Spontaneous and Treatment-Related Changes of Serum Calcitonin in Medullary Thyroid Cancer: Long-Term Experience in a Patient With Multiple Endocrine Neoplasia Type 2B

PURPOSE

Medullary thyroid carcinoma (MTC) in MEN2B syndrome is associated with germline RET mutation. Patients harboring de novo mutations are usually diagnosed at more advanced disease stages. We present a young woman with Met918Th mutation diagnosed with stage IV MTC at age 10 years.

METHODS

The disease progressed despite total thyroidectomy and multiple surgical interventions for cervical lymph node recurrences, leading to distant metastases in the fifth year after the initial diagnosis. Subsequently, she underwent five different types of tyrosine kinase inhibitor (TKI) treatments. The 17-year disease course was divided into periods defined by four surgical interventions and sequential treatment intervals with four multikinase (sunitinib, vandetanib, cabozantinib, and lenvatinib) and one RET-selective TKI (selpercatinib). Tumor growth for different phases of spontaneous development and drug treatment intervals was characterized by changes in serial log-transformed calcitonin measurements (n = 114).

RESULTS

Three operations (one for calcitonin-producing adrenal pheochromocytoma) were associated with drops in calcitonin levels. All of the nonselective TKIs were stopped due to adverse effects. As reflected by the negative calcitonin doubling rate, the best treatment response was observed with selpercatinib, which was associated with an initial large drop followed by a decreasing calcitonin trajectory over 514 days without any major side effects.

CONCLUSION

This case of MEN2B medullary thyroid cancer with long-term survival presents how the effectiveness of different treatment modalities can be estimated using log-transformed calcitonin levels. Furthermore, our experience supports the view that serial calcitonin measurements may be more sensitive than radiological follow-up in advanced MTC. Our patient also represents a new case of rarely reported calcitonin-producing pheochromocytomas.

Impact of Early Diagnostic and Therapeutic Interventions and Clinical Course in Children and Adolescents with Multiple Endocrine Neoplasia Types 1 and 2

PURPOSE

Multiple endocrine neoplasia types 1 (MEN1) and 2 (MEN2) are inherited endocrine tumor syndromes caused by mutations in the MEN1 or RET genes. This study aimed to investigate clinical outcomes and molecular characteristics among children with MEN.

METHODS

This study included eight patients from seven unrelated families. Data on clinical course, biochemical findings, and radiologic studies were collected by retrospective chart review. All diagnoses were genetically confirmed by Sanger sequencing of MEN1 in three MEN1 patients and RET in four patients with MEN2A and one patient with MEN2B.

RESULTS

Three patients with MEN1 from two families presented with hypoglycemia at a mean age of 11±2.6 years. Four patients with MEN2A were genetically diagnosed at a mean of 3.0±2.2 years of age by family screening; one of them was prenatally diagnosed by chorionic villus sampling. Three patients with MEN2A underwent prophylactic thyroidectomy from 5 to 6 years of age, whereas one patient refused surgery. The patient with MEN2B presented with a tongue neuroma and medullary thyroid carcinoma at 6 years of age. Subsequently, he underwent a subtotal colectomy because of bowel perforation and submucosal ganglioneuromatosis at 18 years of age.

CONCLUSION

This study described the relatively long clinical course of pediatric MEN with a mean follow-up duration of 7.5±3.8 years. Insulinoma was the first manifestation in children with MEN1. Early diagnosis by family screening during the asymptomatic period enabled early intervention. The patient with MEN2B exhibited the most aggressive clinical course.

Tumor-to-Tumor Metastasis of Medullary Thyroid Carcinoma to Paraganglioma in a Multiple Endocrine Neoplasia Type 2B Patient: A Case Report and Literature Review

Tumor-to-tumor metastasis is a rare phenomenon in which primary tumor cells metastasize to other tumors. Herein, we report an extremely rare case of tumor-to-tumor metastasis of medullary thyroid carcinoma to a paraganglioma in a patient with multiple endocrine neoplasia type 2B. Based on genetic examination, a 36-year-old woman was diagnosed with multiple endocrine neoplasia type 2B when she was 24 years old. She had a history of total thyroidectomy for medullary thyroid carcinoma and bilateral adrenalectomy for pheochromocytomas, which were performed when she was 15 years and 29 years old, respectively. Follow-up computed tomography demonstrated a retroperitoneal tumor of 30 mm in diameter beside the left kidney and a liver tumor of 16 mm in diameter located in segment 6. The retroperitoneal and liver tumors were surgically resected and examined by a pathologist. Histological examination revealed the classic Zellballen pattern in the retroperitoneal tumor, rendering the diagnosis of a paraganglioma recurrence. Inside the tumor, a white nodule positive for carcinoembryonic antigen, weakly positive for calcitonin, and negative for tyrosine hydroxylase, was identified and diagnosed as a metastatic medullary thyroid carcinoma with high malignant potential. The liver lesion was diagnosed as a metastasis of the medullary thyroid carcinoma. This is the first report of tumor-to-tumor metastasis of medullary thyroid carcinoma to paraganglioma in a patient with multiple endocrine neoplasia type 2B twenty years after total thyroidectomy.

[Intestinal ganglioneuromatosis as an early extra-endocrine manifestation of type 2B multiple endocrine neoplasia]

Multiple endocrine neoplasia type 2B (MEN 2B) is a rare variant of hereditary tumor syndromes caused by germinal mutations in the proto-oncogene RET. One of the components of the syndrome is multiple neurinomas, the early detection of  which is not always given due attention. We present a description of the case of MEN 2B, manifested in the first months of life by intestinal ganglioneuromatosis. The disease presented with chronic constipation, including episodes of intestinal obstruction that required repeated surgical interventions. MEN 2B was suspected at the age of 15. At the time of diagnosis, an increase in serum calcitonin levels was noted (1041 pg/ml, norm <9.5 pg/ml), and a node in the thyroid gland was also determined (1,3*1,0*1,2 see, TIRADS 5), subsequently verified as a neoplasm of C-cells. By DNA analysis, a pathogenic variant p.Met918Thr, typical for MEN2 B, was detected in the RET gene. No signs of pheochromocytoma were found at the time of investigation. The patient underwent a thyroidectomy with lymphadenectomy. The difficulties of early diagnosis of sporadic cases of MEN 2B due to the nonspecificity of gastrointestinal manifestations of the disease are discussed.

Fracture Risk in Pediatric Patients With MEN2B

CONTEXT

The skeletal phenotype of patients with MEN2B has been described but fracture risk in these patients has not yet been evaluated.

OBJECTIVE

This work aims to better delineate fracture risk in patients with multiple endocrine neoplasia type 2B (MEN2B).

