Predictive DNA testing for multiple endocrine neoplasia 2: a therapeutic challenge of prophylactic thyroidectomy in very young children

Temporal Trends in the Presentation, Treatment, and Outcome of Medullary Thyroid Carcinoma: An Israeli Multicenter Study

BACKGROUND

The widespread use of neck sonography in recent years has led to a dramatic increase in the detection of thyroid cancer, accompanied by changes in the clinicopathologic features of the disease. However, small papillary carcinomas account for the bulk of this increase, while little is known about temporal changes in medullary thyroid carcinoma (MTC). The aim of this study was to evaluate trends in the presentation, treatment, and outcome of MTC.

METHODS

Patients treated for MTC at four medical centers in Israel were divided into three groups by year of diagnosis: 19811995 (period A), 1996-2005 (period B), and 2006-2016 (period C). Clinicopathologic and survival data were collected retrospectively from the medical files and compared between the groups.

RESULTS

The cohort included 182 patients (54.9% female) with a mean age of 49.2 ± 18.7 years: 43 (23.6%) diagnosed in period A, 54 (29.7%) in period B, and 85 (46.7%) in period C. No significant differences were found between the groups in primary tumor size (25.7 ± 18.9 mm, 26.6 ± 18 mm, and 23.7 ± 17.6 mm, respectively), proportion of micro-MTC (30.8%, 20.0%, and 25.3%, respectively), or TNM staging. Age at diagnosis significantly increased over time (38.7 ± 17.2 years, 51.7 ± 18.4 years, and 53.7 ± 17.7 years, respectively; p < 0.001), and the rate of familial MTC significantly decreased (41.9%, 14.8%, and 8.2%, respectively; p = 0.002). Although the implementation of cervical lymph node dissection increased (62.1%, 78.4%, and 85%, respectively; p = 0.01), detection of metastatic lymph nodes decreased from 88.9% in period A to 65.0% in periods B and C (p = 0.06). There was no difference between the groups in disease-specific survival or disease-free state at one year from diagnosis (37.5%, 43.1%, and 50%, respectively) and last follow-up (27%, 41.2%, and 48%, respectively). Similar findings on MTC presentation and outcomes were obtained when only patients with non-familial MTC were analyzed.

CONCLUSIONS

Unlike differentiated thyroid cancer, most of the presenting features of MTC have not changed over time. The most significant temporal change is a decreased rate of familial MTC. Despite more extensive surgery and the use of new treatment modalities in recent years, significant improvement in disease-related outcomes were not found.

Multiple endocrine neoplasias type 2B and RET proto-oncogene

Multiple Endocrine Neoplasia type 2B (MEN 2B) is an autosomal dominant complex oncologic neurocristopathy including medullary thyroid carcinoma, pheochromocytoma, gastrointestinal disorders, marphanoid face, and mucosal multiple ganglioneuromas. Medullary thyroid carcinoma is the major cause of mortality in MEN 2B syndrome, and it often appears during the first years of life. RET proto-oncogene germline activating mutations are causative for MEN 2B. The 95% of MEN 2B patients are associated with a point mutation in exon 16 (M918/T). A second point mutation at codon 883 has been found in 2%-3% of MEN 2B cases. RET proto-oncogene is also involved in different neoplastic and not neoplastic neurocristopathies. Other RET mutations cause MEN 2A syndrome, familial medullary thyroid carcinoma, or Hirschsprung's disease. RET gene expression is also involved in Neuroblastoma. The main diagnosis standards are the acetylcholinesterase study of rectal mucosa and the molecular analysis of RET. In our protocol the rectal biopsy is, therefore, the first approach. RET mutation detection offers the possibility to diagnose MEN 2B predisposition at a pre-clinical stage in familial cases, and to perform an early total prophylactic thyroidectomy. The surgical treatment of MEN 2B is total thyroidectomy with cervical limphadenectomy of the central compartment of the neck. When possible, this intervention should be performed with prophylactic aim before 1 year of age in patients with molecular genetic diagnosis. Recent advances into the mechanisms of RET proto-oncogene signaling and pathways of RET signal transduction in the development of MEN 2 and MTC will allow new treatment possibilities.

Medullary thyroid carcinoma: ethical issues for the surgeon

Medullary thyroid cancer is a disease with an established genetic inheritance pattern for which evidence-based guidelines recommend genetic testing and subsequent management of affected patients and their family members. The perceived stigma of genetic testing, coupled with issues involving confidentiality and disclosure, create potential conflict and confusion. In some cases, there is a need for genetic testing and prophylactic surgery in children, augmenting the need for a judicious approach that balances respect for individual autonomy and parental rights with the best interest of the child. We provide an overview of the ethical issues facing surgeons caring for patients with familial medullary thyroid carcinoma, and recommend interventions and resources to assist in decision making in these difficult situations.

