncogene familyduring early stages of cancer, and fusion gene transcripts have been found in inflammatory conditions of the thyroid such as the autoimmune disease, Hashimoto's thyroiditis. Because these oncogenes encode chimeric proteins, novelRET/PTC epitopes may be targets of antitumor immune responses. We have been interested in the RET/PTC3 (RP3) fusion protein because this family member is more frequently expressed in radiation-induced and childhood papillary carcinomas than other members of the fusion oncogene family. We hypothesized that the activated kinase of c-RET, in the form of RP3, when expressed in patients with thyroid disease, presents an unusual altered self target for T cell recognition.Interestingly, we find that immunization with mouse RP3 protein can induce a strongly immunogenic response to RP3, although this response is not directed against the peptide comprising the unique fusion region. Rather, the responses are specific for the carboxyl-terminal portion of RP3 that is derived from the self protein c-RET. Furthermore, transplantation of RP3-expressing thyroid tumors into naive mice resulted in leukocytic infiltration, tumor rejection, and induction of RP3-specific T cells. Thus, the somatic fusion of two unrelated self proteins results in the development of a uniquely immunogenic response directed against self epitopes within RP3. These studies may better define the mechanismscontrolling the initiation of thyroid-specific immune responses and provide insight into the design of novel molecules for invoking tumor-specific immunity.

OBJECTIVES: The aim of this study was first to investigate whether early total thyroidectomy (ETT; 1-5 years of age) can prevent medullary thyroid carcinoma with persistent or recurrent disease (PRD) in pediatric patients with multiple endocrine neoplasia type 2A (MEN-2A) and second, to evaluate the strength of codon analysis in children with MEN-2A as prognostic parameter. METHODS: Case reports and review of the literature for pediatric patients with MEN-2A were conducted. Inclusion criteria were age (0-20 years) and histologic degree of C-cell disease (normal = N, C-cell hyperplasia = CCH, medullary thyroid carcinoma = MTC, metastatic MTC = MMTC). To evaluate therapeutic results of ETT (1-5 years) versus late total thyroidectomy (LTT; 6-20 years), age-dependent histologic stages of C-cell disease and postoperative occurrence of PRD were compared. Prognostic value of specific codons, age-dependent histologic distribution, and long-term outcome were analyzed. RESULTS: In a total of 260 cases, 42 (16%) underwent ETT, and 218 (84%) underwent LTT. Histologic analysis showed significant difference between ETT versus LTT (57% vs 76%) regarding malignant stage of C-cell disease (of combined rate of MTC and MMTC). Long-term outcome was documented in 74 patients (28%). During a median follow-up period of 2 years (range: 0-15 years), 21 of 65 of the LTT group versus 0 of 9 of the ETT group suffered PRD. Information about codon analysis was available in 150 patients (58%). Mutated codons were c634 (63%), c618 (19%), c620 (9%), and c804 (6%). Codon-related histologic analysis resulted in prognostic differences: 81% of patients with c634-mutation had MCT or MMTC in contrast to c804 (44%), c618 (34%), and c620 (7%). Fifteen of 17 MMTC and 7 of 9 PRD occurred in patients with c634-mutation. CONCLUSIONS: 1) ETT until 5 years of age in MEN-2A gene carriers results in significant reduction of MTC and MMTC in favor of CCH and improved disease-free long-term outcome. 2) Codon analysis is an important prognostic factor. Timing of TT could be individualized based on codon-specific prognosis. Until more detailed knowledge is available, consequent genetic and biochemical screening is mandatory for appropriate individual timing of ETT before age of 5 years.

In the present study we review ENT tumor pathology in childhood. Only the most salient aspects are emphasized and the variety of entities reviewed was restricted. Molecular biology techniques reveal infection by human papilloma virus (types 6 and 11) in 50 % of papillomas, while immunohistochemical techniques are less effective in papilloma virus detection. The myofibroblastic nature of nasal angiofibroma has been demonstrated and its incidence is 25 timesmore frequent in patients with familial polyposis of the colon. Overexpression of p53 occurs in the initial stages of nasopharyngeal carcinoma, while overexpression of c-myc is correlated with an unfavorable prognosis. Recently, olfactory neuroblastoma has been shown not to express the protein product of theMIC-2 gene (antibody 12E7), thus the hypothesis that it could be a member of theEwing tumor family (neuroectodermal peripheral tumors) has not been confirmed, although it is a primitive neural tumor. The head and neck rhabdomyosarcoma withthe best prognosis is that located in the orbit, and cytogenetic studies have shown chromosomic translocation t(2;13) in 50 % of these childhood tumors when they are of the alveolar-type, while trisomy of chromosome 2 or 20 is more characteristic of the embryonic-type. Currently, any classifying features of ENTlymphomas must be based on the Revised European-American Classification of Lymphoid Neoplasms (REAL). Papillary and medullary carcinomas are the most common histological types of thyroid carcinoma in childhood. Alterations in ret/PTC play a significant role in the pathogenesis of both.