METHODS

This case series with chart review was conducted at the National Institutes of Health, Pediatric Oncology Branch. A total of 48 patients with MEN2B were identified, with an age range of 5 to 36 years, median of 19; 24 of 48 (50%) patients were female. Medical records, demographic information, available imaging, and laboratory results were reviewed. History up to age 19 was included in the statistical analyses.

RESULTS

Of the 48 patients with MEN2B, 20 patients experienced at least one fracture. The majority (n = 18) experienced their first fracture at or before age 19. The observed frequency of fracture occurrence throughout childhood (0-19 years) was 38%, with very little difference between males and females. This frequency is higher than the 9.47 to 36.1 fractures per 1000 persons per year that has been reported in healthy pediatric cohorts in the United States. Less common sites of fracture including vertebral compression fracture and pelvic fractures were observed in patients with MEN2B.

CONCLUSION

In this group of patients with MEN2B, there was an increased overall risk of fracture compared to general pediatric cohorts in the United States. Less common sites of fracture were also observed. This suggests a possible effect of an activating RET mutation on bone physiology and warrants further investigation.

Timely diagnosis of multiple endocrine neoplasia 2B by identification of intestinal ganglioneuromatosis: a case series

BACKGROUND

Medullary thyroid carcinoma (MTC) in childhood is rare and has an unfavorable prognosis. To improve outcome, early diagnosis is essential. In patients with multiple endocrine neoplasia type 2B (MEN2B), MTC can occur already before the age of 1 year. Recognition of non-endocrine features of MEN2B may lead to timely diagnosis.

PURPOSE

To describe how early recognition of non-endocrine features can lead to a timely diagnosis of MEN2B as well as the effect of recognition of premonitory symptoms on prognosis.

METHODS

A retrospective case series from the University Medical Center Utrecht/Wilhelmina Children's Hospital, a Dutch national expertise center for MEN patients. All eight MEN2B patients in follow-up between 1976 and 2020 were included and medical records reviewed.

RESULTS

Intestinal ganglioneuromatosis (IGN) as the cause of gastrointestinal (GI) symptoms was detected in seven patients. In three of them within months after birth. This led to early diagnosis of MEN2B, which allowed subsequent curative thyroid surgery. On the contrary, a MEN2B diagnosis later in childhood-in three patients (also) triggered by oral neuromas/neurofibromas-led to recurrent, persistent, and/or progressive MTC in five patients.

CONCLUSIONS

Neonatal GI manifestations offer the most important window of opportunity for early detection of MEN2B. By accurate evaluation of rectal biopsies in patients with early onset severe constipation, IGN can be timely detected, while ruling out Hirschsprung's disease. MEN2B gene analysis should follow detection of IGN and-when confirmed-should prompt possibly still curative thyroid surgery.

A Novel Double RET E768D/L790F Mutation Associated with a MEN2B-Like Phenotype

Background: Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant disorder caused by mutations in the RET proto-oncogene. MEN2 is classified into two subtypes, MEN 2A and 2B. MEN2B is characterized by early-onset and aggressive medullary thyroid carcinoma (MTC), pheochromocytoma, and characteristic physical features. Patient Findings: We present a 39-year-old male with early-onset metastatic MTC diagnosed at the age of 13 years and physical features typical for MEN2B such as marfanoid habitus, mucosal neuromas, and thickened eyelids. The patient has two first-degree relatives (mother and maternal uncle) with MTC and pheochromocytoma. The mother has similar facial features. RET sequencing revealed a novel tandem RET E768D/L790F germline mutation in exon 13. The patient's mother has the same RET variant. For functional in vitro characterization, wild-type RET, RET E768D, RET L790F, the double RET E768D/L790F mutant, and RET M918T were expressed in HEK293 cells. The novel double RET E768D/L790F mutant increased ligand-independent RET phosphorylation, activation of the mitogen-activated protein kinase (MAPK)-pathway, and colony formation similar to the classical MEN2B RET M918T mutation. Summary: In this male patient with a MEN2B-like phenotype, we identified a novel double RET germline mutation, E768D/L790F. Functional characterization of the double mutant shows similar transforming capacity as RET M918T.

Multiple endocrine neoplasia-IIb with RET gene mutation p.M918T： A case report

Multiple endocrine neoplasia-IIb (MEN-IIb) is a rare hereditary autosomal dominant syndrome caused by mutations in the RET proto-oncogene. It's characterized by medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO), mucosal neuromas, and Marfanoid habitus. Because of the rarity of MEN-IIb and finiteness of clinical cognition, the majority of the patients suffer a delayed diagnosis. A MEN-IIb patient with the lingual mucosal neuromas since childhood was admitted in the Third Xiangya Hospital of Central South University in November, 2018. He had surgical history of mitral valve prolapse and spinal deformity. He was diagnosed with MTC and PHEO at the age of 22 and 28, respectively, and received surgical treatments. Sequencing of RET gene revealed a de novo heterozygous p.M918T mutation in the patient. Being aware of the unique clinical phenotype and screening of RET gene mutation may lead to the early diagnosis and better long-term outcome for MEN-IIb.

Update on Pheochromocytoma and Paraganglioma from the SSO Endocrine/Head and Neck Disease-Site Work Group. Part 1 of 2: Advances in Pathogenesis and Diagnosis of Pheochromocytoma and Paraganglioma

This first part of a two-part review of pheochromocytoma and paragangliomas (PPGLs) addresses clinical presentation, diagnosis, management, treatment, and outcomes. In this first part, the epidemiology, prevalence, genetic etiology, clinical presentation, and biochemical and radiologic workup are discussed. In particular, recent advances in the genetics underlying PPGLs and the recommendation for genetic testing of all patients with PPGL are emphasized. Finally, the newer imaging methods for evaluating of PPGLs are discussed and highlighted.

Genetic characterization of medullary thyroid cancer in childhood survivors of the Chernobyl accident

BACKGROUND

Radiation-associated fusion oncogenes play a direct role in papillary thyroid cancer development and pathogenic fusions have recently been reported in medullary thyroid cancer. To date, no studies have evaluated oncogenic events in medullary thyroid cancer in a radiation-exposed population.

METHODS

Somatic and germline alterations, including RET fusions, were evaluated in paired medullary thyroid cancer tumor and normal samples from the Chernobyl Tissue Bank, a heavily screened population affected by the Chernobyl disaster.