Mutational spectrum of multiple endocrine neoplasia type 2 and sporadic medullary thyroid carcinoma in taiwan

BACKGROUND/PURPOSE

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant cancer predisposition syndrome, and > 95% of MEN 2 patients carry rearranged during transfection (RET) protooncogene mutants. We aimed to elucidate the genotype and phenotype relationship of RET proto-oncogene mutations in Taiwanese subjects with medullary thyroid cancer (MTC).

METHODS

We genotyped the MEN-2-associated germ-line mutations by PCR-based sequencing of the RET gene. DNA was extracted from a total of 69 members from eight unrelated families with individuals affected by MTC, and from seven sporadic cases of MTC.

RESULTS

RET mutations were found in four MEN 2A families, all at codon 634 (one with C>R, two with C>F, and one with C>W). One MEN 2A patient carried a de novo mutation at codon 634 (C>R). In two families of MEN 2B, all carried the mutation at codon 918 (M>T). These two cases of MEN 2B were all de novo mutations. One family of familial MTC or unclassified MEN 2 carried the codon 620 (C>F) mutation. Among the seven sporadic cases of MTC, none was found to carry any mutation in hotspot exons. Only two non-synonymous variants (T278N/exon 4 and D489N/exon 7) were found in two cases. However, these two variants were not uncommon in our elderly population.

CONCLUSION

We found that all eight MTC patients with a family history or with the other phenotypes of MEN 2 had RET mutations, whereas no significant RET mutation was found in seven patients with isolated MTC without family history and other endocrine diseases. Molecular scanning of the RET gene in MEN 2 and MTC in Taiwanese patients probably should be limited to exons 10, 11 and 16, initially to be cost-effective.

Multiple endocrine neoplasia type 2

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominantly inherited tumor syndrome subclassified into three distinct syndromes: MEN 2A, MEN 2B and familial medullary thyroid carcinoma. In MEN 2 families, medullary thyroid carcinoma, pheochromocytomas and parathyroid adenomas occur with a variable frequency, also depending on the specific genetic defect involved. In 1993, the responsible MEN2 gene was identified. The genetic defect in these disorders involves the RET proto-oncogene on chromosome 10. The germline RET mutations result in a gain-of-function of the RET protein. Extensive studies on large families revealed that there is a strong genotype-phenotype correlation. In this review, guidelines for early diagnosis, including MEN2 gene mutation analysis, and treatment, including preventive surgery, periodic and clinical monitoring, have been formulated, enabling improvement of life expectancy and quality of life. Identification of the RET protein has also provided new insights into its function, and the specific pathways it effects involved in cell proliferation, migration, differentiation and survival. In the near future, identification of biological tumor markers will enable target-directed intervention and may prevent and/or delay progression of both primary and residual tumor growth.

Medullary thyroid cancer: management guidelines of the American Thyroid Association

BACKGROUND

Inherited and sporadic medullary thyroid cancer (MTC) is an uncommon and challenging malignancy. The American Thyroid association (ATA) chose to create specific MTC Clinical Guidelines that would bring together and update the diverse MTC literature and combine it with evidence-based medicine and the knowledge and experience of a panel of expert clinicians.

METHODS

Relevant articles were identified using a systematic PubMed search and supplemented with additional published materials. Evidence-based recommendations were created and then categorized using criteria adapted from the United States Preventive Services Task Force, Agency for Healthcare Research and Quality.

RESULTS

Clinical topics addressed in this scholarly dialog included: initial diagnosis and therapy of preclinical disease (including RET oncogene testing and the timing of prophylactic thyroidectomy), initial diagnosis and therapy of clinically apparent disease (including preoperative testing and imaging, extent of surgery, and handling of devascularized parathyroid glands), initial evaluation and treatment of postoperative patients (including the role of completion thyroidectomy), management of persistent or recurrent MTC (including the role of tumor marker doubling times, and treatment of patients with distant metastases and hormonally active metastases), long-term follow-up and management (including the frequency of follow-up and imaging), and directions for future research.

CONCLUSIONS

One hundred twenty-two evidence-based recommendations were created to assist in the clinical care of MTC patients and to share what we believe is current, rational, and optimal medical practice.

Medullary thyroid carcinoma in a 2-month-old male with multiple endocrine neoplasia 2B and symptoms of pseudo-Hirschsprung disease: a case report

A 5-week-old male patient was seen for symptoms suggestive of Hirschsprung disease (abdominal distension, failure to thrive, and explosive defecation). Rectum biopsies revealed an intestinal ganglioneuromatosis, which is usually associated with multiple endocrine neoplasia (MEN) syndrome type 2B. The ensuing molecular genetic analysis revealed a M918T mutation of the RET protooncogene, which is associated with early-onset medullary thyroid carcinoma (MTC). Therefore, total thyroidectomy and central lymphadenectomy were performed at the age of 9 weeks. Histology showed a medullary microcarcinoma. This report of MTC occurrence within the first weeks of life underlines the importance of early diagnosis and thyroidectomy in patients with MEN 2B syndrome. Because many patients with MEN 2A and B show gastrointestinal symptoms before the development of MTC, the possibility of MEN 2 should be recognized, and genetic testing for the presence of RET mutations should be included in the explorative diagnosis for megacolon.

