Genotype-phenotype based surgical concept of hereditary medullary thyroid carcinoma

Evaluation and Surgical Management of Multiple Endocrine Neoplasias

Multiple endocrine neoplasia (MEN) syndromes are rare autosomal dominant diseases that are associated with a mixture of both endocrine and non-endocrine tumors. Traditionally, there are 2 types of MEN that have unique clinical associations: MEN 1 (parathyroid hyperplasia, pancreatic neuroendocrine tumors, and pituitary tumors) and MEN 2 (medullary thyroid carcinoma and pheochromocytoma), which is further classified into MEN 2A (adds parathyroid adenomas) and 2B (adds ganglioneuromas and marfanoid habitus). Many of the endocrine tumors are resected surgically, and the pre, intra, and postoperative management strategies used must take into account the high recurrence rates asscioated with MEN tumors.

Does Genotype-Specific Phenotype in Patients with Multiple Endocrine Neoplasia Type 2 Occur as Current Guidelines Predict?

The clinical manifestation of multiple endocrine neoplasia type 2 (MEN2) in terms of developing medullary thyroid cancer (MTC), pheochromocytoma (PCC), and/or primary hyperparathyroidism (PHPT) is related to the respective pathogenic variant of the RET proto-oncogene. The aim of this study is to retrospectively analyze the individual, genotype-dependent clinical manifestations of a large cohort of MEN2 patients. By comparing their clinical profile with currently existing evidence-based knowledge, an optimal therapy and prevention strategy in terms of prophylactic thyroidectomy and clinical follow-up could be ensured. This is a retrospective single-center study of 158 MEN2 patients who were diagnosed and/or surgically treated at a tertiary referral care center between 1990 and 2022. All participants were categorized according to their pathogenic variant of the RET proto-oncogene. Subsequently, the clinical manifestation of the disease and its time of occurrence was documented. Our analysis showed results in line with existing studies, except for a considerably lower-than-predicted occurrence of PCC in patients with V804M/L mutations. This study supports the current recommendation regarding the pathogenic variant-dependent management of this rare cancer-associated syndrome.

Thyroid Carcinoma, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology

Differentiated thyroid carcinomas is associated with an excellent prognosis. The treatment of choice for differentiated thyroid carcinoma is surgery, followed by radioactive iodine ablation (iodine-131) in select patients and thyroxine therapy in most patients. Surgery is also the main treatment for medullary thyroid carcinoma, and kinase inhibitors may be appropriate for select patients with recurrent or persistent disease that is not resectable. Anaplastic thyroid carcinoma is almost uniformly lethal, and iodine-131 imaging and radioactive iodine cannot be used. When systemic therapy is indicated, targeted therapy options are preferred. This article describes NCCN recommendations regarding management of medullary thyroid carcinoma and anaplastic thyroid carcinoma, and surgical management of differentiated thyroid carcinoma (papillary, follicular, Hürthle cell carcinoma).

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.

Long-term follow-up of RET Y791F carriers in Denmark 1994-2017: A National Cohort Study

BACKGROUND AND OBJECTIVES

Recently, a comprehensive study presented evidence that a long-disputed REarranged during Transfection (RET) variant, RET Y791F, should be classified as nonpathogenic. In spite of this, several subsequently published papers, including the revised American Thyroid Association guidelines for medullary thyroid carcinoma, refer to the variant as pathogenic. This study presents data from a unique national Danish cohort of RET Y791F carriers who have been followed by watchful waiting instead of being subjected to early thyroidectomy, to determine if any carrier shows evidence of multiple endocrine neoplasia 2A (MEN2A) at long-term follow-up.

METHODS

A national cohort of all patients tested for RET mutations in Denmark from September 1994 to October 2017 was searched for carriers of RET Y791F. Medical records and laboratory reports of carriers were reviewed for signs of MEN2A at latest follow-up (medullary thyroid carcinoma, primary hyperparathyroidism, pheochromocytoma, cutaneous lichen amyloidosis, or Hirschsprung's disease).

RESULTS

In total, twenty RET Y791F-carriers were identified, none of whom showed any evidence of MEN2A, despite an age range from 7 to 87 years.

CONCLUSIONS

Our national cohort study of all Danish RET Y791F carriers substantiates the claim that the RET Y791F variant is nonpathogenic.

Risk Profile of the RET A883F Germline Mutation: An International Collaborative Study

CONTEXT

The A883F germline mutation of the rearranged during transfection (RET) proto-oncogene causes multiple endocrine neoplasia 2B. In the revised American Thyroid Association (ATA) guidelines for the management of medullary thyroid carcinoma (MTC), the A883F mutation has been reclassified from the highest to the high-risk level, although no well-defined risk profile for this mutation exists.

OBJECTIVE

To create a risk profile for the A883F mutation for appropriate classification among the ATA risk levels.

DESIGN

Retrospective analysis.

SETTING

International collaboration.

PATIENTS

Included were 13 A883F carriers.

INTERVENTION

The intervention was thyroidectomy.

