Multiple endocrine neoplasia type 2: A review.

Multiple endocrine neoplasias are rare hereditary syndromes some of them with malignant potential. Multiple endocrine neoplasia type 2 (MEN 2) is an autosomal dominant hereditary cancer syndrome due to germline variants in the REarranged during Transfection (RET) proto-oncogene. There are two distinct clinical entities: MEN 2A and MEN 2B. MEN 2A is associated with medullary thyroid carcinoma (MTC), phaeochromocytoma, primary hyperparathyroidism, cutaneous lichen amyloidosis and Hirschprung's disease and MEN 2B with MTC, phaeochromocytoma, ganglioneuromatosis of the aerodigestive tract, musculoskeletal and ophthalmologic abnormalities. Germline RET variants causing MEN 2 result in gain-of-function; since the discovery of the genetic variants a thorough search for genotype-phenotype associations began in order to understand the high variability both between families and within family members. These studies have successfully led to improved risk classification of prognosis in relation to the genotype, thus improving the management of the patients by thorough genetic counseling. The present review summarizes the recent developments in the knowledge of these hereditary syndromes as well as the impact on clinical management, including genetic counseling, of both individual patients and families. It furthermore points to future directions of research for better clarification of timing of treatments of the various manifestations of the syndromes in order to improve survival and morbidity in these patients.

Fifty Years After the First Description, MEN 2B Syndrome Diagnosis Is Still Late: Descriptions of Two Recent Cases.

BACKGROUND: Multiple endocrine neoplasia type 2B (MEN 2B) is a very rare syndrome characterized by a very peculiar phenotype with mucosal neuromas, marfanoid habitus, and bumpy lips associated with medullary thyroid cancer (MTC) and pheochromocytoma (PHEO). Although the syndrome was first described 50 years ago, it is still diagnosed too late, when the MTC is metastatic and frequently when the PHEO has already developed. CASE PRESENTATIONS: We report on two cases of MEN 2B that were diagnosed too late, preventing a cure. The cases involve two females who were 25 and 12 years old. Both were previously treated for congenital skeletal abnormalities; however, despite their bumpy lips and mucosal neuromas, MEN 2B syndrome was not recognized. When they arrived at our center for both the presence of thyroid nodules and elevated serum calcitonin values, the MTC was already metastatic, and the older patient had already developed a bilateral PHEO. After 3 years and 1 year of follow-up, the two patients are still alive but with persistent structural and biochemical disease. DISCUSSION: These two cases show that knowledge of this syndrome is still insufficient and that the lack of knowledge impairs the ability to obtain an early diagnosis and cure. Because most patients with MEN 2B have no familial history, the only way to ensure a timely diagnosis is to recognize the MEN 2B phenotype on a clinical basis.

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.

Pheochromocytomas in Multiple Endocrine Neoplasia Type 2.

Pheochromocytoma (PC) is a neuroendocrine tumor that originates from chromaffin cells of the adrenal medulla. The production of catecholamines, including epinephrine, norepinephrine and dopamine, may lead to haemodynamic instability. Over 30% of PCs are associated with germline mutations, including re-arranged in transfection (RET) mutations seen in multiple endocrine neoplasia type 2 (MEN2) syndromes. Around 40% of individuals with MEN2 develop PC, though it is rarely the presenting feature. Compared to sporadic PC, MEN2-associated PC is more likely to be epinephine secreting and demonstrate bilateral adrenal involvement, and is less likely to be malignant. The diagnosis of PC requires clinical suspicion and biochemical testing, followed by imaging studies. Novel nuclear medicine modalities, including FDG positron emission tomography (PET) and 68Ga DOTATATE PET have added to the conventional techniques of 123I-metaiodobenzylguanindine (MIBG) scintigraphy, computer tomography and magnetic resonance imaging. Treatment of PC is surgical and requires peri-operative alpha and, frequently, beta blockade. Novel surgical techniques, such as adrenal sparing surgery and a laparoscopic approach, have decreased peri-operative morbidity. Surveillance for PC is life long, due to the risk of metastatic disease.

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.

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.

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.

Sporadic and familial medullary thyroid carcinoma: state of the art.

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

RET oncogene in MEN2, MEN2B, MTC and other forms of thyroid cancer.