RESULTS

Tissue was available for 49 individuals. The median age of diagnosis was 26 years (range 9 to 43 years); 16 were radiation-exposed at a median age of 6 (range 2 days to 17 years). A total of 21 patients harbored germline RET mutations (codons 634[13], 918[5], 790[1], 609[1], and 620[1]); 4 had family history. Sporadic medullary thyroid cancer was identified in 27 patients (RET[18], KRAS[1], RET+KRAS[1], TP53[1], wild type [6]), with 1 RET fusion (1/49;2%). The age at operation for patients with hereditary medullary thyroid cancer was not different than sporadic medullary thyroid cancer (23.5 vs 28 years, P = .063). In sporadic medullary thyroid cancer, radiation was not associated with a difference in age at operation, tumor size, or tumor stage (P > .05).

CONCLUSION

In a heavily screened cohort, genetic analysis revealed germline RET mutations in previously unrecognized probands and a remarkable number of sporadic medullary thyroid cancer cases with a young age at presentation.

Pheochromocytoma in Children and Adolescents With Multiple Endocrine Neoplasia Type 2B

CONTEXT

Multiple endocrine neoplasia type 2B (MEN2B) is characterized by early-onset medullary thyroid cancer in virtually all cases and a 50% lifetime risk of pheochromocytoma (PHEO) development. The literature on PHEO in patients with MEN2B is limited with most data being reported from adult studies that primarily address MEN2A.

OBJECTIVE

The aim of the current study is to describe PHEO development in a cohort of pediatric patients with MEN2B.

DESIGN

Retrospective chart review of patients with MEN2B evaluated at the National Institutes of Health in the period between July 2007 and February 2018.

RESULTS

A total of 38 patients were identified (21 males and 17 females). Mean age at MEN2B diagnosis was 10.6 ± 3.9 years. Eight patients (21%) developed PHEO in the course of follow-up to date, all of whom were sporadic cases with the classic M918T RET mutation. PHEO was diagnosed based on biochemical and/or imaging screening studies in five patients, whereas three patients presented with symptoms of excess catecholamines. PHEO was diagnosed at a mean age 15.2 ± 4.6 (range, 10 to 25) years and 4.0 ± 3.3 years after MEN2B diagnosis. Only one patient was diagnosed with PHEO as the initial manifestation of MEN2B after she presented with hypertension and secondary amenorrhea.

CONCLUSION

Undiagnosed PHEO can be associated with substantial morbidity. Current American Thyroid Association guidelines recommend PHEO screening starting at age 11 for the high-/highest risk group. The youngest patient diagnosed with PHEO in our cohort was an asymptomatic 10-year-old, suggesting that PHEO development may begin before the screening-recommended age of 11, though remains clinically undetectable and thus the current screening guidelines seem appropriate.

A comprehensive review on MEN2B

MEN2B is a very rare autosomal dominant hereditary tumor syndrome associated with medullary thyroid carcinoma (MTC) in 100% cases, pheochromocytoma in 50% cases and multiple extra-endocrine features, many of which can be quite disabling. Only few data are available in the literature. The aim of this review is to try to give further insights into the natural history of the disease and to point out the missing evidence that would help clinicians optimize the management of such patients. MEN2B is mainly characterized by the early occurrence of MTC, which led the American Thyroid Association to recommend preventive thyroidectomy before the age of 1 year. However, as the majority of mutations are de novo, improved knowledge of the nonendocrine signs would help to lower the age of diagnosis and improve long-term outcomes. Future large-scale studies will be aimed at characterizing more in detail the main characteristics and outcomes of MEN2B.

Long-Term Survivorship in Multiple Endocrine Neoplasia Type 2B Diagnosed Before and in the New Millennium

CONTEXT

Recent long-term outcomes and survival data are lacking for patients with multiple endocrine neoplasia type 2B (MEN2B).

OBJECTIVES

To analyze long-term MEN2B outcomes and define prognostic factors.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective comparative study of 75 patients with MEN2B from two German tertiary referral centers. Patients diagnosed and treated before and after 2000 were compared for demographic, biochemical, surgical, and outcome parameters.

INTERVENTION

Surgery.

MAIN OUTCOME MEASURE

Long-term survival.

RESULTS

We identified seven familial and 68 de novo cases of MEN2B; 61 exhibited the RET M918T genotype (2 others exhibited A883F and E768D/L790T mutations). Surgery was performed at a mean age of 16.4 ± 11.2 years. The tumor stages at diagnosis for 71 patients were stage I, 15%; stage II, 6%; stage III, 35%; and stage IV, 44%. The mean follow-up was 9.6 ± 9.0 years. The outcomes were 15 (20%) cured, 9 (12%) with minimal residual disease, 19 (25%) with metastatic disease, and 10 (13%) unknown. Medullary thyroid cancer (MTC) caused 22 deaths (29%) 7.3 ± 6.2 years after diagnosis (mean age, 22.9 ± 10.7 years). The overall survival rates at 5, 10, and 20 years were 85%, 74%, and 58%, respectively. After 2000 (vs before 2000), significantly more patients had stage I and II (32% vs 11%) and more were cured (43% vs 20%), with a higher survival trend (P = 0.058). The only prognostic factor was tumor stage at diagnosis.

CONCLUSIONS

Patients with MEN2B developed MTC at an early age with wide ranging aggressiveness, but the outcome was generally better after 2000 than before 2000.

Constitutive Ret signaling leads to long-lasting expression of amphetamine-induced place conditioning via elevation of mesolimbic dopamine

Addictive drugs enhance dopamine release in the striatum, which can lead to compulsive drug-seeking after repeated exposure. Glial cell line-derived neurotrophic factor (GDNF) is an important regulator of midbrain dopamine neurons, and may play a mechanistic role in addiction-related behaviors. To elucidate the components of GDNF-signaling that contribute to addiction-related behaviors of place preference and its extinction, we utilized two genetically modified GDNF mouse models in an amphetamine-induced conditioned place preference (CPP) paradigm and evaluated how the behavioral findings correlate with dopamine signaling in the dorsal and ventral striatum. We utilized two knock-in mouse strains to delineate contributions of GDNF and Ret signaling using MEN2B mice (constitutively active GDNF receptor Ret), and GDNF hypermorphic mice (enhanced endogenous GDNF expression). The duration of amphetamine-induced CPP was greatly enhanced in MEN2B mice, but not in the GDNF hypermorphic mice. The enhanced duration of CPP was correlated with increased tyrosine hydroxylase (TH) expression and dopamine content in the ventral striatum. Together, our results suggest that downstream components of GDNF signaling, in this case Ret, may mediate persistent drug-seeking behavior through increased TH expression and dopamine levels in the mesolimbic dopamine neurons.

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.

