The relationship between specific RET proto-oncogene mutations and disease phenotype in multiple endocrine neoplasia type 2. International RET mutation consortium analysis

CDKN1B mutation analyses and biochemical characteristics in patients with symptomatic or asymptomatic primary hyperparathyroidism

Purpose: The aim of this study was to compare clinical, biochemical and treatment modalities of the patients with symptomatic and asymptomatic PHPT (primary hyperparathyroidism), and evaluate whether the CDKN1B mutation from these patients contributes to the pathogenesis of typical, sporadic parathyroid adenomas. Materials and Methods: In this prospective study 80 patients (66 women and 14 men, mean age 50.8 ± 12.01 years) with PHPT were enrolled. Biochemical and clinical information were collected on patients’ sex, age, biochemical examination and radiological findings (nuclear 99 mTc sestamibi scans scintigraphy, cervical ultrasound). CDKN1B sequencing, and DNA isolation was performed by using GeneMATRIX Quick Blood DNA Purification Kit. Selected primer of CDKN1BF (rs786201010, c.-456_-453delCCTT) (CAGGTTTGTTGGCAGCAGTA) and CDKN1BR (rs786201010, c.-456_-453delCCTT) (GGAGCCAAAAGACACAGACC) were amplified by polymerase chain reaction (PCR) (Solis Biodyne, Estonia). Results: A total of 80 patients diagnosed with PHPT were included, of which 22 were symptomatic. Serum calcium and 24-hour calcium excretion were significantly increased in patients with symptomatic PHTP. Serum PTH levels were similar between the two group. PHPT. CDKN1B mutation was not detected in any patients. Conclusion: Symptomatic patients were found to have elevated levels of calcium levels (hypercalcaemic), 24-hour urine calcium excretion and target organ damage (bone disease and nephrolithiasis). Independent of PTH levels, clinical signs and symptoms could be related with serum calcium parameters in these patients.

RET receptor signaling: Function in development, metabolic disease, and cancer

The RET proto-oncogene encodes a receptor tyrosine kinase whose alterations are responsible for various human cancers and developmental disorders, including thyroid cancer, non-small cell lung cancer, multiple endocrine neoplasia type 2, and Hirschsprung's disease. RET receptors are physiologically activated by glial cell line-derived neurotrophic factor (GDNF) family ligands that bind to the coreceptor GDNF family receptor α (GFRα). Signaling via the GDNF/GFRα1/RET ternary complex plays crucial roles in the development of the enteric nervous system, kidneys, and urinary tract, as well as in the self-renewal of spermatogonial stem cells. In addition, another ligand, growth differentiation factor-15 (GDF15), has been shown to bind to GFRα-like and activate RET, regulating body weight. GDF15 is a stress response cytokine, and its elevated serum levels affect metabolism and anorexia-cachexia syndrome. Moreover, recent development of RET-specific kinase inhibitors contributed significantly to progress in the treatment of patients with RET-altered cancer. This review focuses on the broad roles of RET in development, metabolic diseases, and cancer.

Calcitonin and complementary biomarkers in the diagnosis of hereditary medullary thyroid carcinoma in children and adolescents

OBJECTIVES

Medullary thyroid carcinoma (MTC) is a rare malignancy that is effectively curable by surgery. Unlike in adults, hereditary MTC has a predominant role in children. A fast and safe diagnosis is important to assure the good prognosis for the patients. A major cornerstone is the assessment of biomarkers, but the interpretation must respect their pre-, post- and analytical features. Especially calcitonin (Ctn) is a challenging biomarker in daily laboratory diagnostics. However, Ctn is of particular relevance for the diagnostic in MTC. The American Thyroid Association recommends thyroidectomy if the upper reference range of Ctn is exceeded. Interestingly, age-dependent reference ranges for children and adolescents have become available only recently for Ctn assays. With this review, we aim to highlight the importance of a timely diagnosis of MTC in children and adolescents.

CONTENT

Recent developments in pediatric biochemical diagnostics of MTC were summarized. This includes guidance on interpretation of RET, Ctn, procalcitonin, carcinoembryonic antigen, carbohydrate antigen 19-9, and chromogranin A.

SUMMARY

Currently, Ctn is the most investigated biomarker in the diagnosis of MTC in children and adolescents. Other biomarkers as PCT suggest complementary evidence about pediatric MTC but their interpretation based largely on adult's data. A successful treatment of MTC requires, besides results of biomarkers, information about medical history, RET gene analysis and recent guideline knowledge.

OUTLOOK

More research is required to validate complementary biomarkers of Ctn in children. Additionally, the effect of different confounder on pediatric Ctn levels has to be further clarified.