The Role of Prophylactic Surgery in Cancer Prevention

BACKGROUND

Since the human genome has been sequenced many mysteries of cell biology have been unravelled, thereby clarifying the pathogenesis of several diseases, particularly cancer. In members of kindreds with certain hereditary diseases, it is now possible early in life to predict with great certainty whether or not a family member has inherited the mutated allele causing the disease. In hereditary malignancies this has been particularly important, because in affected family members there is the possibility of removing the organ destined to develop cancer before malignancy develops or while it is in situ. At first consideration, it would appear that "prophylactic surgery" would have a place in many hereditary malignancies; however, the procedure has applicability only if certain criteria are met: (1) the genetic mutation causing the hereditary malignancy must have a very high penetrance and be expressed regardless of environmental factors; (2) there must be a highly reliable test to identify patients who have inherited the mutated gene; (3) the organ must be removed with minimal morbidity and virtually no mortality; (4) there must be a suitable replacement for the function of the removed organ; and (5) there must be a reliable method of determining over time that the patient has been cured by "prophylactic surgery."

CONCLUSIONS

In this monograph we review several hereditary malignancies and consider those where prophylactic surgery might be useful. As we learn, there are various barriers to performing the procedure in many common hereditary cancer syndromes. The archetype disease syndromes, which meet each of the five criteria mentioned above and where prophylactic surgery is most useful, are the type 2 multiple endocrine neoplasia (MEN) syndromes: MEN2A, MEN2B, and the related familial medullary thyroid carcinoma. An additional benefit of the Human Genome Project, has been the development of pharmacologic and biologic compounds that block the metabolic pathway(s) activated by specific genetic mutations. Many of these compounds have shown efficacy in patients with locally advanced or metastatic cancers, and there is the likelihood that they will prove beneficial in preventing the outgrowth of malignant cells in patients destined to develop a hereditary cancer.

An introduction to managing medullary thyroid cancer

MTC is a rare neuroendocrine thyroid tumour accounting for 3% to 10% of all thyroid malignancies. It can occur in a sporadic and a hereditary clinical setting. Hereditary MTC may either occur alone (familial MTC, FMTC) or as part of multiple endocrine neoplasia (MEN) type 2A, or MEN 2B. These disorders are due to germline mutations in the RET (REarranged during Transfection) gene. In carriers of MEN 2B-associated RET mutations, prophylactic thyroidectomy is indicated before the first year of life. In the case of MEN 2A-associated germline RET mutations with a high-risk profile, total thyroidectomy is warranted before the age of 2 years and certainly before the age of 4 years. At that age the risk of invasive MTC and metastases is acceptably low. Depending on the type of RET mutation, thyroidectomy can take place at an older age in patients with a lower risk profile. In case of elevated basal or stimulated serum calcitonin, preventive surgery including total thyroidectomy and central compartment dissection should be performed regardless of age. When MTC presents as a palpable tumour, total thyroidectomy should be combined with extensive lymph node dissection of levels II-V on both sides and level VI to prevent locoregional recurrences.

Multiple endocrine neoplasia: paediatric perspective

Neuroendocrine tumours constitute a heterogeneous association of neoplasms, originated from a common precursor cell population. They include endocrine glands, such as the pituitary, the parathyroids, the cells of the neuroendocrine adrenals, endocrine islets within glandular tissue (thyroid, pancreas) and dispersed cells (diffuse endocrine system). Neuroendocrine tumours can occur sporadically or in a familial context, such as multiple endocrine neoplasia (MEN) syndromes. These are inherited autosomal dominant cancer syndromes, transmitted with 100% penetrance. They are categorized into MEN type 1 and type 2. The dream of each physician who treats cancer is to develop a strategy that will have a significantly favourable impact on morbidity and mortality associated with malignant tumours. This has been achieved as a result of improved screening and early treatment strategies in MEN. MEN 2 and medullary thyroid carcinoma (MTC) are of special relevance in childhood, because they require urgent and early diagnosis and treatment. The explication of the genetic basis of MTC has revolutionised management of the familial forms of this tumour.