MAIN OUTCOME MEASURES

Earliest age of MTC, regional lymph node metastases, distant metastases, age-related penetrance of MTC and pheochromocytoma (PHEO), overall and disease-specific survival, and biochemical cure rate.

RESULTS

One and three carriers were diagnosed at age 7 to 9 years (median, 7.5 years) with a normal thyroid and C-cell hyperplasia, respectively. Nine carriers were diagnosed with MTC at age 10 to 39 years (median, 19 years). The earliest age of MTC, regional lymph node metastasis, and distant metastasis was 10, 20, and 20 years, respectively. Fifty percent penetrance of MTC and PHEO was achieved by age 19 and 34 years, respectively. Five- and 10-year survival rates (both overall and disease specific) were 88% and 88%, respectively. Biochemical cure for MTC at latest follow-up was achieved in 63% (five of eight carriers) with pertinent data.

CONCLUSIONS

MTC of A883F carriers seems to have a more indolent natural course compared with that of M918T carriers. Our results support the classification of the A883F mutation in the ATA high-risk level.

Surgical approaches in hereditary endocrine tumors

Endocrine tumors of thyroid, adrenal and parathyroid glands may be due to germline and inheritable mutations in 5-30% of patients. Medullary Thyroid Carcinoma, Pheochromocytoma, Paraganglioma, and Familial Primary Hyperparathyroidism are the most frequent entity. Hereditary endocrine tumors usually have a suggestive familial history; they occur earlier than sporadic variants, are multifocal, and have increased recurrence rates. They may be present as isolated variant or associated to other neoplasms in a syndromic setting. Genetic diagnosis should be preferably available before surgery because specific and targeted operative management are needed to achieve the best chance of cure. This review was aimed to discuss the surgical approaches for some of the most frequent hereditary endocrine tumors of thyroid, adrenal and parathyroid glands, focusing on medullary thyroid carcinoma, Pheochromocytoma, Paraganglioma and hereditary primary hyperparathyroidism (pHPT). Hereditary Medullary Thyroid Carcinoma is caused by RET mutations, and may be associated to Pheochromocytomas in MEN 2 setting. Total thyroidectomy and at least central neck nodal dissection is required. The availability of genetic screening allows prophylactic or early surgery in asymptomatic patients, with subsequent definitive cure. Hereditary Pheochromocytomas may be present in several syndromes (MEN 2, VHL, NF1, Paraganglioma/Pheochromocytoma syndrome); it may involve both adrenals; in these cases, a cortical sparing adrenalectomy should be performed to avoid permanent hypocorticosurrenalism. Hereditary Primary Hyperparathyroidism may frequently occur associated to MEN 1, MEN 2A, MEN 4, Hyperparathyroidism-Jaw Tumor Syndrome; it may involve all the parathyroid glands, requiring subtotal parathyroidectomy or total parathyroidectomy plus autotransplantation. In some cases, a selective parathyroidectomy might be performed.

The RET E616Q Variant is a Gain of Function Mutation Present in a Family with Features of Multiple Endocrine Neoplasia 2A

The REarranged during Transfection (RET) proto-oncogene is a receptor tyrosine kinase involved in growth and differentiation during embryogenesis and maintenance of the urogenital and nervous systems in mammals. Distinct mutations across hotspot RET exons can cause Multiple Endocrine Neoplasia Type 2A (MEN2A) characterised by development of medullary thyroid cancer (MTC), phaeochromocytoma (PCC) and primary hyperparathyroidism (PHPT), with a strong correlation between genotype and phenotype. Here, we report a 42-year-old man presented in the clinic with a unilateral PCC, with subsequent investigations revealing a nodular and cystic thyroid gland. He proceeded to thyroidectomy, which showed bilateral C-cell hyperplasia (CCH) without evidence of MTC. His brother had neonatal Hirschsprung disease (HSCR). Genetic testing revealed the presence of a heterozygous variant of unknown significance (VUS) in the cysteine-rich region of exon 10 in the RET gene (c.1846G>C, p.E616Q), in both affected siblings and their unaffected mother. Exon 10 RET mutations are known to be associated with HSCR and MEN2. Variants in the cysteine-rich region of the RET gene, outside of the key cysteine residues, may contribute to the development of MEN2 in a less aggressive manner, with a lower penetrance of MTC. Currently, a VUS in RET cannot be used to inform clinical management and direct future care. Analysis of RET^E616Q reveals a gain of function mutant phenotype for this variant, which has not previously been reported, indicating that this VUS should be considered at risk for future clinical management.

Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma

INTRODUCTION

The American Thyroid Association appointed a Task Force of experts to revise the original Medullary Thyroid Carcinoma: Management Guidelines of the American Thyroid Association.

METHODS

The Task Force identified relevant articles using a systematic PubMed search, supplemented with additional published materials, and then created evidence-based recommendations, which were set in categories using criteria adapted from the United States Preventive Services Task Force Agency for Healthcare Research and Quality. The original guidelines provided abundant source material and an excellent organizational structure that served as the basis for the current revised document.

RESULTS

The revised guidelines are focused primarily on the diagnosis and treatment of patients with sporadic medullary thyroid carcinoma (MTC) and hereditary MTC.