The revised clinical practice guidelines on the management of thyroid tumors by the Japan Associations of Endocrine Surgeons: Core questions and recommendations for treatments of thyroid cancer

The Japan Associations of Endocrine Surgeons has developed the revised version of the Clinical Practice Guidelines for Thyroid Tumors. This article describes the guidelines translated into English for the 35 clinical questions relevant to the therapeutic management of thyroid cancers. The objective of the guidelines is to improve health-related outcomes in patients with thyroid tumors by enabling users to make their practice evidence-based and by minimizing any variations in clinical practice due to gaps in evidential knowledge among physicians. The guidelines give representative flow-charts on the management of papillary, follicular, medullary, and anaplastic thyroid carcinoma, along with recommendations for clinical questions by presenting evidence on the relevant outcomes including benefits, risks, and health conditions from patients' perspective. Therapeutic actions were recommended or not recommended either strongly (◎◎◎ or XXX) based on good evidence (😊)/good expert consensus (+++), or weakly (◎, ◎◎ or X, XX) based on poor evidence (😣)/poor expert consensus (+ or ++). Only 10 of the 51 recommendations given in the guidelines were supported by good evidence, whereas 35 were supported by good expert consensus. While implementing the current guidelines would be of help to achieve the objective, we need further clinical research to make our shared decision making to be more evidence-based.

5P Strategies for Management of Multiple Endocrine Neoplasia Type 2: A Paradigm of Precision Medicine

Multiple endocrine neoplasia type 2 (MEN2) is a neuroendocrine cancer syndrome characterized by medullary thyroid carcinoma, in combination or not with pheochromocytoma, hyperparathyroidism, and extra-endocrine features. MEN2 syndrome includes two clinically distinct forms subtyped as MEN2A and MEN2B. Nearly all MEN2 cases are caused by germline mutations of the RET proto-oncogene. In this review, we propose "5P" strategies for management of MEN2: prevention, prediction, personalization, psychological support, and participation, which could effectively improve clinical outcomes of patients. Based on RET mutations, MEN2 could be prevented through prenatal diagnosis or preimplantation genetic testing. Identification of pathogenic mutations in RET can enable early diagnosis of MEN2. Combining RET mutation testing with measurement of serum calcitonin, plasma or urinary metanephrine/normetanephrine, and serum parathyroid hormone levels could allow risk stratification and accurately prediction of MEN2 progression, thus facilitating implementation of personalized precision treatments to increase disease-free survival and overall survival. Furthermore, increased awareness of MEN2 is needed, which requires participation of physicians, patients, family members, and related organizations. Psychological support is also important for patients with MEN2 to promote comprehensive management of MEN2 symptoms. The "5P" strategies for management of MEN2 represent a typical clinical example of precision medicine. These strategies could effectively improve the health of MEN2 patient, and avoid adverse outcomes, including death and major morbidity, from MEN2.

Variability in Medullary Thyroid Carcinoma in RET L790F Carriers: A Case Comparison Study of Index Patients

Background: Previous studies have suggested that the variability in age of onset and aggressiveness of medullary thyroid carcinoma (MTC) in patients with multiple endocrine neoplasia type 2A (MEN 2A) carrying the same REarranged during Transfection (RET) mutation may be caused by additional RET germline variants or somatic variants. Methods: This study was a retrospective case comparison study of all MEN 2A index patients (n = 2) with the RET L790F germline mutation in Denmark. Whole blood and MTC tissue were analyzed for RET germline variants and other somatic variants (>500), respectively. Results: Patient 1 presented with MTC (T1aN1bM0) at age 14 years, while patient 2 presented with MTC (T1bN0M0) at age 70 years. No germline RET germline variants nor other variants were found to explain this MTC variability. Conclusions: We could not confirm the previously reported finding of a somatic RET variant as likely responsible for the early onset and aggressiveness of MTC in a RET germline mutation carrier. Also, we found no RET germline variants that could explain the MTC variability among our index patients. We did, however, identify a somatic FLT3 R387Q variant with an unknown potential as genetic modifier. Further large-scale studies are needed to investigate genetic modifiers in RET L790F carriers.

GDNF and the RET Receptor in Cancer: New Insights and Therapeutic Potential

The Glial cell line-derived neurotrophic Family Ligands (GFL) are soluble neurotrophic factors that are required for development of multiple human tissues, but which are also important contributors to human cancers. GFL signaling occurs through the transmembrane RET receptor tyrosine kinase, a well-characterized oncogene. GFL-independent RET activation, through rearrangement or point mutations occurs in thyroid and lung cancers. However, GFL-mediated activation of wildtype RET is an increasingly recognized mechanism promoting tumor growth and dissemination of a much broader group of cancers. RET and GFL expression have been implicated in metastasis or invasion in diverse human cancers including breast, pancreatic, and prostate tumors, where they are linked to poorer patient prognosis. In addition to directly inducing tumor growth in these diseases, GFL-RET signaling promotes changes in the tumor microenvironment that alter the surrounding stroma and cellular composition to enhance tumor invasion and metastasis. As such, GFL RET signaling is an important target for novel therapeutic approaches to limit tumor growth and spread and improve disease outcomes.

Overview of Genetically Determined Diseases/Multiple Endocrine Neoplasia Syndromes Predisposing to Endocrine Tumors

In this chapter, we present an overview of multiple endocrine neoplasia syndromes including their most important clinical and molecular features. Multiple endocrine neoplasia type 1 and 2 syndromes (MEN1 and MEN2) are discussed in detail. Syndromes that are presented in other chapters are only briefly mentioned. We discuss the relevance of germline gene alterations in apparently sporadic endocrine tumors, e.g., medullary thyroid cancer, primary hyperparathyroidism, and neuroendocrine tumors. McCune-Albright syndrome that only exists in non-hereditary, sporadic forms is also discussed in detail, as tumors of several endocrine organs can develop in the same individual.