In the present study we review ENT tumor pathology in childhood. Only the most salient aspects are emphasized and the variety of entities reviewed was restricted. Molecular biology techniques reveal infection by human papilloma virus (types 6 and 11) in 50 % of papillomas, while immunohistochemical techniques are less effective in papilloma virus detection. The myofibroblastic nature of nasal angiofibroma has been demonstrated and its incidence is 25 timesmore frequent in patients with familial polyposis of the colon. Overexpression of p53 occurs in the initial stages of nasopharyngeal carcinoma, while overexpression of c-myc is correlated with an unfavorable prognosis. Recently, olfactory neuroblastoma has been shown not to express the protein product of theMIC-2 gene (antibody 12E7), thus the hypothesis that it could be a member of theEwing tumor family (neuroectodermal peripheral tumors) has not been confirmed, although it is a primitive neural tumor. The head and neck rhabdomyosarcoma withthe best prognosis is that located in the orbit, and cytogenetic studies have shown chromosomic translocation t(2;13) in 50 % of these childhood tumors when they are of the alveolar-type, while trisomy of chromosome 2 or 20 is more characteristic of the embryonic-type. Currently, any classifying features of ENTlymphomas must be based on the Revised European-American Classification of Lymphoid Neoplasms (REAL). Papillary and medullary carcinomas are the most common histological types of thyroid carcinoma in childhood. Alterations in ret/PTC play a significant role in the pathogenesis of both.

Genetic risks related to paternal age should be of interest to clinical andrologists counselling older men who wish to father a child. Theoretically, the number of (pre-meiotic) mitotic cell divisions during spermatogenesis and their remarkable increase with ageing compared with oogenesis would be in favour of genetic risks for the offspring of older men. But for numerical and structural chromosomal anomalies, such an influence of paternal age has not been found. However, in several autosomal dominant disorders affecting three specific genes (fibroblast growth factor receptor 2 and 3, RET proto-oncogene) the risk for a child to be affected increases with paternal age at time of birth. For other autosomal dominant -X chromosomal dominant or recessive disorders, the availabledata are sufficient to support the concept of a positive relationship between paternal age and de novo gene mutations. Studies analysing gene sequences of affected children and their parents would allow further evaluation of this topic. The impact of paternal age on disorders with a complex genetic background, however, is a matter of debate. A significant effect of paternal age could not be shown for nonfamilial Alzheimer's disease, congenital heart defects, nonfamilialschizophrenia, acute lymphoblastic leukaemia or prostate cancer.

The gene predisposing to multiple endocrine neoplasia type 2A (MEN 2A) has been assigned to chromosome 10, and affected gene carriers can be identified before the development of associated malignancy in some informative families. We applied these advances in gene mapping to clinical screening for possible pediatric surgery. A family with MEN 2A, consisting of 88 members and their spouses, was studied to test the reliability of the provocation of plasma calcitonin with pentagastrin and the possibility of DNA diagnosis of mutated gene carriers with DNA probes closely linked to the MEN2A gene including RBP3 and FNRB genes. Nineteen of the 88 were diagnosed as MEN 2A carriers. Twelve of them were treated surgically and the others died of medullay thyroid carcinoma (MTC) or pheochromocytoma. A strikingly sensitive response of calcitonin was observed in ALL those with MTC. The genotypes cosegregating with the abnormal allele at MEN2A in this family could be deduced from clinically established affected members. The early detection of gene carriers allows us to concentrate our screening efforts on children at high risk and to release non gene carriers from repeated unnecessary testing. MEN2A is one of the first cancer syndromes for which DNA screening permits early detection of members at high risk.

Familial medullary thyroid carcinoma is related to germ-line mutations in the RET oncogene, mainly in cysteine codon 10 or 11, whereas noncysteine mutations in codons 13-15 are rare. We now report a new missense point mutation in exon 8 of the RET gene (1597G-->T) corresponding to a Gly(533)Cys substitution in the cysteine-rich domain of RET protein in 76 patients from a 6-generation Brazilianfamily with 229 subjects, with ascendants from Spain. It is likely that the mutation causes familial medullary thyroid carcinoma (FMTC), because no other mutation was found in RET, the mutation cosegregates with medullary thyroid carcinoma (MTC) or C cell hyperplasia (CCH) in patients subjected to surgery, and family members without the mutation are clinically unaffected. The histological analysis of 35 cases submitted to thyroidectomy revealed that 21 patients had MTC after the age of 40 yr and 8 before the age of 40 yr, 4 presented MTC or CCH before the age of 18 yr, 2 died due to MTC at the age of 53 and 60 yr, and CCH was found in a 5-yr-old child, suggesting a clinical heterogeneity. To improve the diagnosis of FMTC, analysis of exon 8 of RET should be considered in families with no identified classical RET mutations.

Neuroblastoma (NB) is a childhood cancer that arises in the adrenal gland and often shows differentiated neuronal and glial elements. The RET receptor signal pathway is functional in most NB, while loss of nerve growth factor (NGF) receptor (trkA) gene expression correlates with an aggressive phenotype. Thus, we hypothesized that the RET and TRKA signal pathways collaborate to instruct NB differentiation, reminiscent of normal neuronal maturation. Here, we demonstratethat activation of the RET receptor by glial cell line-derived neurotrophic factor (GDNF) increases expression of the RET receptor complex in a panel of malignant human NB cell lines, indicative of a positive feedback mechanism. GDNFalso induces growth cessation concomitant with an arrest of cells in the G(0)/G(1) phase of the cell cycle. Furthermore, GDNF synergizes with ciliary neurotrophic factor (CNTF) to enhance TRKA receptor expression, thereby strengthening the NGF-mediated differentiation signal. Differentiated NB cells downregulate expression of the amplified N-myc gene, concurrent with the arrest of cell proliferation, while expressing neuron-specific markers (i.e., SCG10). Interestingly, maintenance of differentiated NB cells in culture is independent of the trophic activity of GDNF, but depends on TRKA signaling, thereby re-enacting the differentiation of normal sympathoadrenal (SA) progenitor cells.