Iodine 123 metaiodobenzylguanidine radio-guided navigation surgery for recurrent medullary thyroid carcinoma in a girl with multiple endocrine neoplasia type 2B

Multiple endocrine neoplasia type 2B (MEN 2B) is an inherited cancerous syndrome characterized by medullary thyroid carcinoma (MTC), adrenal pheochromocytoma, marfanoid habitus, and enteric ganglioneuromatosis. In this syndrome, a high frequency of persistent elevation of the serum calcitonin level, a sensitive marker for MTC, after total thyroidectomy has been reported, and the prognosis of such patients depends upon complete resection of recurrent MTC by repeated surgery. The authors performed iodine 123 metaiodobenzylguanidine ((123)I-MIBG) radio-guided navigation surgery for recurrent MTC in a 14-year-old girl with MEN 2B. She had undergone 4 neck operations, including total thyroidectomy at the age of 7 years. An intravenous injection of 100 MBq (123)I-MIBG was followed by the fifth surgery. At surgery, the cervical and upper mediastinal areas were filled with adhesional scar tissue, in which a gamma-scintillation probe conducted hot spots of isotope uptake by cancerous cells. Histopathology of resected specimens showed scattered nests of MTC cells corresponding to gamma-scintillation counts. Intraoperative (123)I-MIBG scanning is of substantial benefit for children with MEN 2B undergoing surgery for recurrent MTC.

A Drosophila model of multiple endocrine neoplasia type 2

Dominant mutations in the Ret receptor tyrosine kinase lead to the familial cancer syndrome multiple endocrine neoplasia type 2 (MEN2). Mammalian tissue culture studies suggest that RetMEN2 mutations significantly alter Ret-signaling properties, but the precise mechanisms by which RetMEN2 promotes tumorigenesis remain poorly understood. To determine the signal transduction pathways required for RetMEN2 activity, we analyzed analogous mutations in the Drosophila Ret ortholog dRet. Overexpressed dRetMEN2 isoforms targeted to the developing retina led to aberrant cell proliferation, inappropriate cell fate specification, and excessive Ras pathway activation. Genetic analysis indicated that dRetMEN2 acts through the Ras-ERK, Src, and Jun kinase pathways. A genetic screen for mutations that dominantly suppress or enhance dRetMEN2 phenotypes identified new genes that are required for the phenotypic outcomes of dRetMEN2 activity. Finally, we identified human orthologs for many of these genes and examined their status in human tumors. Two of these loci showed loss of heterozygosity (LOH) within both sporadic and MEN2-associated pheochromocytomas, suggesting that they may contribute to Ret-dependent oncogenesis.

Diagnosis and management of medullary thyroid carcinoma

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

Early malignant progression of hereditary medullary thyroid cancer

BACKGROUND

An age-related progression from C-cell hyperplasia to medullary thyroid carcinoma is associated with various germ-line mutations in the rearranged during transfection (RET) proto-oncogene that could be used to identify the optimal time for prophylactic surgery.

METHODS

In this European multicenter study conducted from July 1993 to February 2001, we enrolled patients who had a RET point mutation in the germ line, were 20 years of age or younger, were asymptomatic, and had undergone total thyroidectomy after confirmation of the RET mutation. Exclusion criteria were medullary thyroid carcinomas of more than 10 mm in greatest dimension and distant metastasis.

RESULTS

Altogether, 207 patients from 145 families were identified. There was a significant age-related progression from C-cell hyperplasia to medullary thyroid carcinoma and, ultimately, nodal metastasis in patients whose RET mutations were grouped according to the extracellular- and intracellular-domain codons affected and in those with the codon 634 genotype. No lymph-node metastases were noted in patients younger than 14 years of age. The age-related penetrance was unaffected by the type of amino acid substitution encoded by the various codon 634 mutations. The codon-specific differences in the age at presentation of cancer and the familial rates of concomitant adrenal and parathyroid involvement suggest that the risk of progression was based on the transforming potential of the individual RET mutation.

CONCLUSIONS

These data provide initial guidelines for the timing of prophylactic thyroidectomy in asymptomatic carriers of RET gene mutations.

Prophylactic Thyroidectomy in Men 2A Syndrome

Genetic testing is the appropriate procedure in MEN 2A syndrome for the early diagnosis of medullary carcinoma even at a preclinical stage. Prophylactic total thyroidectomy represents the standard preventive and therapeutic surgical approach in the treatment of medullary thyroid carcinoma in MEN 2A syndrome. Our experience has confirmed the presence of CCH and medullary thyroid carcinoma even in clinically negative patients, in agreement with reports in the literature.