CONCLUSIONS

The Task Force developed 67 evidence-based recommendations to assist clinicians in the care of patients with MTC. The Task Force considers the recommendations to represent current, rational, and optimal medical practice.

Interest of sentinel node biopsy in apparently intrathyroidal medullary thyroid cancer: a pilot study

PURPOSE

Initial surgery for medullary thyroid cancer (MTC) with no evidence of lymph node involvement in neck compartments consists of total thyroidectomy and prophylactic central neck dissection. This study evaluated the reliability of a radiotracer technique for the intraoperative detection of sentinel lymph nodes (SLNs) in lateral compartments in patients with early MTC.

METHODS

Patients with limited (cT1 N0) MTC entered the study (2009-2012). A 0.1-0.3 ml suspension of macrocolloidal technetium-99-labeled human albumin was injected (under echo-guide) in the tumor 5 h before surgery. Preoperative lymphoscintigraphy confirmed the identification of SLNs in the lateral neck. The operation consisted of total thyroidectomy and central neck dissection, and a hand-held gamma-probe (Neoprobe) guide was used to remove the SLNs from the lateral neck.

RESULTS

Four patients were recruited. The tracer always indicated a SLN. Pathology reports indicated micrometastases from MTC in SLN in three patients. At a mean follow-up of 30.5 months, all patients were biochemically cured. The technique we describe to detect and remove neck SLN from MTC seemed to be very accurate. It always showed the SLNs (usually two) in the lateral compartments. Micrometastases were detected in three of four patients, allowing their correct staging.

CONCLUSIONS

The method described here for the detection of SLNs in early MTC seems effective and reliable and can be used for a more precise N staging of the patients. It could play a role, alone or combined with other techniques, in driving the extent of prophylactic neck dissection or other potential applications.

RET mutations in a large indian family with medullary thyroid carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) is a tumor arising from the para follicular (C) cells of the thyroid gland and can occur either sporadically or as part of an inherited syndrome. A proportion of these cases carry an autosomal dominant mutation in the RET (REarranged during Transfection) proto-oncogene. Screening for these mutations in the affected patients and the carriers "at risk" which includes the first-degree relatives is of utmost importance for early detection and prompt treatment including prophylactic thyroidectomy in cases that harbor these mutations.

RESULTS

This report presents details of screening and subsequent follow-up of a large Indian family, where the index case was found to carry p. Cys634Ser mutation involving exon 11 of the RET gene. These data are of value considering the paucity of information within the region in context of screening large families affected by these mutations.

Hereditary Pheochromocytoma

INTRODUCTION

Pheochromocytomas (PHEO) and paragangliomas (PGL) are rare neuroendocrine tumors with an estimated occurrence of 2 to 5 patients per million per year and an incidence of about 1 per 100 000 in the general population. These tumors may arise sporadically or be associated to various syndromes, namely multiple endocrine neoplasia type 2, neurofibromatosis type 1, Von Hippel-Lindau syndrome, and hereditary paraganglioma-pheochromocytoma syndromes.

OBJECTIVES

This article aims to review the current epidemiology, pathogenesis, clinical presentation, and genetic aspects of syndromes associated with hereditary PHEO/PGL.

METHODS

The literature research, conducted at PubMed database, included review articles, published from February 2009 to February 2014, written in English or Portuguese, using as query: "Hereditary AND Pheochromocytoma."

CONCLUSION

These tumors can be part of a myriad hereditary conditions that are not yet fully understood. Nevertheless, important systemic symptoms and even fatal outcomes can occur. Knowledge of these hereditary conditions can ensure a more efficient detection, treatment, and even prevention of these neuroectodermal tumors, thus new tests and studies should be conducted.

Pheochromocytoma as the first manifestation of MEN2A with RET mutation S891A: report of a case

We report a rare case with pheochromocytoma as the first manifestation of multiple endocrine neoplasia type 2A with RET mutation S891A. Bilateral pheochromocytomas were identified in a 54-year-old woman. Screening for RET revealed a rare S891A mutation located in the intracellular tyrosine kinase domain. This mutation was previously recognized as one of the mutations only in cases manifesting solely medullary thyroid carcinomas (MTCs). Since calcitonin stimulation test indicated positive result, total thyroidectomy was performed 1 year after the bilateral adrenalectomy, and C-cell hyperplasia was diagnosed by histopathological examination. Our report suggests that cases with S891A mutation, akin to those with other RET mutations, require screening for pheochromocytoma. In addition, it is indicated that calcitonin stimulation test should be performed even in the unaffected elder cases with S891A mutation although the mutation is classified as lowest risk group on MTC in guidelines.