We report a 12 year old boy with an isolated medullary thyroid carcinoma (MTC). A mutation analysis of the RET-proto-oncogene in this boy showed an in frame insertion-deletion mutation (insTTCTdelG) at codon 666 of the RET proto-oncogene. This RET mutation has not been reported previously. The boy's mother and his 82-year-old maternal grandfather showed the same mutation. None of the two ever showed symptoms of MTC. The mother underwent a preventive total thyroidectomy and pathological examination showed C-cell hyperplasia and early MTC. Further genetic analysis showed that the boy inherited a well-known coding polymorphism in exon 11 (G691S) from his father. Therefore the boy is a compound heterozygote for theinsertion-deletion mutation at codon 666 and the G691S polymorphism in the RET gene. We hypothesize that the insTTCTdelG mutation at codon 666 is associated with low penetrance for MTC and that the young age of MTC in the reported child results most likely from the additive effects of both mutations (insTTCTdelG andG691S).

Recurrent chromosomal rearrangements are common in cancer cells and may be influenced by nonrandom positioning of recombination-prone genetic loci in the nucleus. However, the mechanism responsible for spatial proximity of specific loci is unknown. In this study, we use an 18 Mb region on 10q11.2-21 containing the RET gene and its recombination partners, the H4 and NCOA4 (ELE1) genes, as amodel chromosomal region frequently involved in RET/PTC rearrangements in thyroid cancer. RET/PTC is particularly common in tumors from children exposed to ionizing radiation. Using fluorescence in situ hybridization and three-dimensional microscopy, the locations of five different loci in this region were mapped in interphase nuclei of normal human thyroid cells. We show that RETand NCOA4 are much closer to each other than expected based on their genomic separation. Modeling of chromosome folding in this region suggests the presence of chromosome coiling with coils of approximately 8 Mb in length, which positions the RET gene close to both, the NCOA4 and H4, loci. There was no significant variation in gene proximity between adult and pediatric thyroid cells. This study provides evidence for large-scale chromosome folding of the 10q11.2-21 region that offers a structural basis for nonrandom positioning and spatial proximity of potentially recombinogenic intrachromosomal loci.

OBJECTIVE: Evaluation of treatment of children who are proven carriers of a multiple endocrine neoplasia type 2 (MEN 2)-associated rearranged during transfection (RET) gene mutation. DESIGN: Retrospective case study and review ofthe literature. METHOD: Between 1976 and 2005, 6 boys and 14 girls with a provenRET mutation or biochemical indication of MEN 2 had thyroid surgery at the University Medical Center, Groningen, The Netherlands. The median age was 10 years (range: 0-08). Preoperative assessment, surgical procedure, pathological findings, postoperative complications and treatment results were studied and compared with data from the literature. RESULTS: ALL 20 children underwent totalthyroidectomy. In 17 children with preoperatively abnormal basal or stimulated calcitonin levels, total thyroidectomy was combined with tracheo-oesophageal exploration (n = 6) or central compartment dissection (n = 11). C-cell hyperplasia was found in 19 cases (95%) and medullary thyroid carcinoma in 14 (70%; aged 3-18 years). Lymph-node metastases were found in 3 children (15%), ALL over the age of 10. They underwent additional selective lateral neck dissection,unilateral in 2 cases and bilateral in 1. Two children developed hypoparathyroidism postoperatively, no recurrent laryngeal-nerve palsy was observed. ALL patients are clinically free of disease after a median follow-up of 9 years (range: 0.6-27). The patients with node metastases still have biochemical evidence of disease. The literature indicates that the progression of the malignant transformation to medullary thyroid carcinoma is connected to the typeof RET-mutation. The treatment plan depends on the type of mutation. CONCLUSION:Medullary thyroid cancer occurs at a very young age in carriers ofgermline RET mutations. In patients with high-risk mutations prophylactic thyroidectomy is likely to be recommended before the child reaches the age of 2. Elective centrallymph-node dissection can be omitted in this instance. After this age, however, the risk of lymph-node metastases increases and, for cases with increased basal or stimulated calcitonin levels, total thyroidectomy with central compartment dissection is indicated.

Multiple endocrine neoplasia (MEN) type 2B is a rare hereditary disorder characterized by medullary thyroid carcinoma, pheochromocytoma, and neuroma. Early signs of MEN 2B are usually neuroma, gastrointestinal problems, and medullary thyroid carcinoma. Noncardiogenic pulmonary edema is rare as a presenting symptom. We report a 31-year-old male who was admitted to our hospital because of noncardiogenic pulmonary edema. He was 168 cm in height, weighed 55 kg, and had an arm span of 166 cm. No marfanoid habitus was evident, but thickened lips and tongue neuroma were present. Chronic constipation had been present since childhood, and the patient had a two-year history of untreated hypertension. Noncardiogenic pulmonary edema and toxic megacolon were noted, andabdominal computed tomography revealed bilateral adrenal tumors. Ultrasonographyof the thyroid showed two mass lesions. Intubation and mechanical ventilation were performed because of severe hypoxemia. Endocrinological examinations showedhigh levels of serum and urinary fractionated catecholamines, serum calcitonin, serum carcinoembryonic antigen, and serum intact parathyroid hormone. It was suggested that the high level of catecholamine from pheochromocytoma had caused the pulmonary edema. RET gene analysis showed a codon 918 mutation in exon 16 resulting in an ATG (methionine) to ACG (threonine) substitution, but analysis of the patient's parents showed the wild type. Therefore, the patient was diagnosedas having de novo MEN 2B. He underwent laparoscopic bilateral adrenectomy and total thyroidectomy. However, the values of serum calcitonin and CEA did not decrease to the normal ranges. Patients with early-stage MEN 2B have distinct characteristics that can aid early detection of the disease, thus possibly allowing them to be saved.