Second malignancies in pediatric patients: imaging findings and differential diagnosis

Therapeutic advances in the treatment of pediatric neoplasms have improved the prognosis but have also increased the risk of developing rare second malignant neoplasms (SMNs). Primary neoplasms that are often associated with SMNs include lymphoma, retinoblastoma, medulloblastoma, neuroblastoma, and leukemia. The most common SMNs are central nervous system (CNS) tumors, sarcomas, thyroid and parotid gland carcinomas, and leukemia, particularly acute myeloblastic leukemia. Genetic predisposition, chemotherapy, and especially radiation therapy are implicated as pathogenic factors in SMN. All survivors of childhood cancer should have lifelong follow-up, preferably with magnetic resonance imaging, which does not require ionizing radiation and provides greater anatomic detail and resolution in the head and neck region and the CNS. A new or progressive lesion may represent recurrence of the primitive neoplastic process, late radiation injury, or, more infrequently, an SMN. Differential diagnosis can be very difficult, and outcome is often fatal. Treatment protocols should be modified to reduce the risk for SMN without compromising the effectiveness of initial therapy. Clinicians should individualize treatment for patients who are genetically predisposed to SMN. In addition, radiologists should be familiar with the long-term consequences of antineoplastic therapy to facilitate diagnosis and anticipate adverse outcomes.

Malignant progression from C-cell hyperplasia to medullary thyroid carcinoma in 167 carriers of RET germline mutations

BACKGROUND

Hereditary medullary thyroid carcinoma (MTC) is the most common and potentially life-shortening phenotypic manifestation of RET (rearranged during transfection) germline mutations. If a distinct time lag between the successive stages of malignant progression were identifiable, the information could be used to individualize prophylactic surgery. The study objective was to investigate the impact of RET genotype on disease progression from C-cell hyperplasia (CCH) to MTC.

METHODS

An institutional series of 167 (67 index, 100 nonindex) consecutive carriers of RET gene point mutations in exons 10, 11, 13, 14, or 16 who underwent total thyroidectomy between November 1994 and November 2002.

RESULTS

Regarding codons 618, 620, 634, 768, 790, and 804, patient age at diagnosis differed significantly depending on the type of pathology encountered (CCH, MTC without and with nodal metastasis). The variability in age, which may reflect the number of necessary somatic mutations, explained the pathological strata in 38% (codon 634) to 77% (codon 768) of patients. Conversely, 62% (codon 634) to 23% (codon 768) of variability in age at different pathological strata may have been determined by the RET genotype.

CONCLUSIONS

The pace of malignant progression of the RET genotype should be taken into account when considering prophylactic thyroidectomy in RET gene carriers.

Acceptable age for prophylactic surgery in children with multiple endocrine neoplasia type 2a

AIMS

Germline mutated RET proto-oncogene, causing multiple endocrine neoplasia (MEN)-2a syndrome is the indication for prophylactic total thyroidectomy. Literature regarding the risk and the extent of early surgical intervention is scarce and the optimum age for surgery is still controversial. To optimize management in these young children we evaluate our experience and results.

PATIENTS AND METHODS

From 1990 to 2001 preventive total thyroidectomy was performed in 13 MEN-2a gene carriers (4 boys and 9 girls; median age 7 (4-14) years). Preoperative assessment, surgical procedure, pathological examination, postoperative complications and treatment results were studied.

RESULTS

Surgery existed of a total thyroidectomy alone (n=3) in children with normal basal calcitonin and in combination with tracheo-esophageal exploration (n=6) or central compartment dissection (n=4) in case of abnormal calcitonin levels. Eight children presented with medullary thyroid cancer (MTC), three (median: 5 (4-12) years) with microscopic MTC and five (median 6 (4-14) years) with frank invasive MTC. Four of these five patients were younger than 6 years. Except for long-lasting hypoparathyroidism in one patient there were no complications. At a median follow-up of 6.5 years all patients are disease free.

CONCLUSION

MTC in RET mutated MEN-2a gene carriers in childhood are found at the age of 4 years. Therefore, DNA testing should be done preferably before that age. Preventive surgery can be performed safely at that age and may be limited to total thyroidectomy when baseline calcitonin levels are normal.

Prophylactic thyroidectomy in multiple endocrine neoplasia: the impact of molecular mechanisms of RET proto-oncogene

BACKGROUND

Multiple endocrine neoplasia (MEN) type 2, a cancer syndrome inherited in the dominant fashion, is defined by the occurrence of medullary thyroid carcinoma (MTC), either as a singular lesion (familial medullary thyroid carcinoma, FMTC) or with the variable expression of pheochromocytoma, hyperparathyroidism (MEN 2A), ganglioneuromas, buccal neuromas and Marfanoid-like phenotype (MEN 2B).