Hereditary medullary thyroid carcinoma (MTC) is caused by specific autosomal dominant gain-of-function mutations in the RET proto-oncogene. Genotype-phenotype correlations exist that help predict the presence of other associated endocrine neoplasms as well as the timing of thyroid cancer development. MTC represents a promising model for targeted cancer therapy, as the oncogenic event responsible for initiating malignancy has been well characterized. The RET proto-oncogene has become the target for molecularly designed drug therapy. Tyrosine kinase inhibitors targeting activated RET are currently in clinical trials for the treatment of patients with MTC. This review will provide a brief overview of MTC and the associated RET oncogenic mutations, and will summarize the therapies designed to strategically interfere with the pathologic activation of the RET oncogene.

Phenotypic multiple endocrine neoplasia type 2B, without endocrinopathy or RET gene mutation: implications for management.

The multiple endocrine neoplasia (MEN) type 2B is an autosomal dominant condition characterized by aggressive medullary C-cell tumors, pheochromocytoma, and a discrete physical appearance (marfanoid habitus, prominent corneal nerve fibers, thick lips, and mucosal and intestinal neuromas). A specific point mutation in the RET proto-oncogene is present in 95% cases. Occasionally cases present with the characteristic physical appearance of MEN 2B but no identifiable germline mutation or endocrinopathy, and it has been suggested that these patients may represent a discrete subgroup termed pure mucosal neuroma syndrome (MNS). We present a patient with MNS, who had a thyroidectomy at age 14.5 years with normal thyroid histology. Direct sequencing of all 20 exons of the RET gene showed no mutation. This case supports the suggestion that pure MNS can exist in the absence of an identifiable RET gene mutation. We suggest that prophylactic thyroidectomy is unnecessary in these patients although they should still be screened for endocrinopathy on a regular basis.

Multiple endocrine neoplasia type 2B and Hirschsprung's disease.

Multiple endocrine neoplasia type 2B and Hirschsprung's disease are genetic disorders characterized by gross and/or microscopic pathology of the enteric nervous system and associated dysmotility. A specific missense mutation in the RET proto-oncogene is the etiology of multiple endocrine neoplasia type B, in contrast to very complex multigenetic defects that underlie Hirschsprung's disease, which include overt mutations and more subtle changes in the RET locus. In this review, the molecular genetics of the 2 conditions are discussed, and the clinical implications of existing data and future studies are summarized.

Multiple endocrine neoplasia syndrome: genetic basis for clinical management.

PURPOSE OF REVIEW: Multiple endocrine neoplasia (MEN) types 1 and 2 are rare hereditary cancer syndromes expressing a variety of mainly endocrine neoplasias. Improved understanding of the molecular and clinical genetics associated with these lesions will likely enhance the diagnosis and treatment of patients with these diseases. RECENT FINDINGS: The MEN1 gene causing MEN1 is a tumor suppressor gene and seems to act as a regulator of the transcriptional machinery. Novel genetic and diagnostic modalities tend to identify neoplastic lesions at an earlier stage, potentially improving outcome and quality of life. Improved understanding of genotype-phenotype correlations in MEN2, caused by a mutation in the RET oncogene, may enable a more individualized treatment for these patients. SUMMARY: Recent advances in molecular pathology, diagnosis, and management of patients with MEN1 and MEN2 are reviewed.

[Multiple endocrine neoplasia type 2]. / Neoplasia endócrina múltipla tipo 2.

The term multiple endocrine neoplasia (MEN) was introduced by Steiner et al. in 1968 to describe disorders that include a combination of endocrine tumors. The Wermer syndrome was designed as MEN 1 and the Sipple syndrome as MEN 2. Sizemore et al. (1974) completed that the MEN 2 category included 2 subgroups: patients with medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid disease and a normal appearance (MEN 2A) and other without parathyroid disease but with mucosal neuromas and mesodermal abnormalities (MEN 2B). MTC is usually the first tumor diagnosed. The diagnosis of MTC has several implications: disease extent should be evaluated, pheochromocytoma and hyperparathyroidism should be screened and whether the MTC is sporadic or hereditary should be determined by a direct analysis of the RET proto-oncogene. Here, the pathological characteristics, genetic abnormalities, and clinical features of MEN 2 are discussed. The diagnostic and therapeutic approaches used to patients with clinical disease and carriers identified through familiar screening are also described. Progresses related especially to genetic screening and earlier intervention have permitted an improvement in the long-term outcome. However, treatment for disseminated disease is still ineffective.

