Genotype-phenotype correlation in multiple endocrine neoplasia type 2

Multiple Endocrine Neoplasia Type 1, Type 2A, and Type 2B

Multiple endocrine neoplasia type 1 is a rare genetic neuroendocrine syndrome caused by over 1500 different germline mutations. It can cause 20 different endocrine tumors affecting primarily the parathyroid glands, gastroenteropancreatic tract, and the anterior pituitary gland. Multiple endocrine neoplasia type 2A (MEN2A) and Multiple endocrine neoplasia type 2B (MEN2B) are autosomal dominant genetic syndromes because of a germline variant in the 'rearranged during transfection' (RET) proto-oncogene. There are common RET mutations causing receptor hyperactivation and induction of downstream signals that cause oncogenesis. Common conditions with MEN2A are medullary thyroid cancer (MTC), pheochromocytoma, and primary hyperparathyroidism. Common conditions with MEN2B include MTC, pheochromocytomas, and benign ganglioneuromas.

Genetics of Cardiac Tumours: A Narrative Review

Cardiac tumours can occur in association with genetic syndromes. Rhabdomyomas have been reported in association with tuberous sclerosis, myxomas with Carney's complex, cardiac fibromas with Gorlin syndrome, and paragangliomas with multiple endocrine neoplasm syndrome. The presentation and prognosis of cardiac tumours associated with genetic syndromes differ compared with sporadic cases. Knowledge about the associated syndromes' genetic features and extracardiac manifestations is essential for the diagnosis, prognosis, and management of cardiac neoplasms. Moreover, identifying genetic mutations in benign and malignant cardiac tumours is needed to personalise management and improve treatment outcomes. Thus, this review discusses the genetic abnormalities associated with cardiac tumours, the current genetic screening recommendations, and the effect of those genetic mutations on the outcomes.

Genetics of hereditary forms of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT), a relatively common disorder characterized by hypercalcemia with raised or inappropriately normal serum parathyroid hormone (PTH) concentrations, may occur as part of a hereditary syndromic disorder or as a non-syndromic disease. The associated syndromic disorders include multiple endocrine neoplasia types 1-5 (MEN1-5) and hyperparathyroidism with jaw tumor (HPT-JT) syndromes, and the non-syndromic forms include familial hypocalciuric hypercalcemia types 1-3 (FHH1-3), familial isolated hyperparathyroidism (FIHP), and neonatal severe hyperparathyroidism (NS-HPT). Such hereditary forms may occur in > 10% of patients with PHPT, and their recognition is important for implementation of gene-specific screening protocols and investigations for other associated tumors. Syndromic PHPT tends to be multifocal and multiglandular with most patients requiring parathyroidectomy with the aim of limiting end-organ damage associated with hypercalcemia, particularly osteoporosis, nephrolithiasis, and renal failure. Some patients with non-syndromic PHPT may have mutations of the MEN1 gene or the calcium-sensing receptor (CASR), whose loss of function mutations usually cause FHH1, a disorder associated with mild hypercalcemia and may follow a benign clinical course. Measurement of the urinary calcium-to-creatinine ratio clearance (UCCR) may help to distinguish patients with FHH from those with PHPT, as the majority of FHH patients have low urinary calcium excretion (UCCR < 0.01). Once genetic testing confirms a hereditary cause of PHPT, further genetic testing can be offered to the patients' relatives and subsequent screening can be carried out in these affected family members, which prevents inappropriate testing in normal individuals.

[Precision medicine in endocrinology exemplified by medullary thyroid cancer]

Medullary thyroid cancer (MTC) is a prime example for precision medicine in endocrinology and underlines the immediate benefits of basic, translational and healthcare research for patients with a rare disease in clinical . A mutation in the rearranged during transfection (RET) proto-oncogene that codes for a transmembrane receptor protein tyrosine kinase, leads to constitutive activation of the kinase, which is the decisive pathomechanism for the disease. The MTC occurs in a sporadic (somatic RET mutation) or hereditary form (RET germline mutation, multiple endocrine neoplasia types 2 and 3). For germline mutation carriers the timing of preventive thyroidectomy depends on the RET genotype. For advanced metastasized RET-mutant MTC, selective RET kinase inhibitors are available, which are currently considered to be game changers in the treatment. Based on the specific tumor marker calcitonin, MTC can be identified at an early stage during the differential diagnosis of thyroid nodules. The preoperative calcitonin level even enables statements on the degree of dissemination of the disease and on the probability of a cure through surgery. A new development is the consideration of desmoplasia as a histopathological biomarker for the metastatic potential of a MTC, which could possibly modify the operative approach as well as the future MTC nomenclature. Furthermore, the postoperative calcitonin level and the calcitonin doubling time are highly valid prognostic markers for tumor burden and biological aggressiveness of MTC and therefore decisive for patient follow-up. Biochemical, molecular and histological markers enable a risk-adapted surgical treatment and together with new targeted systemic treatments have contributed to a paradigm shift in the diagnostics, prognosis and treatment of MTC in recent years. Endocrine precision medicine for MTC therefore enabled a change from the previous purely symptom-oriented to a modern preventive and individualized treatment.

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.

Multiple endocrine neoplasia type 2: A reveiw

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.