Multiple endocrine neoplasia (MEN) type 2B is a rare hereditary disorder characterized by medullary thyroid carcinoma, pheochromocytoma, and neuroma. Early signs of MEN 2B are usually neuroma, gastrointestinal problems, and medullary thyroid carcinoma. Noncardiogenic pulmonary edema is rare as a presenting symptom. We report a 31-year-old male who was admitted to our hospital because of noncardiogenic pulmonary edema. He was 168 cm in height, weighed 55 kg, and had an arm span of 166 cm. No marfanoid habitus was evident, but thickened lips and tongue neuroma were present. Chronic constipation had been present since childhood, and the patient had a two-year history of untreated hypertension. Noncardiogenic pulmonary edema and toxic megacolon were noted, andabdominal computed tomography revealed bilateral adrenal tumors. Ultrasonographyof the thyroid showed two mass lesions. Intubation and mechanical ventilation were performed because of severe hypoxemia. Endocrinological examinations showedhigh levels of serum and urinary fractionated catecholamines, serum calcitonin, serum carcinoembryonic antigen, and serum intact parathyroid hormone. It was suggested that the high level of catecholamine from pheochromocytoma had caused the pulmonary edema. RET gene analysis showed a codon 918 mutation in exon 16 resulting in an ATG (methionine) to ACG (threonine) substitution, but analysis of the patient's parents showed the wild type. Therefore, the patient was diagnosedas having de novo MEN 2B. He underwent laparoscopic bilateral adrenectomy and total thyroidectomy. However, the values of serum calcitonin and CEA did not decrease to the normal ranges. Patients with early-stage MEN 2B have distinct characteristics that can aid early detection of the disease, thus possibly allowing them to be saved.

Multiple endocrine neoplasia (MEN) type 2B is a rare hereditary disorder characterized by medullary thyroid carcinoma, pheochromocytoma, and neuroma. Early signs of MEN 2B are usually neuroma, gastrointestinal problems, and medullary thyroid carcinoma. Noncardiogenic pulmonary edema is rare as a presenting symptom. We report a 31-year-old male who was admitted to our hospital because of noncardiogenic pulmonary edema. He was 168 cm in height, weighed 55 kg, and had an arm span of 166 cm. No marfanoid habitus was evident, but thickened lips and tongue neuroma were present. Chronic constipation had been present since childhood, and the patient had a two-year history of untreated hypertension. Noncardiogenic pulmonary edema and toxic megacolon were noted, andabdominal computed tomography revealed bilateral adrenal tumors. Ultrasonographyof the thyroid showed two mass lesions. Intubation and mechanical ventilation were performed because of severe hypoxemia. Endocrinological examinations showedhigh levels of serum and urinary fractionated catecholamines, serum calcitonin, serum carcinoembryonic antigen, and serum intact parathyroid hormone. It was suggested that the high level of catecholamine from pheochromocytoma had caused the pulmonary edema. RET gene analysis showed a codon 918 mutation in exon 16 resulting in an ATG (methionine) to ACG (threonine) substitution, but analysis of the patient's parents showed the wild type. Therefore, the patient was diagnosedas having de novo MEN 2B. He underwent laparoscopic bilateral adrenectomy and total thyroidectomy. However, the values of serum calcitonin and CEA did not decrease to the normal ranges. Patients with early-stage MEN 2B have distinct characteristics that can aid early detection of the disease, thus possibly allowing them to be saved.

Pheochromocytomas (PCCs) are rare catecholamine-producing tumors of the adrenal gland which may also occur elsewhere in the abdomen and are then called paragangliomas. A proportion of PCCs occurs in hereditary cancer syndromes, including multiple endocrine neoplasia Type 2 (MEN2), caused by mutations in theRET proto-oncogene, von Hippel-Lindau (VHL) disease, caused by VHL gene abnormalities, and the pheochromocytoma-paraganglioma (PCC-PGL) syndrome, causedby mutations in SDHB and SDHD. Since a proportion of PCCs occurs in children we hypothesized that germline mutations in RET, VHL, succinate dehydrogenase subunit B (SDHB), and subunit D (SDHD) occur more frequently in the pediatric age range.From our single-institution collection of PCCs, we have selected 10 cases that occurred in individuals up to 18 years of age at diagnosis. In these, we have performed mutation analysis on normal and tumor tissues for exons 10, 11, and 16of RET and for the entire coding sequence of VHL, SDHB, and SDHD. The 10 patients include 7 boys and 3 girls, with an average age of 15.5 years (range 9-18 years). Two patients had germline RET exon 11 mutations (C634R) and 1 patient had an R64P germline mutation in the VHL gene. In the remaining 7 patients there was one patient from a family fulfilling the clinical criteria for VHL disease. ALL tumors were benign (average follow-up: 12 years) and were located in the adrenal. From our findings we conclude that (a) a large proportion (40%) of pediatric PCCpatients is diagnosed in the context of inherited cancer syndromes, and (b) candidate gene analysis appears to be indicated to detect germline mutations.