The rare intracellular RET mutation p.Ser891Ala in an apparently sporadic medullary thyroid carcinoma: a case report and review of the literature

Medullary thyroid carcinoma (MTC) is a malignant tumor originating from parafollicular C-cells and accounts for 4-10% of all thyroid carcinomas. MTC develops in either sporadic (75%) or hereditary form (25%). Mutations in the RET proto-oncogene are responsible for hereditary MTC and the rate of heritable disease among apparently sporadic MTC (sMTC) cases varies from 6 to 15%. RET genetic testing is now considered fundamental in MTC management but the extent of the molecular analysis required to exclude inherited disease is still controversial. While the screening of all known mutation loci is recommended by some authors, the high costs associated with a full analysis should be also taken into consideration. Here, we illustrate and discuss this controversial issue by reporting a patient who present all characteristic features of sMTC, and in whom a standard genetic analysis by restriction enzyme restriction excluded hereditary disease. Nevertheless, an extensive molecular analysis that included all codons was prompted by the diagnosis of thyroid neoplasm in a patient's sister, and identified the rare intracellular RET p.Ser891Ala mutation.

New developments in the diagnosis and treatment of thyroid cancer

Thyroid cancer exists in several forms. Differentiated thyroid cancers include those with papillary and follicular histologies. These tumors exist along a spectrum of differentiation, and their incidence continues to climb. A number of advances in the diagnosis and treatment of differentiated thyroid cancers now exist. These include molecular diagnostics and more advanced strategies for risk stratification. Medullary cancer arises from the parafollicular cells and not the follicular cells. Therefore, diagnosis and treatment differs from those of differentiated thyroid tumors. Genetic testing and newer adjuvant therapies have changed the diagnosis and treatment of medullary thyroid cancer. This review will focus on the epidemiology, diagnosis, workup, and treatment of both differentiated and medullary thyroid cancers, focusing specifically on newer developments in the field.

The clinical spectrum of RET proto-oncogene mutations in codon 790

OBJECTIVE

Due to a strong genotype-phenotype correlation, the timing of prophylactic thyroidectomy in rearranged during transfection (RET) gene mutation carriers is usually dictated by genetic analysis.

SUBJECTS AND METHODS

We report a nationwide retrospective study of the clinical data of 77 French patients from 19 families with a mutation in codon 790 of the RET proto-oncogene.

RESULTS

The average age at diagnosis was 35.6 years ± 20.5. Thirty-nine patients were women. Fifty-five patients underwent operations for the treatment of medullary thyroid carcinoma (MTC) at the mean age of 38 years (4-82 years). The mean follow-up duration was 89 months. TNM staging was as follows: T0NxMx in 19, TxNxMx in 1, T1NxMx in 22, T1N1Mx in 8, T2N1Mx in 1 and T3N1Mx in four patients. In the T1/x-Nx group, 96% were considered cured after surgery. In the N1 group (n=13), six patients had multifocal disease and five patients were cured. Age and gender were not significant predictors of remission. Twenty-two patients did not undergo an operation (age 1.5-78 years); among them, 11 patients had a mean basal calcitonin (CT) level of 9.8 pg/ml (2-24) after 53 months of follow-up. One patient had been operated on for phaeochromocytoma (PHEO), and their CT level remained normal for 262 months.

CONCLUSIONS

This study confirms that RET 790 mutation is associated with a non-aggressive form of multiple endocrine neoplasia type 2, as 28% of the patients were followed up without thyroidectomy, 25% had been thyroidectomised with no tumour being detected and even patients with MTC had slow-evolving disease. Moreover, only one patient had PHEO, and no-one had primary hyperparathyroidism.

An unusual presentation of MEN2A

A 35-year-old woman presented with non-specific symptoms of fatigue and weight loss. Radiological investigations diagnosed a metastatic process and large bilateral adrenal masses. Histology from a liver biopsy and skin biopsy confirmed a diagnosis of metastatic medullary thyroid cancer. Further biochemical investigations revealed a positive 24-h urinary metanephrine collection and evidence of primary hyperparathyroidism. Genetic testing confirmed a mutant RET oncogene, confirming our clinical suspicion of multiple endocrine neoplasia type 2 (MEN2A) syndrome. The patient had no family history of endocrine disease and presented with widespread metastatic disease, making this an unusual presentation of MEN2A syndrome. Furthermore cutaneous metastases are rarely encountered in conjunction with metastatic medullary thyroid cancer. This case draws attention to the importance of genetic counselling in first-degree relatives of patients with confirmed MEN2A. This allows for timely diagnosis and reduced morbidity and mortality.

Pediatric thyroid disease: when is surgery necessary, and who should be operating on our children?

Surgical diseases of the thyroid in the pediatric population represent a diverse set of both benign and malignant conditions. Overall, incidence is rare. Benign conditions include Graves' disease, toxic adenomas, congenital hyperthyroidism, and goiter. Differentiated thyroid cancer (DTC) and medullary thyroid carcinoma (MTC), with its related familial cancer syndromes, are the most common malignancies. Near-total or total thyroidectomy is the appropriate surgery for thyroid cancer, with/out central lymph node dissection. Emerging practice guidelines from professional societies are helpful, although they generally have not addressed surgical management of the pediatric patient. Thyroidectomy in children is associated with a higher rate of complications, such as recurrent laryngeal nerve injury and hypoparathyroidism, as compared to the surgery in adults. Therefore, it is essential that pediatric thyroidectomy be performed by high-volume thyroid surgeons, regardless of specialty. Case volume to support surgical expertise usually must be borrowed from the adult experience, given the relative paucity of pediatric thyroidectomies at an institutional level. These surgeons should work as part of a multidisciplinary team that includes pediatric endocrinologists and anesthesiologists, pediatricians, nuclear medicine physicians, and pathologists to afford children the best clinical outcomes.