A Pyrazolo[3,4-d]pyrimidin-4-amine Derivative Containing an Isoxazole Moiety Is a Selective and Potent Inhibitor of RET Gatekeeper Mutants

Aberrant RET kinase signaling plays critical roles in several human cancers such as thyroid carcinoma. The gatekeeper mutants (V804L or V804M) of RET are resistant to currently approved RET inhibitors such as cabozantinib and vandetanib. We, for the first time, report a highly selective and extremely potent RET inhibitor, 6i rationally designed. Compound 6i inhibits strongly RET gatekeeper mutants and other clinically relevant RET mutants as well as wt-RET. This substance also significantly suppresses growth of thyroid cancer-derived TT cell lines and Ba/F3 cells transformed with various RET mutants. Docking studies reveal that the isoxazole moiety in 6i is responsible for binding affinity improvement by providing additional site for H-bonding with Lys758. Also, 6i not only substantially blocks cellular RET autophosphorylation and its downstream pathway, it markedly induces apoptosis and anchorage-independent growth inhibition in TT cell lines while having no effect on normal thyroid Nthy ori-3-1 cells.

Pheochromocytomas and Paragangliomas: Clinical and Genetic Approaches

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are neuroendocrine tumors derived from the chromaffin tissue. Diagnosis of these tumors is extremely important as they are linked to the hypertension syndrome with great cardiovascular morbidity and mortality. A great majority of PCCs and PGLs are sporadic and benign tumors; however, the classic idea of 10% exception of these features is changing. The description of new genes linked to familial forms of PCC/PGLs, such as succinate dehydrogenase (SDH) complex subunits, KIF1Bβ, EGLN1, TMEM127, and MAX, added to the well-known PCC familial syndrome (MEN2, VHL, and neurofibromatosis type 1) presents new challenges for diagnosis. In this review, we discuss the diversity of clinical and genetic approaches to this syndrome as well the diverse criteria that should guide genetic investigation.

Paragangliomas/Pheochromocytomas: clinically oriented genetic testing

Paragangliomas are rare neuroendocrine tumors that arise in the sympathetic or parasympathetic nervous system. Sympathetic paragangliomas are mainly found in the adrenal medulla (designated pheochromocytomas) but may also have a thoracic, abdominal, or pelvic localization. Parasympathetic paragangliomas are generally located at the head or neck. Knowledge concerning the familial forms of paragangliomas has greatly improved in recent years. Additionally to the genes involved in the classical syndromic forms: VHL gene (von Hippel-Lindau), RET gene (Multiple Endocrine Neoplasia type 2), and NF1 gene (Neurofibromatosis type 1), 10 novel genes have so far been implicated in the occurrence of paragangliomas/pheochromocytomas: SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, MAX, EGLN1, HIF2A, and KIF1B. It is currently accepted that about 35% of the paragangliomas cases are due to germline mutations in one of these genes. Furthermore, somatic mutations of RET, VHL, NF1, MAX, HIF2A, and H-RAS can also be detected. The identification of the mutation responsible for the paraganglioma/pheochromocytoma phenotype in a patient may be crucial in determining the treatment and allowing specific follow-up guidelines, ultimately leading to a better prognosis. Herein, we summarize the most relevant aspects regarding the genetics and clinical aspects of the syndromic and nonsyndromic forms of pheochromocytoma/paraganglioma aiming to provide an algorithm for genetic testing.

Genetic and clinical features of multiple endocrine neoplasia types 1 and 2

Multiple endocrine neoplasia (MEN) are clinical inherited syndromes affecting different endocrine glands. Three different patterns of MEN syndromes can occur (MEN 1, MEN 2A, and MEN 2B). MEN syndromes are very rare, affect all ages and both sexes are equally affected. MEN 1 is characterized by the neoplastic transformation of the parathyroid glands, pancreatic islets, anterior pituitary, and gastrointestinal tract. Heterozygous MEN 1 germline mutations have been detected in about 70–80% of patients with MEN 1. The mutations are scattered throughout the entire genomic sequence of the gene. MEN 1 patients are characterized by variable clinical features, thus suggesting the lack of a genotype-phenotype correlation. Therapeutical approaches are different according to the different endocrinopathies. The prognosis is generally good if adequate treatment is provided. In MEN 2 syndromes, the medullary thyroid cancer (MTC) is almost invariably present and can be associated with pheochromocytoma (PHEO) and/or multiple adenomatosis of parathyroid glands with hyperparathyroidism (PHPT). The different combination of the endocrine neoplasia gives origin to 3 syndromes: MEN 2A, MEN 2B, and FMTC. The clinical course of MTC varies considerably in the three syndromes. It is very aggressive in MEN 2B, almost indolent in the majority of patients with FMTC and with variable degrees of aggressiveness in patients with MEN 2A. Activating germline point mutations of the RET protooncogene are present in 98% of MEN 2 families. A strong genotype-phenotype correlation has been observed and a specific RET mutation may be responsible for a more or less aggressive clinical course. The treatment of choice for primary MTC is total thyroidectomy with central neck lymph nodes dissection. Nevertheless, 30% of MTC patients, especially in MEN 2B and 2A, are not cured by surgery. Recently, developed molecular therapeutics that target the RET pathway have shown very promising activity in clinical trials of patients with advanced MTC. MEN 2 prognosis is strictly dependent on the MTC aggressiveness and thus on the success of the initial treatment.