BACKGROUND: Multiple endocrine neoplasia 2B (MEN2B) has a classic childhood phenotypic presentation characterized by mucosal neuromas and marfanoid habitus.However, the diagnosis of MEN2B is often delayed beyond childhood, at which timemedullary thyroid carcinoma (MTC) may be regionally advanced or metastatic. We examined the extent of this delay and its impact on the treatment of MTC. METHODS: Patients in the MEN database were retrospectively analyzed to determinethe age at first presentation for a MEN2B-related complaint and the subsequent time to correct diagnosis. Operative and pathology reports were reviewed to determine the extent of thyroidectomy and cervical lymphadenectomy during the initial and subsequent neck operations. RESULTS: We identified 22 patients with MEN2B, 20 were de novo cases and a M918T RET gene mutation was confirmed in 18 of the 22 patients. Median age at diagnosis of MTC was 13 years (range 6-25 years).The median delay in diagnosis was 26 months (range 0-18 years). Persistent local-regional MTC was present following the initial cervical operation in 12 of22 patients (55%); including 4 of 13 with MEN2B diagnosed prior to initial surgery and 8 of 9 with MEN2B diagnosed after initial surgery. CONCLUSIONS: Mostpatients displayed phenotypic characteristics of MEN2B long before the correct diagnosis was made. Half of the patients failed to undergo complete resection ofMTC at their initial thyroid surgery. Early recognition of the MEN2B phenotype with a thoughtful approach to preoperative staging and surgery will maximize control of MTC and minimize the need for reoperation.

PURPOSE: To emphasize the importance of genetic studies in family members and early prophylactic thyroidectomy in oncogene mutation carriers in the managementof familiar medullary thyroid carcinoma. METHODS: A retrospective review of families with familiar medullary thyroid carcinoma treated at our center in the last 7 years was performed. We identified a total of 7 families who has isolatedprevalences with thyroid malignancies. Forty members of the 7 families were screened for gene RET mutations. Prophylactic total thyroidectomy was performed in every RET mutation gene carriers. RESULTS: In ALL families the index case were patients with medullary thyroid carcinoma presenting at a mean age of 37.25 years (range 23-42). The RET oncogen mutation was in codon 634 in exon 11 (multiple endocrine neoplasia type 2A) in ALL these patients. Fourteen gene carriers were identified with a mean age of 20 years (range 7-37), eleven of whom had medullary thyroid carcinoma at the time of surgery. Five of the gene carriers were children, with a mean age of 11 years (range 7-16), four of whom had microcarcinoma and one had metastatic carcinoma at the time of surgery. After surgery no hypoparathyroidism or recurrent nerve paralysis were documented. No pediatric patient has presented with phaeochromocytoma or hypoparathyroidism to date Four of the five children have normal calcitonin levels (< 2 pg/ml) and they are free of disease. The one who presented metastatic carcinoma has recurrent disease and is awaiting surgical treatment. CONCLUSIONS: Genetic studies of family members related to patients with familiar medullary thyroid carcinoma andRET mutations is indispensable. The RET mutation in codon 634 exon 11 was found to be the most frequent association. Prophylactic thyroidectomy is the only curative treatment and has minimal complications when performed by expert surgeons. Early thyroidectomy is recommended since distant metastatic spread canoccur at early age.

A major early event in papillary thyroid carcinogenesis is constitutive activation of the mitogen-activated protein kinase signaling pathway caused by alterations of a single gene, typically rearrangements of the RET and NTRK1 genes or point mutations in the BRAF and RAS genes. In childhood papillary thyroid cancer, regardless of history of radiation exposure, RET/PTC rearrangements are a major event. Conversely, in adult-onset papillary thyroid cancer among the general population, the most common molecular event is BRAF(V600E) point mutation, not RET/PTC rearrangements. To clarify which gene alteration, chromosome aberration, or point mutation preferentially occurs in radiation-associated adult-onset papillary thyroid cancer, we have performed molecular analyses on RET/PTC rearrangements and BRAF(V600E) mutation in 71 papillary thyroid cancer cases among atomic bomb survivors (including 21 cases not exposed to atomic bomb radiation), in relation to radiation dose as well as time elapsed since atomic bomb radiation exposure. RET/PTC rearrangements showedsignificantly increased frequency with increased radiation dose (P(trend) = 0.002). In contrast, BRAF(V600E) mutation was less frequent in cases exposed to higher radiation dose (P(trend) < 0.001). Papillary thyroid cancer subjects harboring RET/PTC rearrangements developed this cancer earlier than did cases with BRAF(V600E) mutation (P = 0.03). These findings were confirmed by multivariate logistic regression analysis. These results suggest that RET/PTC rearrangements play an important role in radiation-associated thyroid carcinogenesis.

Risk factors for thyroid cancer remain largely unknown except for ionizing radiation exposure during childhood and a history of benign thyroid nodules. Because thyroid nodules are more common than thyroid cancers and are associated with thyroid cancer risk, we evaluated several polymorphisms potentially relevant to thyroid tumors and assessed interaction with ionizing radiation exposure to the thyroid gland. Thyroid nodules were detected in 1998 by ultrasound screeningof 2997 persons who lived near the Semipalatinsk nuclear test site in Kazakhstanwhen they were children (1949-1962). Cases with thyroid nodules (n = 907) were frequency matched (1:1) to those without nodules by ethnicity (Kazakh or Russian), gender and age at screening. Thyroid gland radiation doses were estimated from fallout deposition patterns, residence history and diet. We analyzed 23 polymorphisms in 13 genes and assessed interaction with ionizing radiation exposure using likelihood ratio tests (LRT). Elevated thyroid nodule risks were associated with the minor alleles of RET S836S (rs1800862, P = 0.03) and GFRA1 -193C>G (rs not assigned, P = 0.05) and decreased risk with XRCC1 R194W (rs1799782, P trend = 0.03) and TGFB1 T263I (rs1800472, P = 0.009). Similar patterns of association were observed for a small number of papillary thyroid cancers (n = 25). Ionizing radiation exposure to the thyroid gland was associated with significantly increased risk of thyroid nodules (age and gender adjusted excess odds ratio/Gy = 0.30, 95% CI 0.05-0.56), with evidence for interaction bygenotype found for XRCC1 R194W (LRT P value = 0.02). Polymorphisms in RET signaling, DNA repair and proliferation genes may be related to risk of thyroid nodules, consistent with some previous reports on thyroid cancer. Borderline support for gene-radiation interaction was found for a variant in XRCC1, a key base excision repair protein. Other pathways such as genes in double-strand break repair, apoptosis and genes related to proliferation should also be pursued.