Is basal ultrasensitive measurement of calcitonin capable of substituting for the pentagastrin-stimulation test?

OBJECTIVE

To evaluate a second-generation assay for basal serum calcitonin (CT) measurements compared with the pentagastrin-stimulation test for the diagnosis of inherited medullary thyroid carcinoma (MTC) and the follow-up of patients with MTC after surgery. Recent American Thyroid Association recommendations suggest the use of basal CT alone to diagnose and assess follow-up of MTC as the pentagastrin (Pg) test is unavailable in many countries.

DESIGN

Multicentric prospective study.

PATIENTS

A total of 162 patients with basal CT <10 ng/l were included: 54 asymptomatic patients harboured noncysteine 'rearranged during transfection' (RET) proto-oncogene mutations and 108 patients had entered follow-up of MTC after surgery.

MEASUREMENT

All patients underwent basal and Pg-stimulated CT measurements using a second-generation assay with 5-ng/l functional sensitivity.

RESULTS

Ninety-five per cent of patients with basal CT ≥ 5 ng/l and 25% of patients with basal CT <5 ng/l had a positive Pg-stimulation test (Pg CT >10 ng/l). Compared with the reference Pg test, basal CT ≥ 5 ng/l had 99% specificity, a 95%-positive predictive value but only 35% sensitivity (P < 0.0001). Overall, there were 31% less false-negative results using a 5-ng/l threshold for basal CT instead of the previously used 10-ng/l threshold.

CONCLUSION

The ultrasensitive CT assay reduces the false-negative rate of basal CT measurements when diagnosing familial MTC and in postoperative follow-up compared with previously used assays. However, its sensitivity to detect C-cell disease remains lower than that of the Pg-stimulation test.

RET codon 609 mutations: a contribution for better clinical managing

Medullary thyroid carcinoma currently accounts for 5-8% of all thyroid cancers. The clinical course of this disease varies from extremely indolent tumors that can go unchanged for years to an extremely aggressive variant that is associated with a high mortality rate. As many as 75% of all medullary thyroid carcinomas are sporadic, with an average age at presentation reported as 60 years, and the remaining 25% are hereditary with an earlier age of presentation, ranging from 20 to 40 years. Germline RET proto-oncogene mutations are the genetic causes of multiple endocrine neoplasia type 2 and a strong genotype-phenotype correlation exists, particularly between a specific RET codon mutation and the (a) age-related onset and (b) thyroid tumor progression, from C-cell hyperplasia to medullary thyroid carcinoma and, ultimately, to nodal metastases. RET mutations predispose an individual to the development of medullary thyroid carcinomas and can also influence the individual response to RET protein receptor-targeted therapies. RET codon 609 point mutations are rare genetic events belonging to the intermediate risk category for the onset of medullary thyroid carcinoma. A large genealogy resulting in a less aggressive form of medullary thyroid carcinoma is associated with the high penetrance of pheochromocytoma and has been reported in the literature. In this short review article, we comment on our previous report of a large multiple endocrine neoplasia type 2A kindred with the same Cys609Ser germline RET mutation in which, conversely, the syndrome was characterized by a slightly aggressive, highly penetrant form of medullary thyroid carcinoma that was associated with low penetrance of pheochromocytoma and primary hyperparathyroidism.

Genetics of pheochromocytomas and paragangliomas

Pheochromocytoma and paraganglioma are tumors of the sympathetic or parasympathetic paraganglia. Pheochromocytoma is the tumor of the main sympathetic paraganglia, which is the adrenal medulla. The sympathetic paraganglioma secretes catecholamine while the parasympathetic do not. Both of them originate from neural crest cells and share similar mechanisms of tumor development. The same genetic alteration may predispose to the development of sympathetic and parasympathetic paraganglioma. The best known hereditary forms of pheochromocytoma and paraganglioma are the von Hippel-Lindau disease, in which pheochromocytoma may be associated with CNS hemangioblastoma, retinal angioma, pancreatic endocrine tumor/cysts and renal clear cell carcinoma/cysts; the multiple endocrine neoplasia type 2, in which pheochromocytoma is associated with medullary thyroid carcinoma and primary hyperparathyroidism, Type 1 neurofibromatosis, the most frequent hereditary cancer syndrome. Finally, it has been characterized the paraganglioma syndrome in which sympathetic and parasympathetic paraganglioma are variously associated. The list of predisposing gene is quite long and comprises VHL, RET, NF1, SDHB, SDHC, SDHD, SDHAF2. More rarely, two other genes may predispose to pheochromocytoma/paraganglioma development: KIF1Bbeta and PHD2. A mechanism conducing to a defective apoptosis is the common pathways of those genes. Finally, there is also good evidence of the role of other genes, not yet completely identified.