Determination of RET Sequence Variation in an MEN2 Unaffected Cohort Using Multiple-Sample Pooling and Next-Generation Sequencing

Multisample, nonindexed pooling combined with next-generation sequencing (NGS) was used to discover RET proto-oncogene sequence variation within a cohort known to be unaffected by multiple endocrine neoplasia type 2 (MEN2). DNA samples (113 Caucasians, 23 persons of other ethnicities) were amplified for RET intron 9 to intron 16 and then divided into 5 pools of <30 samples each before library prep and NGS. Two controls were included in this study, a single sample and a pool of 50 samples that had been previously sequenced by the same NGS methods. All 59 variants previously detected in the 50-pool control were present. Of the 61 variants detected in the unaffected cohort, 20 variants were novel changes. Several variants were validated by high-resolution melting analysis and Sanger sequencing, and their allelic frequencies correlated well with those determined by NGS. The results from this unaffected cohort will be added to the RET MEN2 database.

Successful kidney transplantation in a patient with multiple endocrine neoplasia type 2A syndrome: case study

We present the case of a 37-year-old patient diagnosed with multiple endocrine neoplasia type 2A (MEN 2A) syndrome, as confirmed by genetic tests, who underwent the transplantation of a kidney from a cadaveric donor. MEN 2A, a hereditary autosomal dominant syndrome, is caused by the mutation of the RET proto-oncogene. In almost all patients this syndrome, is characterized by the occurrence of medullary thyroid cancer and pheochromocytoma; in some individuals also hyperparathyroidism. The available literature has not documented a kidney transplantation performed in Poland for this indication.

How to Treat a Signal? Current Basis for RET-Genotype-Oriented Choice of Kinase Inhibitors for the Treatment of Medullary Thyroid Cancer

The significance of RET in thyroid cancer comes from solid evidence that, when inherited, an RET activating mutation primes C-cells to transform into medullary carcinomas. Moreover, environmental exposure to radiation also induces rearranged transforming RET “isoforms” that are found in papillary thyroid cancer. The RET gene codes for a tyrosine kinase receptor that targets a diverse set of intracellular signaling pathways. The nature of RET point mutations predicts differences in the mechanisms by which the receptor becomes activated and correlates with different forms of clinical presentation, age of onset, and biological aggressiveness. A number of RET-targeting Tyrosine Kinase Inhibitors (TKIs) are currently undergoing clinical trials to evaluate their effectiveness in the treatment of thyroid cancer, and it is conceivable that the RET genotype may also influence response to these compounds. The question that now emerges is whether, in the future, the rational for treatment of refractory thyroid cancer will be based on the management of an abnormal RET signal. In this paper we address the RET-targeting TKIs and review studies about the signaling properties of distinct RET mutants as a means to predict response and design combinatorial therapies for the soon to be available TKIs.

Primary hyperparathyroidism as the first clinical manifestation of multiple endocrine neoplasia type 2A in a 5-year-old child

BACKGROUND

Primary hyperparathyroidism occurs in only 10%-30% of patients with multiple endocrine neoplasia type 2A (MEN2A), rarely as the sole clinical manifestation, and is usually diagnosed after the third decade of life.

SUMMARY

A 5-year-old girl was referred for prophylactic thyroidectomy as she carried the p.C634R RET mutation. She was clinically asymptomatic, with a normally palpable thyroid and with the cervical region free of lymphadenopathy or other nodules. Preoperative tests revealed hypercalcemia associated with elevation of parathyroid hormone (PTH) (calcium = 11.2 mg/dL, calcium ion = 1.48 mmol/L, phosphorus = 4.0 mg/dL, alkaline phosphatase = 625 U/L, parathyroid hormone (PTH) PTH = 998 pg/mL). A thyroid ultrasound was normal and parathyroid scintigraphy with (99m)Tc-Sestamibi revealed an area of radioconcentration in the upper half of the left thyroid lobe suggesting hyperfunctioning parathyroid tissue. She underwent total thyroidectomy and parathyroidectomy and developed hypocalcemia. The anatomopathological examination showed no histopathological changes in the thyroid tissue and an adenoma of the parathyroid gland, confirming the diagnosis of hyperparathyroidism.

CONCLUSIONS

Primary hyperparathyroidism can be a precocious manifestation of MEN2A. This case report highlights that asymptomatic hypercalcemia should be scrutinized in children related to patients with MEN2A who carry a mutation in the RET proto-oncogene, especially mutations in the codon 634, before the currently recommended age of 8 years.

RET genetic screening of sporadic medullary thyroid cancer (MTC) allows the preclinical diagnosis of unsuspected gene carriers and the identification of a relevant percentage of hidden familial MTC (FMTC)

OBJECTIVE

This study was aimed to demonstrate the clinical benefits of rearranged during transfection (RET) genetic screening in patients with apparently sporadic medullary thyroid cancer (MTC) not only to identify the hereditary nature of the disease in the index case but also to discover family members harbouring the same germline mutations (i.e. gene carriers) who are unaware of their condition.

CONTEXT

RET genetic screening allowed the identification of germline RET mutations in apparently sporadic MTC resulting in their re-classification as hereditary forms.