DISCUSSION

Germline mutations of the RET proto-oncogene, localized on chromosome 10q11.2, have been identified as the underlying genetic cause of the disorder. In the majority of patients with MEN 2A/FMTC missense mutations at exon 10 or exon 11 are identifiable. Cysteine to arginine exchange at codon 634 is the mutation most frequently found. In MEN 2B approximately 95% of patients present with a mutation at codon 918 (exon 16). Additionally, less frequent mutations in other codons have been found in both syndromes. The DNA-based genotype analysis enables the identification of gene carriers at risk of developing MTC and offer them prophylactic thyroidectomy prior to development of any thyroid pathologies. Prophylactic surgery is generally recommended for MEN 2A/FMTC gene carriers at the age of 4-6 years. Due to the aggressiveness of the MEN 2B syndrome gene carriers should be operated by the age of 1 year. Presumably some less virulent mutations allow postponement of the prophylactic treatment to the second to fourth decade of life.

CONCLUSIONS

Compared to standard presymptomatic biochemical screening, genetic testing and consecutive prophylactic treatment contribute to better outcome of individuals at risk for MTC.

Review of multiple endocrine neoplasia type 2A in children: therapeutic results of early thyroidectomy and prognostic value of codon analysis

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.

Prolonged survival of a patient with multiple endocrine neoplasia type 2b and stage IV medullary thyroid carcinoma

OBJECTIVE

To present a case of multiple endocrine neoplasia type 2B (MEN2B) with a prolonged course.

METHODS

We describe the clinical, laboratory, and radiologic findings in a patient with MEN2B and review the various interventions during a period of approximately 3 decades.

RESULTS

In 1962, a 19-year-old man with a marfanoid body habitus presented with multiple thyroid nodules and neurofibromas of the tongue. Total thyroidectomy demonstrated multicentric medullary thyroid carcinoma with cervical lymph node metastatic involvement. At the time of the first description of the MEN2B syndrome, the patient was enrolled in a surveillance program. An increase in urinary metanephrines resulted in bilateral adrenalectomy for multinodular pheochromocytoma in 1972. Increased serum calcitonin levels and the appearance of cervical lymphadenopathy led to modified radical neck dissection 12 years after the initial diagnosis of medullary thyroid carcinoma. In 1975, angiography revealed extensive hepatic lesions metastatic from the medullary thyroid carcinoma; this finding was confirmed by open liver biopsy in 1988. The patient lived 16 years after the initial diagnosis of liver metastatic disease and died 29 years after the initial examination.

CONCLUSION

The 3-decade course of this patient not only represents a classic case of MEN2B but also allows us to present the history of this disease from its discovery to the current era of genetic testing and exemplifies the possibility of long-term survival in a patient with liver metastatic involvement from medullary thyroid carcinoma.

Genetic predisposition and screening in pediatric cancer

Pediatricians are often the health care providers who first detect the signs and symptoms of childhood cancer. Although pediatric malignancies are rare diseases, early diagnosis is an important factor leading to high cure rates of many types of cancers including retinoblastomara, Wilms' tumor, hepatoblastoma, rhabdomyosarcoma. thyroid carcinoma, and other solid tumors. A number of familial cancer syndromes present with childhood cancers that can be recognized or diagnosed by pediatricians. The genetic origins of several syndromes have been elucidated. Genetic testing is not yet available for all of these inherited cancers. A frequently updated list of genetic tests is available at www.genetests.org. The ordering and interpreting of genetic tests, however, is often best done by trained genetic counselors. The pediatrician will play a vital on-going role in following the at-risk child. In many of syndromes discussed, the cost effectiveness of the tests as well as that of any potential intervention needs further study. The role of the subtle genetic polymorphisms in pediatric tumorigenesis. many more of which will undoubtedly be described in the coming years, has not yet been translated into defined needs for interventions. Perhaps in the future it will be possible to understand the additive effect of multiple genetic polymorphisms and to determine genetic profiles of high cancer risk. Until suitable interventions are established, however, the study of genetic variability and cancer will await practical significance. Undoubtedly other major important cancer genes are yet to be discovered and characterized. An additional challenge is the counseling and management of children and adults who have a strong family history of cancer yet who do not have a recognizable syndrome. The role of the primary pediatrician is to recognize the major cancer genetic syndromes, to make appropriate referrals for genetic counseling and testing when indicated, and to ensure that adequate screening tests are being done.

Prophylactic thyroidectomy in MEN 2A syndrome: experience in a single center

BACKGROUND

Genetic study of the RET proto-oncogene has modified the management, treatment, and prognosis of medullary thyroid carcinoma (MTC), multiple endocrine neoplasia 2A (MEN 2A), for patients with less advanced tumor stages. Classically, the diagnosis was based on an increase in basal and poststimulus peak calcitonin (bCT and pCT). Prophylactic thyroidectomy, based on results of genetic testing, may reduce recurrences in MTC.

STUDY DESIGN

Of 82 MTC (MEN 2A) patients genetically diagnosed and surgically treated at our center, 22 received a prophylactic thyroidectomy (RET +, bCT and pCT with normal values and asymptomatic). We analyzed age, gender, phenotype, RET mutation, cervical ultrasound, laboratory tests (bCT, pCT, and CEA), surgery, histologic data, TNM, and followup.