Medullary thyroid carcinoma: long-term outcomes of surgical treatment

BACKGROUND

Medullary thyroid carcinoma (MTC) accounts for 5 to 10% of all thyroid cancers but is responsible for a disproportionate number of deaths.

METHODS

We performed a retrospective review to describe clinical outcomes in patients with medullary thyroid carcinoma, screening a subset of patients for somatic mutations in the RET and p18 genes and performing genotype-phenotype correlation in a tertiary-care referral hospital from 1967 to 2009.

RESULTS

We studied a total of 94 patients identified from a prospectively maintained thyroid cancer database. Data gathered included patient demographics, serum calcitonin, clinical outcomes, histopathology, genetic analysis, and status at final follow-up. A subset cohort (n = 50) was screened for somatic mutations in the RET gene and the three exons of the p18 gene. The subset cohort was composed of hereditary medullary thyroid carcinoma (HMTC) (n = 19, index patients = 10, screen detected = 9) and sporadic medullary thyroid carcinoma (SMTC) (n = 31). There were no mutations in the p18 gene in the subset cohort.

CONCLUSIONS

A total of 67 SMTC and 27 (28.7%) HMTC cases identified. SMTC were older at initial presentation (52 vs. 34, P = 0.003), had higher preoperative serum calcitonin levels (7968 vs. 1346 ng/L, P = 0.008), and had lymph node recurrence (P = 0.001) compared to HMTC. The tumors were smaller in HMTC (P = 0.038). Overall 10-year survival in SMTC versus HMTC was 69 versus 93% (P = 0.12). On multivariate analysis, vascular invasion (hazard ratio 6.4, P = 0.019) was an adverse predictor for disease-free survival. HMTC in the era of RET analysis presents with a smaller primary tumor, lower preoperative serum calcitonin levels, and lower rates of lymph node metastasis. Mutations in the p18 gene were not a major factor in medullary thyroid carcinoma tumorigenesis.

Factors predicting outcome of total thyroidectomy in young patients with multiple endocrine neoplasia type 2: a nationwide long-term follow-up study

Background

Multiple endocrine neoplasia type 2 (MEN 2) is caused by a RET mutation in chromosome 10. All MEN 2 patients develop medullary thyroid carcinoma (MTC). The age-related risk of MTC is associated with the type of RET mutation. Our aim was to identify prognostic factors associated with recurrent MTC in MEN 2 patients.

Methods

In a nationwide case–control study, all patients who underwent total thyroidectomy in the Netherlands under the age of 20 years were classified into standard (1), high (2), or very high risk (3) for MTC based on RET-mutation type. Disease-free patients were compared with those with recurrent disease.

Results

A total of 93 patients were included in the study. Sixty-six percent had MTC on histology, the youngest being 1 year old. Codon 634 was most affected. Sixteen (18%) patients had persistent or recurrent disease, one of whom died. Significantly associated determinants of outcome in univariate analysis were higher age at surgery, no age-appropriate prophylactic surgery according to risk level, elevated preoperative calcitonin levels, affected codon, and the presence of lymph node metastases at surgery. On multivariate analysis only age of surgery was the single independent factor associated with persistent disease.

Conclusions

Prophylactic thyroidectomy beyond the recommended age is associated with persistent/recurrent disease. In addition, codon 634 mutation is associated with a high risk of recurrence requiring early surgery for all these patients.

[Surgery of thyroid carcinoma]

The 5 main types of thyroid cancer (papillary, PTC, follicular, FTC, poorly differentiated, PDTC undifferentiated, UTC, medullary, MTC) not only differ regarding morphology, pathogenesis, genetics,and pathophysiology (iodine metabolism, thyroglobulin and calcitonin production), but also concerning tumor biology, metastatic behavior (lymphogenous, locally invasive and hematogenous routes) and prognosis. Knowledge of these features is the basis of the surgical concept of one or two-stage thyroidectomy, the exceptions and the concept of locoregional lymph node dissection. Lymph node surgery plays an important role in those cancers exhibiting mainly lymph node metastases (PTC, MTC) not only due to frequent recurrences but also due to its potential curative intent. Differentiated carcinomas may have an acceptable prognosis despite local invasion of the cervical aerodigestive system, thus resections are justified when technical prerequisites are given.

A Korean family of familial medullary thyroid cancer with Cys618Ser RET germline mutation

Familial medullary thyroid carcinoma (FMTC) is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene. An identifiable RET mutation can be detected in about 85% of FMTC families. The majority of germline mutations in FMTC have been found in exons 10 and 11 of the RET proto-oncogene, specifically within the cysteine codons 609, 611, 618, 620, and 634. We screened members of a large Korean family that had a history of FMTC by genetic analyses, and propose a therapeutic approach for managing the disorder. We report a RET mutation in exon10, codon 618 that causes substitution of a cysteine by a serine in the cysteine-rich domain of the RET receptor in a three-generation FMTC family composed of 30 members with 11 carriers. Nine of the gene carriers were clinically affected. The FMTC with cysteine RET mutations found in the Korean population is consistent with the clinical pattern reported worldwide; to date there have been no ethnic differences identified for FMTC. Our results suggest that this genetic profile might be associated with usually aggressive clinical course with regional lymph node metastasis but late onset of MTC.