PATIENTS AND MEASUREMENTS

RET genetic screening was performed in 729 apparently sporadic MTC patients by direct sequencing RET exons 5, 8, 10, 11 and 13-16. Clinical and biochemical evaluation of gene carriers was also performed.

RESULTS

We discovered an unsuspected germline RET mutation in 47 of 729 (6·5%) apparently sporadic MTC who were re-classified as hereditary. We found 60 of 146 (41·1%) gene carriers, 35 of whom had biochemical or clinical evidence of MTC. Thirty gene carriers underwent total thyroidectomy and 27 of 30 (90%) were persistently cured after a mean follow-up of 6·0 years. As a further result of RET genetic screening, we observed a significantly higher prevalence of familial medullary thyroid cancer (FMTC) in our series with respect to the largest series of the International RET Consortium (P = 0·0002).

CONCLUSIONS

RET genetic screening of patients with apparently sporadic MTC represents a major tool for the preclinical diagnosis and early treatment of unsuspected affected family members and allows the identification of a relevant percentage of hidden FMTC.

Familial thyroid neoplasia: impact of technological advances on detection and monitoring

PURPOSE OF REVIEW

To weigh the clinical impact of new technological insights into heritable thyroid malignancies.

RECENT FINDINGS

Medullary thyroid carcinoma and familial nonmedullary thyroid cancers represent the small minority of thyroid cancers that are inherited. New insights into the genetic alterations and molecular mechanisms implicated in these tumors are serving to refine the clinical tools available for their initial diagnosis as well as subsequent follow-up. In addition to an analysis of rearranged during transfection mutations and calcitonin profiles in medullary thyroid carcinoma, this review includes emphasis on familial nonmedullary thyroid cancer syndromes, including genetic findings in familial papillary thyroid cancer, familial adenomatous polyposis, Cowden syndrome, Carney complex, and Werner syndrome.

SUMMARY

Genetic mutational information is increasingly available on medullary and familial nonmedullary thyroid cancer and their associated syndromes. The clinical significance of this information for affected patients and their families continues to undergo evaluation.

Mendelian genetics of rare--and not so rare--cancers

Mendelian genetics forms the basis for gene-informed risk assessment and management for the patient and family, and should be at the very foundation of 21st century personalization of healthcare. Yet this is an underutilized commodity. Identification and characterization of germline mutations in the RET proto-oncogene, encoding a receptor tyrosine kinase, as causing >90% of multiple endocrine neoplasia type 2 (MEN 2), an autosomal dominant disorder characterized by medullary thyroid cancer, pheochromocytoma, and hyperparathyroidism, heralded the era of evidence-based molecular diagnosis, predictive testing, genetic counseling, gene-informed cancer risk assessment, and preventative medicine. Since then, many syndromic endocrine neoplasias have proven to fall under this clinically utile and actionable model, such as those caused by mutations in RET, VHL, or SDHB-D. The familial risk associated with epithelial (nonmedullary) thyroid carcinoma is among the highest of all solid tumors, yet only a few highly penetrant heritable epithelial thyroid cancer syndrome exist. This is illustrated by Cowden syndrome, a difficult-to-recognize autosomal dominant disorder characterized by breast, thyroid, and other cancers, caused by germline mutations in PTEN, encoding a phosphatase, and minorly, SDHB/SDHD variants.

Clinical and molecular genetics of parathyroid neoplasms

Primary hyperparathyroidism (HPT) results from the excessive secretion of parathyroid hormone from parathyroid tumours. While most HPT is sporadic, it is associated with a familial syndrome in a minority of cases. The study of these syndromes has helped define the pathophysiology of both familial and sporadic parathyroid neoplasms. Investigation of kindred with multiple endocrine neoplasia type 1 (MEN1) and the hyperparathyroidism-jaw tumour syndrome (HPT-JT) led to the discovery of the tumour suppressor genes MEN1 and HRPT2. We now recognise that somatic mutations in MEN1 and HRPT2 tumour suppressor genes are frequent events in sporadic parathyroid adenomas and carcinomas, respectively. Parathyroid tumours in the MEN2A syndrome result from mutational activation of the RET oncogene. The CCND1/PRAD1 oncogene was discovered by analysis of sporadic parathyroid tumours. Studies of familial isolated HPT and analysis of chromosomal loss and gain in parathyroid tumours suggest that other genes relevant to parathyroid neoplasia await identification.

Old and new insights in the treatment of thyroid carcinoma

Thyroid cancer is the endocrine tumor that bears the highest incidence with 33 550 new cases per year. It bears an excellent prognosis with a mortality of 1530 patients per year (Jemal et al.; 2007). We have been treating patients with thyroid carcinoma during many years without many innovations. Recently, we have assisted to the development of new agents for the treatment of this disease with unexpected good results. Here we present a review with the old and new methods for the treatment of this disease.

Sporadic and familial medullary thyroid carcinoma: state of the art

Medullary thyroid cancer (MTC) accounts for 5% to 10% of all thyroid cancers. The high frequency of familial cases mandates screening and genetic testing. The aggressiveness and age of onset of familial MTC differs depending on the specific genetic mutation, and this should determine the timing and extent of surgery. Sporadic MTC can present at any age, and it is usually associated with a palpable mass and the presence of nodal metastases. Surgery is standard treatment for any patient presenting with resectable MTC. Further studies are needed to investigate the role of radiation therapy in the palliation and local control of postresection and advanced-stage MTC. New systemic therapies for metastatic disease are being investigated. Targeted molecular therapies, based on knowledge of the pathways affected by RET mutations, are being tested in multiple clinical trials.