[Management of multiple endocrine neoplasia syndrome type 2 families in association with rare germline mutations of the RET proto-oncogene]. / Management von Familien mit einem multiplen endokrinen Neoplasie-Syndrom Typ 2 in Assoziation mit seltenen Keimbahnmutationen des RET-Protoonkogens.

INTRODUCTION: Heredity of MEN2 syndromes is caused by a heterozygous germline mutation in the RET proto-oncogene. This study describes families with rare noncysteine codon 790/791 mutations and discusses the genotype-phenotype correlation plus the therapeutic options. PATIENTS AND METHODS: Forty-five patients with a putative sporadic MTC were screened for RET germline mutations by direct DNA sequencing. Family members of identified index cases underwent genetic analysis. Gene carriers were examined clinically and biochemicaly and underwent prophylactic thyroidectomy. RESULTS: Five index patients were identified. In the kindreds three L790F and one Y791F carriers were detected. The thyroid gland histology of L790F carriers revealed MTC in 2 patients and C-cell hyperplasia in 2 additional patients. The Y791F carrier had a normal histology. CONCLUSIONS: Codon 790/791 mutations had diverse penetrance: prophylactic thyreoidectomy in children is a justifiable approach for codon 790 mutation carriers, but should depend on the clinical course of codon 791 carriers.

[Results of treating medullary thyroid carcinoma: the differences between sporadic and inherited forms]. / Wyniki leczenia raka rdzeniastego tarczycy: róznice pomiedzy postaciami sporadyczna i dziedziczna.

Medullary thyroid carcinoma (MTC) can be divided into two subgroups: sporadic or inherited. Hereditary form of MTC is often believed to be form with better prognosis than sporadic one. In this study the differences in MTC prognosis in Polish population of patients was analyzed. The group of 169 patients with MTC was examined. Hereditary cancer was stated in 48 (28%) patients. The median age of disease onset was 41 years (from 7 to 71 years). Genetic examination of RET protooncogene was performed in all patients. The calcitonin and CEA serum level analysis and radiological and radioisotopic examinations were used for monitoring of the disease course. Nineteen cases of MEN 2A syndrome, 11 cases of MEN 2B one and 18 cases of non classified familial MTC were recognized among patients with inherited MTC. Significantly lower age of disease onset in inherited MTC than in sporadic one was observed (27 years vs. 43.7 years, p < 0.001). Local or nodal recurrence was observed in 22 (13%) patients, distant metastases were stated in 21 (12%) patients. Basal or stimulated serum calcitonin level was increased in 85 (50%) patients. No significant differences between sporadic and inherited disease were observed. Eight patients died during observation, including 3 patients with sporadic MTC and 5 patients with inherited MTC. The updated 10-year survival rate was 97% in patients with sporadic MTC; in hereditary MTC it was about 20% worse. The complications related to the presence of adrenal tumors were the main reason for death in MEN2 and no significant differences in the course of MTC itself were observed.

Intestinal ganglioneuromatosis and multiple endocrine neoplasia type 2B: implications for treatment.

Three infants, who presented with intestinal obstruction due to diffuse transmural intestinal ganglioneuromatosis, are described. Mutation analysis of exon 16 of the RET proto-oncogene revealed germline M918T and thus, a molecular diagnosis of multiple endocrine neoplasia type 2B (MEN 2B). Two infants developed medullary carcinoma of the thyroid. The third had a prophylactic thyroidectomy despite no obvious thyroid masses and normal calcitonin concentrations, but microscopic multifocal medullary carcinoma was found on histological examination. Early recognition of intestinal ganglioneuromatosis with germline RET M918T mutation in pseudo-Hirschsprung's disease is an indication for prophylactic thyroidectomy.

Clinical and molecular aspects of multiple endocrine neoplasia.

The discovery that RET proto-oncogene mutations are responsible for MEN2 and FMTC was a landmark from the perspective of many, including the geneticist involved in basic science, the molecular diagnostician, the clinician, and MEN2/FMTC families. The discovery has provided basic information concerning the role of proto-oncogenes and proto-oncogene activation. The identification of MEN2/FMTC-associated mutations has also allowed for the availability of direct mutation analysis in the routine clinical laboratory. The discovery has resulted in definitive risk assessment for members of FMTC/MEN2 kindreds and improved management of RET mutation carriers. The discovery also links two realms of genetics that are often separated: cancer genetics and "classic" mendelian disorders. Finally, information concerning the molecular basis of Hirschsprung disease indicates that our understanding of the phenotypic consequences of RET mutations is considerable but not yet complete.