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.

RET mutation Tyr791Phe: the genetic cause of different diseases derived from neural crest

Activating germline RET mutations are presented in patients with familial medullary thyroid carcinoma (FMTC) and multiple endocrine neoplasia (MEN) types 2A and 2B, whereas inactivating germline mutations in patients with Hirschsprung's disease (HSCR). The aim of this study was to evaluate genotype-phenotype correlations of the frequently discussed Tyr791Phe mutation in exon 13 of the RET proto-oncogene. Screening of three groups of patients was performed (276 families with medullary thyroid carcinoma (MTC), 122 families with HSCR, and 29 patients with pheochromocytoma). We found this mutation in 3 families with apparently sporadic MTC, 3 families with FMTC/MEN2, 1 patient with pheochromocytoma, and 3 families with HSCR. All gene mutation carriers have a silent polymorphism Leu769Leu in exon 13. In three families second germline mutations were detected: Cys620Phe (exon 10) in MEN2A family, Met918Thr (exon 16) in MEN2B family, and Ser649Leu (exon 11) in HSCR patient. Detection of the Tyr791Phe mutation in MEN2/MTC and also in HSCR families leads to the question whether this mutation has a dual character (gain-of-function as well as loss-of-function). A rare case of malignant pheochromocytoma in a patient with the Tyr791Phe mutation is presented. This study shows various clinical characteristics of the frequently discussed Tyr791Phe mutation.

Targeting the RET pathway in thyroid cancer

The RET (rearranged during transfection) protooncogene encodes a single pass transmembrane receptor that is expressed in cells derived from the neural crest and the urogenital tract. As part of a cell-surface complex, RET binds glial derived neurotrophic factor (GDNF) ligands in conjunction with GDNF-family alpha co-receptors (GFRalpha). Ligand-induced activation induces dimerization and tyrosine phosphorylation of the RET receptor with downstream activation of several signal transduction pathways. Activating germline RET mutations play a central role in the development of the multiple endocrine neoplasia (MEN) syndromes MEN2A, MEN2B, and familial medullary thyroid carcinoma (FMTC) and also in the development of the congenital abnormality Hirschsprung's disease. Approximately 50% of patients with sporadic MTC have somatic RET mutations, and a significant portion of papillary thyroid carcinomas result from chromosomal inversions or translocations, which activate RET (RET/PTC oncogenes). The RET protooncogene has a significant place in cancer prevention and treatment. Timely thyroidectomy in kindred members who have inherited a mutated RET allele, characteristic of MEN2A, MEN2B, or FMTC, can prevent MTC, the most common cause of death in these syndromes. Also, recently developed molecular therapeutics that target the RET pathway have shown activity in clinical trials of patients with advanced MTC, a disease for which there has been no effective therapy.

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.

Multiple endocrine neoplasia type 2 RET protooncogene database: repository of MEN2-associated RET sequence variation and reference for genotype/phenotype correlations

Multiple endocrine neoplasia type 2 (MEN2) is an inherited, autosomal-dominant disorder caused by deleterious mutations within the RET protooncogene. MEN2 RET mutations are mainly heterozygous, missense sequence changes found in RET exons 10, 11, and 13-16. Our group has developed the publicly available, searchable MEN2 RET database to aid in genotype/phenotype correlations, using Human Genome Variation Society recommendations for sequence variation nomenclature and database content. The MEN2 RET database catalogs all RET sequence variation relevant to the MEN2 syndromes, with associated clinical information. Each database entry lists a RET sequence variation's location within the RET gene, genotype, pathogenicity classification, MEN2 phenotype, first literature reference, and comments (which may contain information on other clinical features, complex genotypes, and additional literature references). The MEN2 phenotype definitions were derived from the International RET Mutation Consortium guidelines for classification of MEN2 disease phenotypes. Although nearly all of the 132 RET sequence variation entries initially cataloged in the database were from literature reports, novel sequence variation and updated phenotypic information for any existing database entry can be submitted electronically on the database website. The database website also contains links to selected MEN2 literature reviews, gene and protein information, and RET reference sequences. The MEN2 RET database (www.arup.utah.edu/database/MEN2/MEN2_welcome.php) will serve as a repository for MEN2-associated RET sequence variation and reference for RET genotype/MEN2 phenotype correlations.

Medullary thyroid carcinoma and biomarkers: past, present and future

The clinical management of patients with persistent or recurrent medullary thyroid carcinoma (MTC) is still under debate, because these patients either have a long-term survival, due to an indolent course of the disease, or develop rapidly progressing disease leading to death from distant metastases. At this moment, it cannot be predicted what will happen within most individual cases. Biomarkers, indicators which can be measured objectively, can be helpful in MTC diagnosis, molecular imaging and treatment, and/or identification of MTC progression. Several MTC biomarkers are already implemented in the daily management of MTC patients. More research is being aimed at the improvement of molecular imaging techniques and the development of molecular systemic therapies. Recent discoveries, like the prognostic value of plasma calcitonin and carcino-embryonic antigen doubling-time and the presence of somatic RET mutations in MTC tissue, may be useful tools in clinical decision making in the future. In this review, we provide an overview of different MTC biomarkers and their applications in the clinical management of MTC patients.