Distribution of RET Mutations in Multiple Endocrine Neoplasia 2 in Denmark 1994-2014: A Nationwide Study

BACKGROUND

Germline mutations of the REarranged during Transfection (RET) proto-oncogene cause multiple endocrine neoplasia 2 (MEN2). It is unclear whether the distribution of RET mutations varies among populations. The first nationwide study of the distribution of RET mutations was conducted, and the results were compared to those of other populations.

METHODS

This retrospective cohort study included 1583 patients who underwent RET gene testing in one of three centers covering all of Denmark between September 1994 and December 2014. Primary testing method was Sanger sequencing, which included exons 8-11 and 13-16. Mutations were defined according to the ARUP database July 1, 2016.

RESULTS

RET mutations were identified in 163 patients from 36 apparently unrelated families. Among the 36 families 13 (36.1%) carried mutations in codon 611, four (11.1%) in codon 618, three (8.3%) in codon 620, one (2.8%) in codon 631, six (16.7%) in codon 634, one (2.8%) in codon 790, one (2.8%) in codon 804, one (2.8%) in codon 852, one (2.8%) in codon 883, and five (13.9%) in codon 918. Among the 13 families with codon 611 mutations, 12 had the p.C611Y mutation.

CONCLUSIONS

The distribution of RET mutations in Denmark appears to differ from that of other populations. Mutations in codon 611 were the most prevalent, followed by more frequently reported mutations. This might be due to a possible founder effect for the p.C611Y mutation. However, further studies are needed to find possible explanations for the skewed mutational spectrum in Denmark.

SOS1 frameshift mutations cause pure mucosal neuroma syndrome, a clinical phenotype distinct from multiple endocrine neoplasia type 2B

BACKGROUND

Mucosal neuromas, thickened corneal nerves and marfanoid body habitus are characteristic phenotypic features of multiple endocrine neoplasia type 2B (MEN2B) and often provide an early clue to the diagnosis of the syndrome. Rarely, patients present with typical physical features of MEN2B but without associated endocrinopathies (medullary thyroid carcinoma or pheochromocytoma) or a RET gene mutation; this clinical presentation is thought to represent a distinct condition termed 'pure mucosal neuroma syndrome'.

METHODS

Exome sequencing was performed in two unrelated probands with mucosal neuromas, thickened corneal nerves and marfanoid body habitus, but no MEN2B-associated endocrinopathy or RET gene mutation. Sanger sequencing was performed to confirm mutations detected by exome sequencing and to test in family members and 3 additional unrelated index patients with mucosal neuromas or thickened corneal nerves.

RESULTS

A heterozygous SOS1 gene frameshift mutation (c.3266dup or c.3248dup) was identified in each proband. Sanger sequencing showed that proband 1 inherited the c.3266dup mutation from his affected mother, while the c.3248dup mutation had arisen de novo in proband 2. Sanger sequencing also identified one further novel SOS1 mutation (c.3254dup) in one of the 3 additional index patients.

CONCLUSION

Our results demonstrate the existence of pure mucosal neuroma syndrome as a clinical entity distinct from MEN2B that can now be diagnosed by genetic testing.

Epidemiology and Clinical Presentation of Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC) is a rare neuroendocrine tumor originating from the thyroid C cells producing mainly calcitonin (CTN) used as tumor marker. MTC occurs either sporadic (75%) or in a hereditary form (multiple endocrine neoplasia type 2, MEN2), due to germline mutations in the RET proto-oncogene. The discovery of an MTC in a patient has several diagnostic implications involving a specific strategy: preoperative evaluation of the tumor marker CTN and the extent of the disease, classification of MTC as sporadic or hereditary by DNA testing, and screening for associated endocrinopathies in hereditary MTC. Elevated CTN is a highly sensitive and specific tumor marker for diagnosis and follow-up of MTC. CTN is directly related to the tumor mass. In patients with nodular thyroid disease, diagnosis of MTC could be made by CTN determination as an indicator of tumor burden in conjunction with fine-needle aspiration. Patients with confirmed sporadic or hereditary MTC should have a total thyroidectomy and depending on the preoperative CTN value and the extent of disease additional dissection of the lymph nodes in the central and lateral neck compartment. In MEN 2 patients diagnosed by screening, the time of prophylactic thyroidectomy depends on RET mutation and CTN level.

A rare case of juvenile hypertension: coexistence of type 2 multiple endocrine neoplasia -related bilateral pheochromocytoma and reninoma in a young patient with ACE gene polymorphism

BACKGROUND

Pheochromocytoma and reninoma represent two rare diseases causing hypertension. We here reported a rare case of association between type 2 multiple endocrine neoplasia related bilateral pheochromocytoma and reninoma. Moreover, polymorphism of ACE gene, which is known to be related to an increase of cardiovascular risk, has been found in the same patient.

CASE PRESENTATION

A 24 year old Caucasian man came to our attention for severe hypertension, resistant to anti-hypertensive polytherapy. At the age of twenty he had undergone total thyroidectomy with lymphadenectomy for medullary carcinoma. Genetic testing showed a RET mutation of codon 918 (exon 16) not documented in other family members. During the follow-up, a progressive increase of urinary metanephrines and catecholamines was recorded. Our evaluation confirmed the presence of severe hypertension (220/140 mmHg) and a severe increase of urinary catecholamines and metanephrines. Due to the presence of hypokalemia, other causes of hypertension were researched leading to the discovery of hyperreninemia (236 μUI/ml) with mild hyperaldosteronism, and a mild increase of the renal artery resistance at ultrasound. An abdominal MRI showed multiple adrenal masses and a right kidney nodular lesion of about 2 cm. The patient underwent bilateral adrenalectomy and right nephrectomy, and histology confirmed the presence of bilateral pheochromocytoma and right reninoma. The post-surgery laboratory evaluation showed a rapid reduction of the urinary metanephrines while plasma renin level remained low in spite of the bilateral adrenalectomy without any mineralocorticoid supplementation. To further investigate these unusual feature, we performed genetic testing for the ACE gene, which revealed the presence of ACE I/D polymorphism.

CONCLUSION

This unique report describes the association between two rare causes of hypertension in the same patient. Furthermore, the absence of requirement of mineralocorticoid supplementation in spite of bilateral adrenalectomy, represent an uncommon and interest finding.

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.

Twenty years of lesson learning: how does the RET genetic screening test impact the clinical management of medullary thyroid cancer?

OBJECTIVE

Medullary thyroid carcinoma (MTC) is a rare disease that can be inherited or sporadic; its pathogenesis is related to activating mutations in the RET gene.

DESIGN

This study describes our 20-year experience regarding RET genetic screening in MTC.

PATIENTS AND METHODS

We performed RET genetic screening in 1556 subjects, 1007 with an apparently sporadic MTC, 95 with a familial form and 454 relatives of RET-positive patients with MTC.