RESULTS

The 22 patients belonged to 8 families with MTC (MEN 2A). Mean age was 15.2 years (range 5 to 36 years). The RET mutation in 21 patients was Cys-->Tyr and in the remaining patient both in codon 634 in exon 11. The median values of bCT and pCT were 38 pg/mL (range < 15 to 75 pg/mL) and 148.5 pg/mL (range < 15 to 250 pg/mL), respectively. Total thyroidectomy was performed in 8 patients (age < or = 10 years) and associated central neck dissection in 14 patients (age> 10 years). Histologic study showed 7 C-cell hyperplasias and 15 MTCs (8 bilateral); the median size was 0.2 cm (range < 0.1 to 0.7cm); 1 patient had metastatic adenopathies. According to TNM, 7 were stage 0, 14 were stage I, and 1 was stage III. Postsurgery bCT and pCT values were normal in all patients, with a curative rate of 100%. MTC patients compared with C-cell hyperplasia patients were older on average, had higher mean bCT, mean pCT, and mean CEA.

CONCLUSIONS

Prophylactic thyroidectomy based on genetic testing allows identification and treatment of patients at an early stage of the disease and decreases recurrence rates. pCT values above the upper limit of normal may be markers for the presence of MTC and should be considered in selecting operative procedures for these patients.

Multiple endocrine neoplasia 2A syndrome: Surgical management

BACKGROUND/PURPOSE

Currently, molecular genetic diagnostics allow familial types of medullary thyroid carcinoma to be detected at an asymptomatic stage and surgery thus to be performed at a time when prognosis is good. The current report aims to determine the appropriate age for safe prophylactic thyroidectomy in children with multiple endocrine neoplasia (MEN) 2A and mutations at codon 609 according to genotype-phenotype correlations and will discuss surgical procedures.

METHODS

The authors describe the case of a family with hereditary MEN 2A syndrome. A DNA analysis of 7 family members confirmed the diagnosis by a mutation at codon 609 of the RET proto-oncogene.

RESULTS

A phaeochromocytoma developed in 2 family members. Four had medullary thyroid carcinoma. A grandson underwent a prophylactic thyroidectomy at the age of 5 on account of genetic evidence. Despite the negative preoperative and intraoperative findings he already had an invasive medullary thyroid carcinoma.

CONCLUSIONS

Few genotype-phenotype correlations have been established for MEN 2A disease. According to the natural history of the disease, families with the genotype RET cys609gly should have a more benign disease than high-risk families (mutations at codon 634, 618). From this report the authors conclude that prophylactic thyroidectomy in "609" families should be performed earlier than actually recommended, favorably at the age of 2 to 4 years. Further multicenter studies are needed to provide more clinical and prognostic data for less frequent (codon 609, 630, 791, and 891) RET genotypes.

Multiple endocrine neoplasia type 2a (MEN2a): a call for psycho-social research

This paper summarizes what is known about the diagnosis, treatment, and follow-care of people with the inherited disorder multiple endocrine neoplasia type 2a (MEN2a). Several databases were searched throughout the year 2000, including MEDLINE, CINAHL, CancerLit, PsychINFO, and Dissertation Abstracts International. MEN2a is a complex disease involving cancer care and control by surgery, health maintenance, and life-long observation of gene mutation carriers. Genetic testing is the standard of care, prophylactic surgery is recommended during directive counseling, and life-long surveillance is encouraged for people with MEN2a. A substantial body of scientific literature describes morbidity and mortality outcomes of disease treatment, and the monitoring of multiple organ systems. Research is scant concerning the psychological consequences and social impact of the MEN2a diagnosis, treatment, and follow-up. Nearly all that is known from a psycho-social perspective comes from data in The Netherlands. Little is known of the psychological responses to and social consequences of genetic predisposition testing, prophylactic and curative surgery, and life-long surveillance. Psycho-social research is essential to provide comprehensive care for patients and family members with this disorder and it is necessary to guide the development of risk management strategies for patients with this inherited cancer syndrome. Since MEN2a has been labeled a prototype for medical genetics, information on MEN2a patient experiences may be relevant to the care of individuals with other inherited cancer syndromes.

Early onset of medullary thyroid carcinoma in a kindred with multiple endocrine neoplasia type iia associated with cutaneous lichen amyloidosis

OBJECTIVE

To describe the molecular characterization of a kindred affected by the rare variant of multiple endocrine neoplasia type IIA (MEN IIA) associated with cutaneous lichen amyloidosis and to discuss the clinical implications in the management of this syndrome.

METHODS

A kindred with four affected family members was identified, and DNA analysis was performed by sequencing exon 11 of the RET proto-oncogene. Presymptomatic genetic screening was offered to all first-degree relatives.