Constitutive RET tyrosine kinase activation in hereditary medullary thyroid cancer: clinical opportunities

The ground-breaking discovery of genotype-phenotype relationships in hereditary medullary thyroid cancer has greatly facilitated early prophylactic thyroidectomy. Its timing depends not solely on a positive gene test but, more importantly, on the type of the REarranged during Transfection (RET) mutation and its underlying mode of RET receptor tyrosine kinase activation. In the past decade, the therapeutic corridor opened by molecular information has been defined down to a remarkable level of detail. Based on mutational risk profiles, preemptive thyroidectomy is recommended at 6 months of age for carriers of highest-risk mutations, before the age of 5 years for carriers of high-risk mutations, and before the age of 5 or 10 years for carriers of least-high-risk mutations. Additional lymph node dissection may not be needed in the absence of increased preoperative basal calcitonin levels. Better comprehension of RET function should enable the design of targeted therapies for RET carriers beyond surgical cure in whom the DNA-based 'window of opportunity' has been missed.

Determination of calcitonin levels in C-cell disease: clinical interest and potential pitfalls

An elevated serum calcitonin level is a highly sensitive marker for medullary thyroid carcinoma (MTC) that can be used for screening, differential diagnosis, prognostic assessment, follow-up monitoring, and assessment of treatment response. Nevertheless, additional data are required to definitively support routine measurement of calcitonin levels in the initial work-up of patients with thyroid nodules, mainly because there is no convincing evidence that such testing actually reduces MTC-related mortality. By contrast, the prognostic value of measuring calcitonin levels preoperatively, postoperatively, and during follow-up of patients with MTC is widely acknowledged. Furthermore, determination of calcitonin levels is also used to evaluate the response of MTC to novel forms of systemic treatment, such as tyrosine kinase inhibitors. In this Review, we discuss the key issues surrounding the use of this laboratory test in the clinical management of patients with MTC.

[Hereditary thyroid cancer]

Hereditary thyroid carcinomas are present in about 5% of differentiated (DTC) and 25% of medullary thyroid carcinomas (MTC). They are part of a multiorgan tumour syndrome (e. g. FAP Gardner's syndrome with DTC and MEN 2 syndrome with MTC) or confined to the thyroid gland. Hereditary thyroid carcinomas typically show multifocal growth and occur in young patients. Due to germ cell mutations as the underlying cause of disease, partial thyroidectomies that may be justified in early sporadic carcinomas are not indicated in this type of tumours. In the case of hereditary DTC, the genetic basis of the disease has been demonstrated only in syndromatic tumour variants. In most nonsyndromatic cases, specific genetic alterations have not yet been identified. In both types of hereditary DTC, prophylactic thyroidectomy is not warranted due to the favourable prognosis of tumours that do not differ from sporadic ones. Point mutations of the RET proto-oncogene have been known for 15 years to be the genetic basis of hereditary MTC. Recently several new mutations were discovered; however, final conclusions regarding their clinical significance are not possible at present. Basically it has been shown that the clinical aggressivity of tumour development follows a genotype-phenotype correlation (risk groups 1-3). However, in mutations of all risk classes there exists a wide spectrum of different stages of hereditary C-cell disease in individual risk groups. Regarding time and extent of prophylactic thyroidectomy (without or with lymph node dissection) a combined molecular-biochemical concept including the use of pentagastrin-stimulated calcitonin values is therefore recommended.

Safe incorporation of new technologies in thyroid surgery

The history of thyroid surgery starts with Billroth, Kocher and Halsted, who developed the technique for thyroidectomy between the years of 1873 and 1910. In general the essential objectives for thyroidectomy are: sparing the parathyroid glands, avoidance of injury to the laryngeal nerves, an accurate hemostasis and an excellent cosmesis. In the last 10 years, major improvements and new technologies have been proposed and applied in thyroid surgery. These include mini-invasive thyroidectomy, new devices for achieving hemostasis and dissection, regional anesthesia, intraoperative neuromonitoring, parathyroid hormone assay technology and genetic screening. This paper reviews the relevant medical literature published on the influence of these new technologies on the quality of thyroid surgery, as well as prevention of postoperative morbidity and mortality. Searches were last updated in April 2008.

Thyroid disorders: evaluation and management of thyroid nodules

Although thyroid nodules are a common clinical entity, few (5% to 10%) are malignant and require surgical treatment. Most nodules are discovered incidentally in patients undergoing surveillance for medical reasons unrelated to thyroid disorders. Therefore, a systematic approach to their evaluation is important to avoid unnecessary surgery. High-resolution ultrasonography and fine-needle aspiration have resulted in substantial improvements in diagnostic accuracy, cost reductions, and higher malignancy yield at the time of surgery. In this article, the authors present practical guidelines and a suggested management strategy for the effective diagnosis and management of incidentally discovered thyroid nodules.