RESULTS

A germline RET mutation was found in 68 of 1007 (6·7%) patients with sporadic MTC, while 939 patients with MTC were negative for germline RET mutations. We then identified a total of 137 gene carriers (GC). These subjects initiated a clinical evaluation for the diagnosis of MEN 2. A total of 139 MEN 2 families have been followed: 94 FMTC, 33 MEN 2A and 12 MEN 2B. Thirty-three different germline RET mutations were identified. Codon 804 was the most frequently altered codon particularly in FMTC (32/94, 34%), while codon 634 was the most frequently altered codon in MEN 2A (31/33, 94%); MEN 2B cases were exclusively associated with an M918T mutation at exon 16.

CONCLUSIONS

Our 20-year study demonstrated that RET genetic screening is highly specific and sensitive, and it allows the reclassification as hereditary of apparently sporadic cases and the identification of GC who require an adequate follow-up. We confirmed that FMTC is the most prevalent MEN 2 syndrome and that it is strongly correlated with noncysteine RET mutations. According to these findings, a new paradigm of follow-up of hereditary MTC cases might be considered in the next future.

Primary Hyperparathyroidism in MEN2 Syndromes

One of the components of trethe classical form of MEN2 syndromes is primary hyperparathyroidism (PHP). It occurs in 20-30% of the typical MEN2A syndrome. The prevalence is more rare in gene carriers as these frequently have familial MTC only. PHP is diagnosed more frequently in association with the exon 11, codon 634 mutation of the ret gene-so there is phenotype/genotype correlation. The clinical manifestations of PHP in MEN2 are usually mild and the peak age of diagnosis after the 3rd decade. The treatment is surgical excision of the enlarged gland(s). Although there can be multigland disease in the parathyroids, it is frequently the case that both hyperplasia and adenoma may coexist, or even a single adenoma may be found during the investigation and finally during the operation. Patients with MEN2 syndromes should be screened for PHP with serum calcium measurements. The intensity of the screening should be higher in those carrying the ret mutations most frequently associated with this manifestation.

[Medullary thyroid carcinoma in a 10-month-old child with multiple endocrine neoplasia 2B]

In infants at risk of multiple endocrine neoplasia type 2B (MEN2B) the American Thyroid Association recommends genetic testing as soon as possible after birth and that thyroidectomy should be performed in MEN2B RET-mutation positive individuals as soon as possible and if possible within the first year of life. We present a ten-month-old girl with MEN2B who had prophylactic thyroidectomy. The surgical specimen showed medullary thyroid carcinoma. This case emphasizes the need for early diagnosis and prophylactic thyroidectomy in MEN2B patients.

Medullary thyroid carcinoma in children

Medullary thyroid carcinoma (MTC) originates from thyroid parafollicular C cells, and it accounts for 5% of thyroid malignancies. MTC is sporadic in approximately 80% and hereditary in 20% of cases. When hereditary it can be associated with other benign endocrine neoplasias and/or typical nonendocrine diseases, thus configuring the multiple endocrine neoplasia syndromes (type 2, MEN2/familial MTC, FMTC). Sporadic MTC is usually diagnosed in adult life. Children with clinically evident MTC are belonging to MEN2 families, particularly MEN2A and MEN2B. Children belonging to families with FMTC are usually identified by RET genetic screening shortly after birth or during childhood but they likely develop MTC later in adult life. A genotype-phenotype correlation has been observed between RET mutations and MEN2 syndromes. As for adults, the diagnosis of childhood MTC is based on serum calcitonin (Ct) and neck ultrasound with fine-needle aspiration if a thyroid nodule is present. The standard treatment is total thyroidectomy and central neck node dissection but, according to recent evidence, if the basal Ct is <30 pg/ml or following the institutional cutoff the neck node dissection can be avoided. For advanced metastatic cases, vandetanib has been demonstrated to be effective in children as well as adults.

Multiple endocrine neoplasia, the old and the new: a mini review

Multiple endocrine neoplasia syndromes have since been classified as types 1 and 2, each with specific phenotypic patterns. MEN1 is usually associated with pituitary, parathyroid and paraneoplastic neuroendocrine tumours. The hallmark of MEN2 is a very high lifetime risk of developing medullary thyroid carcinoma (MTC) more than 95% in untreated patients. Three clinical subtypesdMEN2A, MEN2B, and familial MTC (FMTC) have been defined based on the risk of pheochromocytoma, hyperparathyroidism, and the presence or absence of characteristic physical features). MEN2 occurs as a result of germline activating missense mutations of the RET (REarranged during Transfection) proto-oncogene. MEN2-associated mutations are almost always located in exons 10, 11, or 13 through 16. Strong genotype-phenotype correlations exist with respect to clinical subtype, age at onset, and aggressiveness of MTC in MEN2. These are used to determine the age at which prophylactic thyroidectomy should occur and whether screening for pheochromocytoma or hyperparathyroidism is necessary. Specific RET mutations can also impact management in patients presenting with apparently sporadic MTC. Therefore, genetic testing should be performed before surgical intervention in all patients diagnosed with MTC. Recently, Pellegata et al. have reported that germline mutations in CDKN1B can predispose to the development of multiple endocrine tumours in both rats and humans and this new MEN syndrome is named MENX and MEN4, respectively. CDKN1B. A recent report showed that in sporadic MTC, CDKN1B V109G polymorphism correlates with a more favorable disease progression than the wild-type allele and might be considered a new promising prognostic marker. New insights on MEN syndrome pathogenesis and related inherited endocrine disorders are of particular interest for an adequate surgical and therapeutic approach.

[Prophylactic thyroidectomy in medullary thyroid cancer]

Medullary thyroid cancer (MTC) is genetically determined in 30% to 35% of cases, notably through multiple mutations in the RET protooncogene located on chromosome 10, for which a genotype-phenotype relationship determines age of onset. There are three phenotypes: MEN 2 A and B, and isolated familial MTC. The type of mutation determines 3 levels of aggressiveness. Current guidelines recommend thyroidectomy during the first months of life for patients with very-high-risk (level 3) mutations and before 5 years of age for high-risk (level 2) mutations. There are no precise recommendations for lower-risk mutations, for which the surgical decision also depends on the calcitonin level and family history. We describe 18 patients who underwent prophylactic surgery. Regardless of the mutation, all patients with a normal preoperative calcitonin level were cured. However, surgery was performed later than recommended, for various reasons, including late genetic diagnosis and parents' opposition.