RESULTS

Sequencing analysis of the RET proto-oncogene revealed a Cys634Trp (TGC->TGG) mutation in all clinically affected family members and in an asymptomatic 5-year-old child who, after thyroidectomy, was found to have multicentric medullary thyroid carcinoma and C-cell hyperplasia. A Gly691Ser (GGT->AGT) polymorphism was also detected in this family but did not segregate with the disease.

CONCLUSION

To our knowledge, this is the earliest detection of medullary thyroid carcinoma reported thus far in a kindred with MEN IIA associated with cutaneous lichen amyloidosis, and this finding suggests that prophylactic thyroidectomy, in kindreds with this variant, should be performed before the age of 5 years.

Medullary thyroid carcinoma as part of a multiple endocrine neoplasia type 2B syndrome: influence of the stage on the clinical course

BACKGROUND

Multiple endocrine neoplasia type 2B (MEN 2B) is an exceptional syndrome, for which the optimal age of thyroidectomy is poorly established and the course of medullary thyroid carcinoma (MTC) is ill-defined.

PATIENTS

All the 18 patients with a MEN 2B syndrome examined at the Institut Gustave Roussy were included in a single-center retrospective study.

RESULTS

There were 9 men and 9 women with a mean age of 13 years (range, 2-27 years) at diagnosis. The diagnosis of MTC was based on the presence of a thyroid nodule or involved neck lymph nodes and on dysmorphic features of MEN 2B in 60% and 40% of the cases, respectively. The classic M918T mutation in exon 16 was found in the 16 patients in whom it was investigated. At diagnosis, 2 patients had Stage I MTC, 15 patients had Stage III, and 1 patient had Stage IV disease. T1 MTC was found in 4 patients aged 2.1-3.7 years. However, two of these patients already had N1 disease. One patient with Stage I MTC, aged 3.4 years and 2 patients with Stage III disease, aged 14 and 25 years, had undetectable basal calcitonin (CT) after initial surgery. During follow-up, basal CT became detectable in one of three patients. Among the 15 other patients with an elevated postoperative CT level, metastases were demonstrated in 5 patients after a mean follow-up of 2 years. Five patients died, three of MTC, one of the MEN 2B syndrome, and one of intercurrent disease. Five- and 10-year overall survival rates were 85% and 75%, respectively.

CONCLUSIONS

This study confirms the need for early treatment of MTC in patients with the MEN 2B syndrome, preferably within the first 6 months of life. The phenotype of MTC occurring in the MEN 2B syndrome was not more aggressive than sporadic MTC or MTC occurring in other familial syndromes.

From eyelid bumps to thyroid lumps: report of a MEN type IIb family and review of the literature

PURPOSE

We present a two-generation family with multiple endocrine neoplasia (MEN) type IIb diagnosed by their ophthalmologists based on characteristic ophthalmic findings.

METHODS

A family consisting of a 33-year-old female proband and her 8- and 7-year-old children had prominent corneal nerves; eyelid, lip, and tongue nodules; and a characteristic facies. A polymerase chain reaction-based genetic assay was obtained to detect the genetic mutation most commonly associated with MEN type IIb. Serum calcitonin and urine catecholamine studies were obtained.

RESULTS

Molecular genetic studies detected in all 3 patients a mutation at codon 918 of the RET proto-oncogene known to be present in 95% of the cases of MEN type IIb. Serum calcitonin was elevated in the proband and her son. Urine catecholamine levels were elevated in the proband. Surgical treatment and histologic analysis confirmed pheochromocytoma and medullary thyroid carcinoma (MTC) in the proband. Surgical exploration revealed the MTC to be metastatic to the liver.

CONCLUSIONS

This family demonstrates the characteristic findings of MEN type IIb: prominent corneal nerves in a clear stroma and multiple submucosal neuromas of the conjunctiva, eyelids, lips, and tongue. Ophthalmologists have a critical role to play in recognizing these signs, because the early diagnosis of medullary thyroid carcinoma and pheochromocytoma may be life saving.

Thyroid disease

In summary, disease of the thyroid gland is common. Anaesthetists will be required to manage patients with hypothyroidism and hyperthyroidism and those requiring thyroidectomy. Since anaesthesia for thyroidectomy provides many challenges of airway management, the anaesthetist should pay particular attention to preoperative assessment of the airway and should be able to deal with acute airway complications in the perioperative phase.

Medullary carcinoma of the thyroid

Medullary thyroid cancer (MTC) is a distinct C-cell tumor of the thyroid. We review the oncogenesis and management of both sporadic tumors and those tumors arising as part of specific inherited syndromes. The RET proto-oncogene plays a role in the development of inherited forms of MTC and has become important in the clinical management of patients and their families. The recognition of the high rate of regional nodal involvement has led to lymphadenectomy being strongly considered for patients undergoing thyroidectomy for MTC.