Surgical management of MEN-1 and -2: state of the art

Multiple endocrine neoplasia syndrome type 1 (MEN-1) consists of endocrine tumors of the parathyroid, the endocrine pancreas-duodenum, and the pituitary. Surveillance and screening for the endocrinopathies is recommended in gene carriers. Surgery for MEN-1-related hyperparathyroidism is generally performed as radical subtotal parathyroidectomy, because less surgery is likely to result in persistent or recurrent disease. Multiple endocrine neoplasia syndrome type 2 (MEN-2) consists of medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. Prophylactic thyroidectomy based on DNA testing in the MEN-2 syndrome is considered one of the greater achievements in cancer treatment, because it may be performed before thyroid carcinoma development and provides cure for the patient.

Development and characterization of reference materials for MTHFR, SERPINA1, RET, BRCA1, and BRCA2 genetic testing

Well-characterized reference materials (RMs) are integral in maintaining clinical laboratory quality assurance for genetic testing. These RMs can be used for quality control, monitoring of test performance, test validation, and proficiency testing of DNA-based genetic tests. To address the need for such materials, the Centers for Disease Control and Prevention established the Genetic Testing Reference Material Coordination Program (GeT-RM), which works with the genetics community to improve public availability of characterized RMs for genetic testing. To date, the GeT-RM program has coordinated the characterization of publicly available genomic DNA RMs for a number of disorders, including cystic fibrosis, Huntington disease, fragile X, and several genetic conditions with relatively high prevalence in the Ashkenazi Jewish population. Genotypic information about a number of other cell lines has been collected and is also available. The present study includes the development and commutability/genotype characterization of 10 DNA samples for clinically relevant mutations or sequence variants in the following genes: MTHFR; SERPINA1; RET; BRCA1; and BRCA2. DNA samples were analyzed by 19 clinical genetic laboratories using a variety of assays and technology platforms. Concordance was 100% for all samples, with no differences observed between laboratories using different methods. All DNA samples are available from Coriell Cell Repositories and characterization information can be found on the GeT-RM website.

Familial medullary thyroid carcinoma associated with cutaneous lichen amyloidosis

BACKGROUND

This is a report of a patient with a novel genotype-phenotype relationship of a c804 mutation of the RET proto-oncogene manifesting as medullary thyroid carcinoma (MTC) and cutaneous lichen amyloidosis (CLA).

SUMMARY

Clinical data were obtained for patient appearance and laboratory results. Analyzed were histopathology of the skin lesion and thyroid gland, genetic mutation, and family pedigree. Skin histology and histochemistry were consistent with CLA. Serum calcitonin levels were moderately elevated. Thyroid histology demonstrated a 4 mm focus of MTC. Measurements of serum parathormone, calcium, and plasma metanephrines were normal. DNA analysis demonstrated a mutation in codon 804 of the RET proto-oncogene resulting in a Valine to Methionine (V804M) substitution. Genetic testing in two siblings revealed the same mutation.

CONCLUSIONS

This is the first description of a patient with CLA not associated with a mutation in codon 634. The patient is one of the few with a V804M mutation in whom the clinical expression did not fully conform to the definition of familial MTC.

Long term parathyroid function following total parathyroidectomy with autotransplantation in adult patients with MEN2A

While there is no doubt that total thyroidectomy is necessary for medullary thyroid carcinoma (MTC) in multiple endocrine neoplasia type 2A (MEN2A) patients, there is still controversy regarding the management of the parathyroid glands. Although most, but not all, endocrine surgeons leave normal-appearing parathyroid glands in situ during thyroid surgery for MEN2A, we have employed total parathyroidectomy with autotransplantation. Between 1994 and 2006, 12 MEN2A patients underwent therapeutic total or completion thyroidectomy and lymph nodes dissection at least in the central compartment for MTC. Total or completion parathyroidectomy with autotransplantation was performed concurrently with above-mentioned surgery. All patients were over 25 years old, and the median age was 48.5 years. There were 5 males and 7 females from 8 families. The average number of transplanted parathyroid glands was 3. Serum calcium and intact PTH levels have been maintained during the median follow up of 107 months in all patients except for one who of died of advanced MTC one year after surgery. Total parathyroidectomy with autotransplantation at the time of primary surgery for MTC, i.e. total thyroidectomy with bilateral central neck dissection, is a feasible approach for managing the risk of hyperparathyroidism.

Premonitory symptoms preceding metastatic medullary thyroid cancer in MEN 2B: An exploratory analysis

BACKGROUND

More than 90% of M918T carriers with multiple endocrine neoplasia type 2B (MEN 2B) harbor de novo mutations in the REarranged during Transfection (RET) protooncogene. DNA-based screening for RET germline mutations is rarely useful for early diagnosis, which thus is contingent on the clinical ascertainment of MEN 2B-specific symptoms as soon as they emerge. Little information exists about the presence of these symptoms in infancy.