Multiple endocrine neoplasias type 2B and RET proto-oncogene

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

Positive selection for new disease mutations in the human germline: evidence from the heritable cancer syndrome multiple endocrine neoplasia type 2B

Multiple endocrine neoplasia type 2B (MEN2B) is a highly aggressive thyroid cancer syndrome. Since almost all sporadic cases are caused by the same nucleotide substitution in the RET proto-oncogene, the calculated disease incidence is 100-200 times greater than would be expected based on the genome average mutation frequency. In order to determine whether this increased incidence is due to an elevated mutation rate at this position (true mutation hot spot) or a selective advantage conferred on mutated spermatogonial stem cells, we studied the spatial distribution of the mutation in 14 human testes. In donors aged 36-68, mutations were clustered with small regions of each testis having mutation frequencies several orders of magnitude greater than the rest of the testis. In donors aged 19-23 mutations were almost non-existent, demonstrating that clusters in middle-aged donors grew during adulthood. Computational analysis showed that germline selection is the only plausible explanation. Testes of men aged 75-80 were heterogeneous with some like middle-aged and others like younger testes. Incorporating data on age-dependent death of spermatogonial stem cells explains the results from all age groups. Germline selection also explains MEN2B's male mutation bias and paternal age effect. Our discovery focuses attention on MEN2B as a model for understanding the genetic and biochemical basis of germline selection. Since RET function in mouse spermatogonial stem cells has been extensively studied, we are able to suggest that the MEN2B mutation provides a selective advantage by altering the PI3K/AKT and SFK signaling pathways. Mutations that are preferred in the germline but reduce the fitness of offspring increase the population's mutational load. Our approach is useful for studying other disease mutations with similar characteristics and could uncover additional germline selection pathways or identify true mutation hot spots.

Multiple endocrine neoplasia type 2B with a RET proto-oncogene A883F mutation displays a more indolent form of medullary thyroid carcinoma compared with a RET M918T mutation

BACKGROUND

Most cases of multiple endocrine neoplasia type 2B (MEN-2B) are attributable to a germline methionine to threonine mutation at codon 918 (M918T) of the RET proto-oncogene; very few cases of a germline alanine to phenylalanine mutation at codon 883 (A883F) are reported without a clear description of the clinical course. Nevertheless, RET-A883F is currently considered to be among the highest risk mutations, and prophylactic thyroidectomy is recommended as early as 6 months of life. Further characterization of the clinical behavior of RET-A883F mutation is warranted. We present the clinical data for a family with MEN-2B associated with RET-A883F mutation.

SUMMARY

The proband, a 39-year-old woman, had multifocal medullary thyroid carcinoma (MTC) with cervical lymphadenopathy, but no evidence of distant metastases. She was disease free after surgical resection. She also had bilateral pheochromocytomas and mucosal neuromas leading to the clinical diagnosis of MEN-2B. Genetic testing showed that the woman and her three children (3-5 years old) had the RET-A883F mutation. The children had near-normal calcitonin levels, and none had sonographic evidence of suspicious thyroid nodules or cervical lymphadenopathy.

CONCLUSION

A family with MEN-2B due to RET-A883F mutation displayed a less aggressive form of MTC than what is usually seen in patients with RET-M918T mutation. RET-A883F mutation could be a lower-risk mutation than previously thought and the current recommendation of prophylactic thyroidectomy in the first year of life may not be warranted. Further reports will help clarify the natural history of MTC caused by this mutation.

Single oligoarray-based detection of specific M918T mutation in RET oncogene in multiple endocrine neoplasia type 2B

The most important mutation associated with Multiple Endocrine Neoplasia type 2B (MEN 2B) is the change of thymine to cytosine in codon 918 of exon 16 in the RET oncogene (ATG → ACG). The aim of this work was to develop a single oligoarray by using tandem hybridization to detect the T918C/RET mutation for MEN 2B patients. Two genetically non-related families were studied; each family had a member affected by MEN2B. Both patients presented the T918C/RET mutation in a heterozygous fashion. None of the relatives was positive for this mutation; thus, these cases arose de novo. The proper mutation was confirmed by with different tools, PCR-Fok I endonuclease, direct sequencing, and also using our oligoarray. In this case, it is suitable to use a DNA target smaller than 150 bases with single- or double-stranded DNA and short probes of 7-mer. It was also possible to detect the mutation by employing different sources of DNA, fresh or paraffin-embedded tissues. Therefore, the present oligoarray can identify the most common M918T mutation of RET oncogene from a variety of DNA sources with good specificity and be a good alternative in the molecular diagnosis for MEN 2B cases.

Late diagnosis of type 2B multiple endocrine neoplasia (MEN 2B) in a 23 year-old patient

We present a case of MEN 2B diagnosed in a 23 year-old patient on the basis of bilateral pheochromocytoma and medullary thyroid carcinoma. This young male patient also had multiple paragangliomas located along the spine, marfanoid features of body habitus and numerous mucosal neuromas of the oral cavity and intestinal ganglioneuromatosis. The patient was hospitalised several times between the ages of 11 and 14 due to heart rhythm disorders (tachycardia, multiple supraventricular beats) and pain in the precardiac area. Elevated blood pressure was not observed at that time. In 2010, the patient was admitted to hospital due to abdominal pain, nausea, vomiting and hypertension; bilateral adrenal tumours were then detected. The patient was referred to the Department of Endocrinology in Szczecin, with suspected pheochromocytoma in order to continue the diagnostic process. This resulted in the diagnosis of bilateral pheochromocytoma and medullary thyroid carcinoma. On the basis of the whole clinical picture, the diagnosis of MEN 2B was established and subsequently confirmed with genetic test results. Following the removal of adrenal tumours and thyroidectomy, the patient was referred to the Cancer Centre and Institute of Oncology in Gliwice for further treatment (X-ray therapy and further surgery due to recurrence of medullary carcinoma). This article presents a case of late MEN 2B diagnosis despite the presence of clinical symptoms suggestive of Multiple Endocrine Neoplasia observed from early childhood.

Multiple endocrine neoplasia type 2 syndromes (MEN 2): results from the ItaMEN network analysis on the prevalence of different genotypes and phenotypes

OBJECTIVE

Multiple endocrine neoplasia type 2 (MEN 2) is a genetic disease characterized by medullary thyroid carcinoma (MTC) associated (MEN 2A and 2B) or not familial MTC (FMTC) with other endocrine neoplasia due to germline RET gene mutations. The prevalence of these rare genetic diseases and their corresponding RET mutations are unknown due to the small size of the study population.

METHODS

We collected data on germline RET mutations of 250 families with hereditary MTC followed in 20 different Italian centres.