BACKGROUND: The hereditary form of medullary thyroid carcinoma may occur isolated as a familial medullary thyroid carcinoma (FMTC) or as part of Multiple Endocrine Neoplasia 2A (MEN2A) and 2B (MEN2B). MEN2B is a rare syndrome, its phenotype mayusually, but not always, be noted by the physician. In the infant none of the MEN2B characteristics are present, except by early gastrointestinal dysfunction caused by intestinal neuromas. When available, genetic analysis confirms the diagnosis and guides pre-operative evaluation and extent of surgery. Here we report four cases of MEN2B in which the late diagnosis had a significant impact in clinical evolution and, potentially, in overall survival. CASE REPORT: We report four cases, 2 men and 2 women, with differences in their phenotypes and with a late diagnosis. The first case has a history of severe gastrointestinal obstruction requiring a surgery intervention two days after his birth. The second told had nodules in the oral mucosa and constipation since childhood. The third case referred a history of constipation from birth until 5 months of life. The fourth has had a history of chronic constipation since childhood. DISCUSSION: New concepts have emerged since the RET oncogene was identified in 1993 as the responsible gene for hereditary medullary thyroid carcinoma. The majority of MEN2B individuals have M918T mutation in the exon 16 of RET, with a few cases having a mutation A883F or the association of V804M with E805K, Y806C or S904C mutations. The consensus classifies the RET mutation in codon 918 as of highest risk and recommends total thyroidectomy and central lymph node dissection until 6 months after birth. A fast and precise diagnosis is essential to reach these goals. The identification of early manifestations such as intestinal ganglioneuromatosis and oral mucosal neuromas should prompt the physician to initiate an investigation for multiple endocrine neoplasia type 2B. CONCLUSION: The diagnosis of MEN2B is very important to allow appropriate investigation of associated diseases and to allow counseling and appropriate screening of relatives for a RET mutation. Even patients with MEN2B, which often have typicalphysical features, may not be properly recognized and be followed as a sporadic case. Based on this, ALL suspicious cases of multiple endocrine neoplasia shouldundergo a molecular genetic test.

Structural chromosome aberrations are known hallmarks of many solid tumors. In the papillary form of thyroid cancer (PTC), for example, activation of the receptor tyrosine kinase (RTK) genes, ret or the neurotrophic tyrosine kinase receptor type I (NTRK1) by intra- or interchromosomal rearrangements have been suggested as a cause of the disease. The 1986 accident at the nuclear power plant in Chernobyl, Ukraine, led to the uncontrolled release of high levels of radioisotopes. Ten years later, the incidence of childhood papillary thyroid cancer (chPTC) near Chernobyl had risen by two orders of magnitude. tumors removed from some of these patients showed aberrant expression of the ret RTK gene due to a ret/PTC1 or ret/PTC3 rearrangement involving chromosome 10. However, many cultured chPTC cells show a normal G-banded karyotype and no ret rearrangement. We hypothesize that the "ret-negative" tumors inappropriately express a different oncogene or have lost function of a tumor suppressor as a result of chromosomal rearrangements, and decided to apply molecular and cytogenetic methods to search for potentially oncogenic chromosomal rearrangements in Chernobyl chPTC cases. Knowledge of the kind of genetic alterations may facilitate the early detection and staging of chPTC as well as provide guidance for therapeutic intervention.

BTI - GeneReviews#. Multiple endocrine neoplasia type 2 (MEN 2) is classified into three subtypes: MEN 2A, FMTC (familial medullary thyroid carcinoma), and MEN 2B. ALL three subtypes involve high risk for development of medullary carcinoma of the thyroid(MTC); MEN 2A and MEN 2B have an increased risk for pheochromocytoma; MEN 2A hasan increased risk for parathyroid adenoma or hyperplasia. Additional features inMEN 2B include mucosal neuromas of the lips and tongue, distinctive facies with enlarged lips, ganglioneuromatosis of the gastrointestinal tract, and an asthenic 'marfanoid' body habitus. MTC typically occurs in early childhood in MEN 2B, early adulthood in MEN 2A, and middle age in FMTC. RET is the only gene in whichmutations are known to cause MEN type 2. Molecular genetic testing of RET identifies disease-causing mutations in 98% of individuals with MEN 2A, more than 98% of individuals with MEN 2B, and in about 95% of families with FMTC. Treatment of manifestations: Treatment for MTC is surgical removal of the thyroid gland and lymph node dissection. Pheochromocytomas detected by biochemical testing and radionuclide imaging are removed by adrenalectomy. Primary hyperparathyroidism is treated with surgery to remove one or more parathyroid glands, or more rarely, medications to reduce parathyroid hormone secretion. Prevention of primary manifestations: Prophylactic thyroidectomy for individuals with an identified germline RET mutation. Prevention of secondary complications: Prior to any surgery in an individual with MEN 2A or MEN 2B, the presence of a functioning pheochromocytoma should be excluded by appropriate biochemical screening. Surveillance: Annual measurement of serum calcitonin concentration to detect residual or recurrent MTC after thyroidectomy, even if thyroidectomy was performed prior to biochemical evidence of disease. Monitoring for possible hypoparathyroidism in ALL those who have undergone thyroidectomy and parathyroidautotransplantation. Annual biochemical screening for those with RET mutations whose initial screening results are negative for pheochromocytoma. Agents/circumstances to avoid: Dopamine D2 receptor antagonists and beta-adrenergic receptor antagonists present a high risk for adverse reactions in individuals with pheochromocytoma. Evaluation of relatives at risk: RET molecular genetic testing should be offered to ALL at-risk members of kindreds in which a germline RET mutation has been identified. Pregnancy management: Women with MEN 2 should be screened for pheochromocytoma prior to a planned pregnancy, or as early as possible during an unplanned pregnancy. ALL MEN 2 subtypes are inherited in an autosomal dominant manner. The probability of a de novo gene mutation is 5% or less in index cases with MEN 2A and 50% in index cases with MEN 2B. Offspring ofaffected individuals have a 50% chance of inheriting the mutant gene. Prenatal testing is possible.#CI- Copyright (c) 1993-2013, University of Washington, Seattle. ALL rights reserved.#FED - Pagon, Roberta A#ED- Pagon RA#FED - Adam, Margaret P#ED- Adam MP#FED - Bird, Thomas D#ED- Bird TD#FED - Dolan, Cynthia R#ED- Dolan CR#FED - Fong, Chin-To#ED- Fong CT#FED - Stephens, Karen#ED- Stephens K#FAU - Moline, Jessica