METHODS

Detailed information was gathered regarding the development of MEN 2B-associated symptoms from the parents of 25 M918T RET carriers and 50 age- and sex-matched controls with the use of a disease-specific questionnaire.

RESULTS

Until the end of the study, at a median age of 16.2 (range, 0.5-34.9 years), all 25 M918T RET carriers had developed medullary thyroid cancer. By that time, 96%, 91%, 71%, 75%, and 28% of carriers displayed oral manifestations, ocular abnormalities, intestinal symptoms, musculoskeletal malformations, and pheochromocytoma, respectively. During the first year of life, fewer than 20% of carriers were found to express the typical MEN 2B phenotype, whereas 86% and 61% of these children, but none of the controls, were noted for their inability to cry tears and for constipation.

CONCLUSION

Because the classic MEN 2B phenotype is rare during the first year of life, more emphasis should be placed on the more subtle features of the syndrome. Additional studies are needed to validate the usefulness of the symptoms "inability to cry" and "constipation" for earlier diagnosis of MEN 2B.

New agents in the treatment for malignancies of the salivary and thyroid glands

The treatment of relatively rare malignancies, such as those of the salivary glands and iodine refractory thyroid cancer, has been invigorated by the development of novel molecular targeting agents. Accrual to clinical trials for these disease sites continues to be limited by their relatively low incidence. Nonetheless, multicenter collaborations have contributed greatly to the development of a number of emerging systemic therapies. This article briefly summarizes the epidemiology and pathogenesis of salivary gland and thyroid cancer, and then describes some of the new drugs under evaluation for these malignancies.

Multiple endocrine neoplasia syndromes

The multiple endocrine neoplasia (MEN) syndromes are rare autosomal-dominant conditions that predispose affected individuals to benign and malignant tumors of the pituitary, thyroid, parathyroids, adrenals, endocrine pancreas, paraganglia, or nonendocrine organs. The classic MEN syndromes include MEN type 1 and MEN type 2. However, several other hereditary conditions should also be considered in the category of MEN: von Hippel-Lindau syndrome, the familial paraganglioma syndromes, Cowden syndrome, Carney complex, and hyperparathyroidism jaw-tumor syndrome. In addition, researchers are becoming aware of other familial endocrine neoplasia syndromes with an unknown genetic basis that might also fall into the category of MEN. This article reviews the clinical features, diagnosis, and surgical management of the various MEN syndromes and genetic risk assessment for patients presenting with one or more endocrine neoplasms.

Multiple endocrine neoplasia

MEN1 and MEN2 are autosomal dominant cancer syndromes with the potential for considerable morbidity and mortality. Better understanding of the molecular pathogenesis in MEN1 and MEN2 has fostered the development of specific DNA screening. Knowing the genetic status of patients is valuable for making decisions regarding surveillance and interventions, such as prophylactic thyroidectomy for medullary thyroid cancer. Identifying new RET pathways has provided molecular targets for therapies that currently are being tested in clinical trials for locally advanced, metastatic, and recurrent medullary thyroid cancer.

Medullary thyroid cancer: targeting the RET kinase pathway with sorafenib/tipifarnib

Medullary thyroid carcinoma (MTC) is an uncommon malignancy of hereditary and sporadic presentation. Mutations in the RET proto-oncogene are involved in the pathogenesis of familial MTC and >50% of the sporadic cases. Currently, there is no effective treatment for recurrent or metastatic MTC. We report here a rapid response to a sorafenib (RET and RAF kinase and vascular endothelial growth factor receptor inhibitor)--based regimen in a patient with sporadic MTC who had advanced, progressive disease and a novel RET kinase aberration at exon 11 shown in tumor tissue.

RET proto-oncogene mutations are restricted to codons 634 and 918 in mainland Chinese families with MEN2A and MEN2B

OBJECTIVE

Multiple endocrine neoplasia type 2 is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene, which includes multiple endocrine neoplasia type 2A (MEN2A), type 2B (MEN 2B), and familial medullary thyroid carcinoma (FMTC). In this paper we present the phenotype-genotype correlation of 20 unrelated Chinese families with 15 cases of MEN2A and five cases of MEN2B.

DESIGN

Cross-sectional study.

PATIENTS

A total of 147 members from the 20 families were included. Among them, 119 family members were from MEN2A pedigrees (including 15 MEN2A probands) and 28 members from MEN2B pedigrees (including five MEN2B probands).

MEASUREMENTS

Genomic DNA was isolated from peripheral blood leucocytes and was amplified using polymerase chain reaction (PCR). DNA analysis for RET mutations in exons 8, 10, 11, 13, 14, 15 and 16 was performed with specific primers.

RESULTS

Thirty-seven MEN2A and five MEN2B patients were identified as having RET mutations. The incidence of medullary thyroid carcinoma (MTC), pheochromocytoma (PCC) and hyperparathyroidism (HPT) in the 37 MEN2A patients was 91.9, 56.8 and 10.8%, respectively; the onset of MTC in MEN2A patients was earlier than that of PCC and HPT. Five germline mutations, all located at codon 634 of exon11 in the RET proto-oncogene, were detected in all of the 37 MEN2A patients. The highest frequency of the five germline mutations was C634Y (46.7%), followed by C634R (26.7%), C634W (13.3%), C634F (6.7%) and C634S (6.7%). No statistical significance was found between the incidence of PCC and different genotypes of codon 634 in MEN2A patients, whereas the incidence of HPT was closely associated with C634R and C634Y. The gene mutation (M918T) at exon16 of the RET proto-oncogene was present in five MEN2B probands.