RESULTS AND CONCLUSIONS

The most frequent RET amino acid substitution was Val804Met (19.6%) followed by Cys634Arg (13.6%). A total of 40 different germline RET mutations were present. Six families (2.4%) were negative for germline RET mutations. The comparison of the prevalence of RET germline mutations in the present study with those published by other European studies showed a higher prevalence of Val804Met and Ser891Ala mutations and a lower prevalence of Leu790Phe and Tyr791Phe (P<0.0001). A statistically significant higher prevalence of mutations affecting non-cysteine codons was also found (P<0.0001). Furthermore, the phenotype data collection showed an unexpected higher prevalence of FMTC (57.6%) with respect to other MEN 2 syndromes (34% MEN 2A and 6.8% of MEN 2B). In conclusion, we observed a statistically significant different pattern of RET mutations in Italian MEN 2 families with respect to other European studies and a higher prevalence of FMTC phenotype. The different ethnic origins of the patients and the particular attention given to analysing apparently sporadic MTC for RET germline mutations may explain these findings.

Drosophila as a novel therapeutic discovery tool for thyroid cancer

BACKGROUND

Multiple endocrine neoplasia type II (MEN2) is a rare but aggressive cancer for which no effective treatment currently exists. A Drosophila model was developed to identify novel genetic modifier loci of oncogenic RET, as well as to provide a whole animal system to rapidly identify compounds that suppressed RET-dependent MEN2. ZD6474 (Vandetanib), currently in phase III trials, suppressed tumorigenesis in MEN2 model flies, demonstrating for the first time the effectiveness of a Drosophila-based whole animal model for identifying therapeutically useful compounds.

SUMMARY

Clinical data suggest that drug mono-therapy for MEN2 and other cancers typically yield only moderate benefits as patients develop drug resistance and suffer from drug-induced pathway feedback. Combinations of drugs that target different nodes of the oncogenic pathway are an effective way to prevent resistance as well as feedback. Identifying the optimal drug-dose combinations for therapy poses a significant challenge in existing mouse models. Fly models offer a means to quickly and effectively identify drug combinations that are well tolerated and potently suppress the MEN2 phenotype. This approach may also identify differences in therapeutic responses between the two subtypes of MEN2--MEN2A and MEN2B--providing additional therapeutic insights.

CONCLUSIONS

Fly models have proven useful for identifying known drugs as well as novel compounds that, as single agents or in combinations, effectively suppress the MEN2 syndrome. These findings validate the use of fly models for both drug discovery as well as identification of useful drug combinations. In the future, rapid pairing of new genomic information with increasingly complex fly models will aid us in efforts to further tailor drug treatments toward personalized medicine.

Molecular genetics and phenomics of RET mutations: Impact on prognosis of MTC

Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant hereditary cancer syndrome caused by missense gain-of-function mutations of the RET proto-oncogene. Three distinct clinical subtypes of MEN 2 have been characterized: MEN 2A, MEN 2B, and familial medullary thyroid carcinoma (FMTC). The specific RET mutation may suggest a predilection toward a particular phenotype and clinical course, with strong genotype-phenotype correlations. Recommendations on the timing of prophylactic thyroidectomy and extent of surgery are based on classification of RET mutations into risk levels according to genotype-phenotype correlations. The excellent prognosis for MTC diagnosed at its earliest stage underscores the importance of prospective screening (calcitonin screening) for sporadic MTC and early diagnosis by RET-mutation analysis for hereditary MTC. MEN 2 provides a unique model for early prevention and cure of cancer and for the roles of stratified mutation-based diagnosis and therapy of carriers.

Genetics of the hamartomatous polyposis syndromes: a molecular review

BACKGROUND AND AIMS

Hamartomatous polyposis syndromes are a heterogeneous group of disorders that are inherited in an autosomal dominant fashion. These syndromes only represent a small number of the inherited gastrointestinal cancer predisposition syndromes. However, many of these syndromes carry a substantial risk for developing colorectal cancer, as well as extra-colonic malignancy.

MATERIALS AND METHODS

We searched for articles on inherited hamartomatous polyposis syndromes, including familial juvenile polyposis syndrome, Peutz-Jeghers syndrome, PTEN hamartoma tumor syndrome, multiple endocrine neoplasia syndrome 2B, hereditary mixed polyposis syndrome, Cronkhite-Canada syndrome, basal cell nevus syndrome, and neurofibromatosis 1, in PubMed, Embase, and Elsevier ScienceDirect. In this review, we briefly discuss the diagnosis and clinical features of these disorders and the molecular alterations responsible for these syndromes.

RESULTS AND CONCLUSION

Given the clinical similarities of these hamartomatous syndromes and the autosomal dominant pattern of inheritance, it is sometimes difficult to differentiate hamartomatous polyps, especially with atypical presentation. The molecular analysis and diagnosis make it possible to identify the subtype of these syndromes. In addition, these tests raise an intriguing possibility that surveillance and early medical intervention will allow for the identification of at-risk patients and the reduction of morbidity and mortality.

Medullary thyroid carcinoma identified within the first year of life in children with hereditary multiple endocrine neoplasia type 2A (codon 634) and 2B

CONTEXT

Early prophylactic thyroidectomy in patients with multiple endocrine neoplasia (MEN) type 2 offers the best chance for a normal life expectancy.

OBJECTIVE

To analyze the results of thyroidectomy performed during the first year of life in six patients with MEN 2A (codon 634) or MEN 2B (codon 918) syndrome.

DESIGN AND SETTING

A university hospital-based prospective study from 2001 to 2008.

SUBJECTS AND METHODS

Six family members affected either by MEN 2A (n=3) or MEN 2B (n=3) syndrome were identified through neonatal genetic screening.

RESULTS

Total thyroidectomy was performed at a median age of 0.8 year in the six patients, with central lymph node dissection in five. Bilateral millimetric medullary thyroid carcinoma (MTC) was found in all patients, with a unilateral lymph node micrometastasis in two of the three MEN 2B patients. Before thyroidectomy, MEN 2B patients had much higher basal serum calcitonin levels than those with MEN 2A and controls. After thyroidectomy, with a median follow-up of 3.3 years, the six patients had no evidence of persistent MTC.

CONCLUSION

Bilateral millimetric MTC may be present during the first year of life in these patients, with lymph node metastases also occurring in MEN 2B patients. These results support a total thyroidectomy at the age of about one year in MEN 2A (codon 634) children with an abnormal serum calcitonin level, and a total thyroidectomy with central neck dissection within the first weeks of life in MEN 2B patients.