PURPOSE: Hereditary medullary thyroid carcinoma (MTC) therapy is surgical resection. Because the genetic screening was available, the early diagnosis of the disease has been possible. The purpose of this study was to evaluate the role of the genetic test in the management of these children and to draw some information about the surgical timing. METHODS: Thirteen patients underwent total thyroidectomy at our institute between 1995 and 2007. Seven patients underwent acurative thyroidectomy, and 6 patients underwent a prophylactic thyroidectomy. Two patients were operated with a minimally invasive video-assisted technique. We studied the following parameters: age, risk level associated to the RET gene mutations, aim of surgery (curative or prophylactic), tumor histopathologic features, lymph node involvement, and distal metastases. RESULTS: We found a statistical association between cancer maximum diameter and some parameters analyzed: age of patients, aim of surgery, single or multifocal MTC, and number of organs involved by distal metastases. cancer diameter at the moment of diagnosis seems to increase according to the aggressiveness of RET gene mutationfound. CONCLUSIONS: The best strategy to cure MTC is to prevent it. Genetic screening could be a fundamental tool in the management of multiple endocrine neoplasm type 2 children. An improvement of scientific knowledge regarding RET gene alterations and an early and appropriate use of genetic tests could allow abetter understanding of the correct surgical timing and a wider use of less aggressive surgical procedures.#CI- Copyright 2010. Published by Elsevier Inc.

INTRODUCTION: MEN2A is an autossomal dominant cancer syndrome characterised by the presence of medullary thyroid cancer, pheochromocytoma and primary hyperparathyroidism. Germline mutations of the RET protooncogene constitute the molecular defect and can be identified in affected individuals. Genetic screening of family members at risk allows early diagnosis and preventive measures before the appearance of the disease. We present a family with several members affectedwith MEN2A, their molecular characterisation and the clinical implications of genetic testing. POPULATION AND METHODS: We studied 18 members distributed amongthree generations of a family of which four members were clinically affected with MEN2A and cutaneous lichen amyloidosis. RET gene mutations were screened for in affected individuals and their offspring by PCR-RFLP techniques. RESULTS: Genetic testing revealed a point mutation at codon 634 (TGC>TGG), in the heterozygous state, in ALL affected individuals. The same mutation was also found in a five years old asymptomatic child which after total thyroidectomy showed to have multifocal medullary thyroid carcinoma. DISCUSSION: Genetic screening is the most suitable method for pre-symptomatic diagnosis of MEN2A allowing an efficient andearly identification of individuals who will later develop the disease. These can be monitored more closely and be submitted to a prophylactic thyroidectomy before the appearance of medullary thyroid carcinoma. The ideal moment for this intervention is still under discussion although the results of this study suggest that it should be undertaken before the age of five.

Multiple endocrine neoplasia type 1 (MEN-1) is an autosomal-dominant hereditary disease characterized by the occurrence of tumors of the parathyroids, duodenum and/or pancreas, and anterior pituitary. The syndrome is caused by germline mutations of the MEN1 tumor suppressor gene. The identification of the causativemutations is of paramount importance for the long-term management of affected individuals and their relatives. Multiple endocrine neoplasia type 2 (MEN2) is less frequent than MEN1 and represents a cancer syndrome caused by autosomal-dominant inherited mutations of the RET proto-oncogene, and displays agenotype-phenotype correlation of remarkable clinical relevance. Major components of MEN-2 comprise medullary thyroid carcinoma (MTC), pheochromocytoma, and primary hyperparathyroidism. Since 25-30% of patients with MTC display a hereditary background, genetic testing is indicated once MTC is diagnosed. Occurrence of MTC can be avoided by prophylactic thyroidectomy in early childhood in gene carriers. Early diagnosis and therapy of simultaneous pheochromocytoma avoids the development of complications caused by acute or chronic hypertension.