CONCLUSIONS

RET proto-oncogene mutations were restricted to codon 634 and 918 in Chinese families with MEN2A and MEN2B. In general the genetic characteristics of these patients with MEN2A and MEN2B reflect the general pattern around the world and it remains to be determined with larger studies in China whether Chinese patients have a different genetic pattern of mutations.

Pheochromocytoma: advances in genetics, diagnosis, localization, and treatment

Pheochromocytomas are rare, catecholamine-secreting tumors arising most frequently in the chromaffin cells of the adrenal glands. Recent studies have suggested that genetic mutations are more frequent than previously appreciated in patients with these lesions. Advances continue to be made not only in the genetic evaluation of these patients but also in the biochemical confirmation and tumor localization. Surgery remains the definitive treatment, and advances in laparoscopic techniques as well as cortical-sparing procedures have reduced the morbidity associated with tumor resection.

A family of multiple endocrine neoplasia type 2A (MEN 2A) with Cys630Tyr RET germline mutation: report of a case

Since the majority of multiple endocrine neoplasia type 2A (MEN 2A) patients have missense mutations at codon 634 and those with the Cys630 RET genotype mutations are extremely rare, limited clinical information is available about this rare type. We report here three members of one Japanese MEN 2A family with the Cys630Tyr genotype. A 67-year-old woman presented a firm thyroid nodule, and preoperative examination revealed medullary thyroid carcinoma with primary hyperparthyoidism and no pheochromocytoma. At surgery, bilateral medullary thyroid carcinomas and parathyroid adenoma were found. No lymph node metastasis was identified. Computed tomography scans and laboratory examination of blood have shown no evidence of tumor recurrence and no abnormality of parathyroid function during the 4 years after surgery. A 40-year-old man, the proband's son, was shown to have the same RET mutation, underwent total thyroidectomy prophylactically, and only microscopic foci of medullary thyroid carcinoma were found. A 10-year-old boy, the proband's grandson also having the same RET mutation, showed normal basal serum calcitonin level and has been followed up conservatively. To our knowledge, 18 patients of 6 families with the Cys630 mutations have been reported so far. This is only the second reported case with primary hyperparathyroidism. RET 630 mutations might be associated with lower penetrance of primary hyperparthyoidism and pheochromocytoma.

Asymptomatic bilateral adrenal pheochromocytoma in a patient with a germline V804M mutation in the RET proto-oncogene

A diagnosis of bilateral pheochromocytoma warrants exclusion of hereditary pheochromocytoma.

OBJECTIVE

To describe the first case of a bilateral pheochromocytoma associated with V804M mutation in the RET proto-oncogene.

PATIENTS

The index case was a 54-year-old man with bilateral adrenal masses discovered during a CT scan performed for other reasons.

MEASUREMENTS

Genetic analysis included exons 8-11 and 13-17 in the RET proto-oncogene, all four exons and flanking intronic regions in the SDHD gene, all eight exons and flanking intronic regions in the SDHB, and all three exons in the VHL gene.

RESULTS

Investigations revealed elevated urinary metanephrines (32.3 micromol/day), and laparoscopic bilateral adrenalectomy confirmed bilateral pheochromocytomas. A heterozygous V804M mutation in exon 14 of the RET was found in the index case and in four relatives. Total thyroidectomy, performed in four of five affected members in this kindred, disclosed a medullary thyroid carcinoma in the index case and in a 50-year-old woman, and nodular C-cell hyperplasia in the other two subjects.

CONCLUSIONS

This clinical case suggests that individuals carrying the germline V804M mutation should be screened annually for the presence of pheochromocytoma.

Medullary Thyroid Carcinoma

Medullary thyroid carcinoma is a neuroendocrine tumor derived from the C cells of the thyroid gland and accounts for approximately 5% of all thyroid carcinomas. Approximately 30% of the cases are associated with an autosomal dominant syndrome called multiple endocrine neoplasia type 2, and the identification of these individuals is important because affected family members may benefit from an early diagnosis. The treatment of this disease is predominantly surgical, and the impact of radiotherapy and chemotherapy is limited. The identification of the associated molecular events has lead to the development of specific molecular targeted agents that may change the way this disease is treated in the near future.

The multiple endocrine neoplasia syndromes

Multiple endocrine neoplasia (MEN) type 1 and type 2 exhibit an autosomal dominant pattern of inheritance. In the past two decades the germline mutations that cause these inherited syndromes have been identified. The large majority of patients with MEN1 have mutations in the menin gene. Mutations in the REarranged during Transfection (RET) gene cause MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC). Specific codon mutations within RET correlate with disease phenotype and severity. Also, children from families with MEN2A, MEN2B, or FMTC, who are found to have inherited a mutated RET allele, can be managed by prophylactic thyroidectomy, thus preventing the development of medullary thyroid carcinoma (MTC), the dominant endocrinopathy in patients with these hereditary syndromes. New insights into the molecular pathway of RET signal transduction are leading to novel targeted therapies in patients with locally advanced or metastatic hereditary MTC.