Transcriptome analysis in mouse tumors induced by Ret-MEN2/FMTC mutations reveals subtype-specific role in survival and interference with immune surveillance

Activating mutations in the Ret proto-oncogene are responsible for occurrence of multiple endocrine neoplasia (MEN) type 2A and 2B, and familial medullary thyroid carcinoma (FMTC). A striking genotype-phenotype correlation between the mutated RET codon and clinical manifestation implies that tumorigenesis is conditioned by the type of mutation. We investigated gene expression profiles between and within distinct MEN2 subtypes through whole-genome microarray analysis in tumors induced by NIH-3T3 cells transformed with defined RET-MEN2A (C609Y, C634R), MEN2B, (A883F, M918T), and FMTC (Y791F) mutations. Expression profiling identified a statistically significant modification of 1494 genes, 628 down- and 866 upregulated in MEN2B compared with MEN2A/FMTC tumors. By contrast, no obvious alterations were observed among individual MEN2B and MEN2A type mutations, or between MEN2A and FMTC. Functional clustering of differential genes revealed RET-MEN2B specific upregulation of genes associated with novel growth and survival pathways. Intriguingly, RET-MEN2A/FMTC-specific tumors were characterized by a considerable number of genes involved in the host antitumor immune response via stimulation of natural killer/T-cell proliferation, migration, and cytotoxicity, which were completely absent in RET-MEN2B related cancers. QPCR on tumors versus cultured NIH-RET cell lines demonstrated that they are largely attributed to the host innate immune system, whereas expression of CX3CL1 involved in leukocyte recruitment is exclusively RET-MEN2A/FMTC tumor cell dependent. In correlation, massive inflammatory infiltrates were apparent only in tumors carrying MEN type 2A/FMTC mutations, suggesting that RET-MEN2B receptors specifically counteract immune infiltration by preventing chemokine expression, which may contribute to the different clinical outcome of both subtypes.

Genotype-phenotype relationship in multiple endocrine neoplasia type 2. Implications for clinical management

Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant tumour syndrome caused by germline activating mutations of the RET proto-oncogene. It has a strong penetrance of medullary thyroid carcinoma (MTC) and can be associated with bilateral pheochromocytoma and primary hyperparathyroidism (MEN2A) within a single patient or family. Based on the phenotype three distinct clinical forms have been described: (1) classical MEN2A, (2) MEN2B, an association of MTC, pheochromocytoma and mucosal neuroma and (3) familial MTC (FMTC), which is associated with a very low incidence of other endocrinopathies. Each variant of MEN2 results from a different RET gene mutation, with a good genotype-phenotype correlation with regard to aggressiveness of MTC, time of onset of MTC and the presence or absence of other endocrine tumours. Recommendations on the timing of prophylactic thyroidectomy and extent of surgery are based on a classification of RET mutations into three risk levels using the genotype-phenotype correlations. MEN2 provides a unique model for early prevention and cure of cancer and for stratified roles of mutation-based diagnosis of carriers.

The genetic basis of hereditary medullary thyroid cancer: clinical implications for the surgeon, with a particular emphasis on the role of prophylactic thyroidectomy

Medullary thyroid cancer (MTC) may occur either sporadically or on a hereditary basis. Hereditary MTC may be observed with either multiple endocrine neoplasia syndromes (MEN 2A and MEN 2B) or as familial MTC (FMTC). Despite the rarity of these syndromes, early diagnosis is especially important, since MTC is a lethal disease if not promptly and appropriately treated. Recently, the development of genetic testing and direct DNA analysis allows the identification of asymptomatic patients. Surgical prophylaxis should be considered in these cases, ideally to prevent the development of MTC. During the recent decade, the concept of 'codon-directed' timing of prophylactic surgery emerged as a reasonable strategy in the management of these patients. Currently, genetic analysis offers the possibility to define genotype-phenotype correlations and to adjust the time of prophylactic surgery. Hereditary MTC is a model of genetically determined cancer in which both diagnostic and therapeutic strategies rely on the identification of specific mutations.

Orolabial signs are important clues for diagnosis of the rare endocrine syndrome MEN 2B. Presentation of two unrelated cases

Multiple endocrine neoplasia syndromes (MEN) are genetic disorders with glandular hyperplasia and consecutive malignant neoplasia. MEN type 2B is the least common form of these tumor syndromes. It presents with typical dysmorphic features, mucosal neuromas, ganglioneuromatosis, medullary thyroid carcinoma (MTC) and phaeochromocytoma. The prognosis depends on the presence of MTC. We have surprisingly found two unrelated patients with this syndrome at our department within two weeks. In the medical history of a 17-year-old boy, Crohn's disease had been considered because of abdominal pain and distention. He had marfanoid appearance and previously undergone minor surgeries for a large tongue with neuromas and hypertrophic gums. Two weeks later, a 10-year-old girl presented with a hard palpable mass on her neck. She had thickened lips, neuromas on the tongue and a solitary thyroid nodule. Genetic analysis was carried out in both patients and a heterozygous M918T mutation of the RET proto-oncogene was found. Laboratory tests and imaging studies were consistent with MTC. Phaeochromocytoma was not present. Both patients underwent total thyroidectomy and lymph node dissection. Histological examination confirmed the diagnosis of MTC. In conclusion, the initial diagnosis of MEN 2B should be suspected on the presence of typical facial/oral signs and gastrointestinal symptoms. Hormonal tests and imaging techniques of the thyroid and the adrenals can confirm the clinical diagnosis of MEN 2B and genetic analysis can prove its germline origin.

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.

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

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

RET(MEN 2B) is active in the endoplasmic reticulum before reaching the cell surface

MEN 2B (multiple endocrine neoplasia type 2B) is an autosomal dominant cancer syndrome caused by an oncogenic form of the receptor tyrosine kinase REarranged during transfection (RET). The MEN 2B syndrome is associated with an abnormal autophosphorylation of the mutated receptor even without ligand-stimulation. Here, we characterize the activation of a RET(MEN 2B) variant carrying the point mutation Met918Thr, and show that the 150 kDa precursor of RET(MEN 2B) becomes phosphorylated already during synthesis in the endoplasmic reticulum (ER). At least three different tyrosine residues (Tyr905, Tyr1062, Tyr1096) of the RET(MEN 2B) precursor are phosphorylated before the oncogenic receptor reaches the cell surface. We also demonstrate that the precursor of RET(MEN 2B) interacts with both growth factor receptor-bound protein and Src homology 2 domain-containing already in the ER, and that this interaction is dependent on the kinase activity of RET. With the aid of two RET mutants (RET(MEN 2B/S32L) and RET(MEN 2B/F393L)), which accumulate in the ER, we show that the oncogenic precursor of the receptor has the capacity to activate AKT, extracellular signal-regulated kinase and signal transducer and activator of transcription 3 from the ER. Taken together, our data demonstrate that the oncogenic precursor of RET(MEN 2B) is phosphorylated, interacts with adapter proteins and induces downstream signalling from the ER.