BACKGROUND: The clinical association of multiple endocrine neoplasia type 2A (MEN 2A) and Hirschsprung's disease (HD), although rare, has been previously observed. Recently, germline mutations in the RET proto-oncogene, a transmembrane receptorwith tyrosine kinase activity, have been detected in patients with familial HD. RET is also the predisposition gene for the inherited cancer syndrome MEN 2A. METHODS: We describe a DNA sequence variation within the coding region of RET intwo large unrelated kindreds with MEN 2A (with 83 and 42 persons affected) in which HD cosegregated with MEN 2A in seven patients. mutational analysis was performed with a highly sensitive polymerase chain reaction-based denaturing gradient gel electrophoresis technique followed by direct sequencing of mutants.RESULTS: Genetic analysis by denaturing gradient gel electrophoresis detected mutant bands in RET exon 10 in patients with MEN 2A from both kindreds. Direct DNA sequencing of mutants revealed a thymine-to-adenine base change in codon 618, resulting in a cysteine-to-serine substitution. The identical mutation was present in ALL seven children with HD. Of these children five underwent thyroidectomy for C-cell abnormalities; one 3-year-old child is awaiting thyroidsurgery, and the remaining patient died at age of 12 weeks. CONCLUSIONS: The RETcodon 618 Ser mutation could predispose patients with MEN 2A to HD. RET may assume a critical role in embryologic enteric nerve migration and tumorigenesis of cells from neural crest lineage.

The authors report the case of a female infant who was referred at the age of 18months for a left latero-cervical mass. This child belongs to a family with a history of multiple endocrine neoplasia (MEN) type 2a (10 persons in 4 generations had medullary thyroid carcinoma and/or pheochromocytoma). Surgery was performed with complete excision of an encapsulated tumor and pathological examination reported a typical ganglioneuroblastoma. No amplification of N-myc oncogene was observed. The probability of the child carrying a MEN-2a gene is estimated 2 to 4%, by DNA analysis. The patient has received no further treatment and is still free of disease 4 years later. The diagnostic problems of this tumor after basic tests were between neuroblastoma and medullary thyroid carcinoma. The link between neuroblastoma and MEN-2a syndrome is discussed because both diseases belong to the group of neural crest tumors.

Activation of the RET tyrosine kinase domain occurs in a proportion of thyroid papillary carcinomas. Three chromosomal rearrangements have been described, of which PTC1 is the commonest. Wide differences (2.5-25%) in frequency of PTC1 in different populations have been reported; it is not clear whether these are due to environmental factors, racial differences or technical reasons. We have developed a simple and rapid reverse transcriptase nested polymerase chain reaction (RT-nPCR) method enabling the detection of gene expression from single 5 microns sections of formalin-fixed paraffin wax-embedded archival material. We have applied this approach to detect expression of the RET tyrosine kinase domain, allowing identification of RET activation resulting from any rearrangement, whether characterised or not, or from overexpression. A retrospective study was performed on 22 adult and 21 childhood papillary carcinomas. Thirteen of 22 (59%) adult and 10 of 21 (48%) childhood carcinomas showed evidence of RET activation, demonstrating a major role for the RET oncogene in UK thyroid papillary carcinogenesis. This study also shows a similarfrequency of RET activation in both children and adults. The use of a technique that allows reliable amplification of RNA from archival material, using primers chosen in different exons so that amplified products are readily distinguished from genomic DNA, will allow correlation of translocations and chromosomal rearrangements with a variety of specific tumour types.

Ionizing radiation is a well-known risk factor of cancer development, but the mechanism of radiation induced carcinogenesis is not clear. Chromosomal rearrangements induced by radiation most likely are one of the principal geneticalterations resulting in malignant transformation. The chimeric BCR-ABL associated with chronic myelogenous leukemia (CML) and H4-RET oncogenes associated with thyroid papillary carcinoma are the result of a translocation and inversion, respectively. In vitro studies showed these genes were induced by high-doses of X-irradiation in cell lines. Studies also show that therapeutic external X-ray doses as high as 60 Gy for treatment of various childhood cancersincluding Hodgkin's disease significantly increase the risk of thyroid cancer. Therefore, we examined the induction and persistence of these chimeric genes in human thyroid tissues transplanted in scid mice after 50 Gy exposure as a function of time for 2 months to elucidate the early events of thyroid carcinogenesis. The H4-RET genes were detected on day 2 and throughout the 2 month period. On the other hand, BCR-ABL genes were detected on day 2 and were undetectable subsequently. These results suggest that ionizing radiation causes various oncogene activations, but cells with only specific gene alteration uniquely associated with thyroid carcinogenesis are selectively retained demonstrating one of the early events in the beginnings of radiation carcinogenesis in human thyroid tissues.

INTRODUCTION: Medullary carcinoma of the thyroid (MTC) is a rare tumour which occurs in both sporadic and hereditary forms. mutations of the RET proto-oncogene have been identified in hereditary forms. The aim of our study was to confirm orexclude familial disease by examining for germline mutations in the RET proto-oncogene in patients with medullary thyroid carcinoma. METHODS: Nine patients with medullary thyroid carcinoma and 4 of their children were studied. Peripheral blood was used to examine for mutations in the RET proto-oncogene. When this was not available, archival thyroid tissue was used. RESULTS: Seven patients had clinically sporadic tumours confirmed by mutational analysis of RET. Four children were at risk of being carriers of a mutated gene, as their fathershad histologically proven MTC and had tested positive for the mutation at codon 618 on exon 10 of the RET proto-oncogene. Three of these children carried the 618 mutation. To date, 2 have had a prophylactic thyroidectomy, the pathology of which revealed C-cell hyperplasia. One child had familial disease excluded by mutational analysis. One patient had a clinical diagnosis of MEN2B confirmed by detection of the 918 mutation on exon 16 of the RET proto-oncogene. CONCLUSIONS:RET proto-oncogene analysis is a reliable method of differentiating familial from sporadic MTC. mutational information determines which family members of affectedkindreds are at risk of developing the disease and can be used to affect clinical management.