Medullary thyroid cancer: molecular factors, management and treatment

Medullary thyroid cancer (MTC) is an infrequent neuroendocrine tumor, which amounts to 3–5% of all thyroid malignancies. Approximately 75–80% of MTCs are sporadic neoplasms. The rest of 20–25% are familial cases that belong to multiple endocrine neoplasia (MEN) syndromes, specifically MEN2 and MEN3. These cases of familial MTC are attributed to an activating germline mutation of a tyrosine kinase receptor gene, the rearranged during transfection (RET) proto-oncogene, located on chromosome 10q11.21. These mutations are also found in some cases of sporadic MTC. This review sets forth in summary the accepted guidelines and approaches regarding diagnosis, management, and treatment of MTC. Surgical resection is the standard care, and an early, prophylactic intervention is performed in genetic cases. Further investigation and understanding of the molecular pathways involved in the growth and advancement of MTC is required in order to provide efficient therapy in cases of progressive disease.

Long-term Clinicopathological Features of a Family with Multiple Endocrine Neoplasia Type 2A Caused by C634R RET Gene Mutation

Type 2 multiple endocrine neoplasia (MEN2A) is a variant of hereditary medullary thyroid carcinoma (MTC). MEN2A is characterized by the presence of the following: MTC, hyperparathyroidism, and pheochromocytoma (PHEO). The pathogenesis includes RET proto-oncogene mutation; the most frequently observed mutation is in exon 11 codon 634. We report pedigree of a large Indian family involving three generations including 21 members with MEN2A, in whom RET mutation status was determined. We then analyzed their clinical follow-up details, with a median duration of follow-up of 60 months (range: 9-276 months). Calcitonin (Ctn) levels were routinely checked during the follow-up. The index case was found to carry p.C634R mutation involving exon 11 of the RET gene. RET mutation was positive in 12 members in the family (12/21, i.e., 57%), was negative in 7 patients, and was not tested in 2 patients, as they were not available for the genetic test. Thirteen were clinically affected with MTC and 10 members had PHEO. At the last follow-up, the median Ctn level was 14.3 pg/mL (range: 2-12655 pg/mL). Four patients developed lymph nodal recurrence during follow-up, for which they underwent re-operations with median duration to recurrence being 48 months (range: 9-156 months). We highlight in this article that early diagnosis, adequate surgery, and appropriate genetic counseling with genetic screening are essential to improve the outcome of persons with MTC. Every case of MTC should be seen as familial or index case of hereditary MTC unless otherwise RET mutation excludes it.

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

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

Twenty-Five Years Experience on RET Genetic Screening on Hereditary MTC: An Update on The Prevalence of Germline RET Mutations

BACKGROUND

Pathogenic germline mutations affecting the RET proto-oncogene underlie the development of hereditary medullary thyroid carcinoma (MTC). The aims of this study were to evaluate the prevalence of germline RET mutations in a large series of MTC, collected over the last 25 years, and to reappraise their clinical significance.

METHODS

We performed RET genetic screening in 2031 Italian subjects: patients who presented with sporadic (n = 1264) or hereditary (n = 117) MTC, plus 650 relatives.

RESULTS

A RET germline mutation was found in 115/117 (98.3%) hereditary and in 78/1264 (6.2%) apparently sporadic cases: in total, 42 distinct germline variants were found. The V804M mutation was the most prevalent in our cohort, especially in cases that presented as sporadic, while mutations affecting cysteine residues were the most frequent in the group of clinically hereditary cases. All M918T mutations were "de novo" and exclusively associated with MEN2B. Several variants of unknown significance (VUS) were also found.

CONCLUSIONS

a) RET genetic screening is informative in both hereditary and sporadic MTC; b) the prevalence of different mutations varies with V804M being the most frequent; c) the association genotype-phenotype is confirmed; d) by RET screening, some VUS can be found but their pathogenic role must be demonstrated before screening the family.

Prophylactic thyroidectomy in multiple endocrine neoplasia type 2A in children: a single centre experience

Background To describe the complications and long-term results in patients with multiple endocrine neoplasia type 2A (MEN 2A) syndrome in whom a prophylactic thyroidectomy was performed, in relation to the recommendations of the American Thyroid Association (ATA). Methods A retrospective study of 14 patients with MEN 2A thyroidectomized between 2000 and 2017. We reviewed demographic, clinical, analytical and radiological data. Postoperative complications and long-term follow-up were analyzed. Results We treated eight boys and six girls with a median age of 5 years old (range 2-10). The predominant genetic mutation belonged to codon 634 (8/14, 57.14%). Total thyroidectomy (TT) without cervical lymphadenectomy was performed in all patients. A right upper parathyroidectomy was performed in one patient due to intraoperative suspicion of increased volume. Histological study revealed no alterations. Two patients presented transient hypocalcemia postoperatively and no patient had permanent hypocalcemia or nerve damage. Pathological anatomy confirmed medullary thyroid microcarcinoma in 5/14 patients: all carrying codon 634 mutation and three of them with preoperative basal calcitonin levels <20 pg/mL. No recurrences or metastases have been detected after a mean follow-up of 8 years. A patient with codon 634 mutation developed a unilateral pheochromocytoma at 25 years of age. No patient has presented hyperparathyroidism. Conclusions Prophylactic thyroidectomy without cervical lymphadenectomy is an effective and safe preventive treatment in patients with MEN 2A syndrome when it is performed by experienced surgeons in reference centers.

Pheochromocytomas and Paragangliomas: New Developments with Regard to Classification, Genetics, and Cell of Origin

Pheochromocytomas (PCC) and paragangliomas (PGL) are rare neuroendocrine tumors that arise in the adrenal medulla and in extra-adrenal locations, such as the head, neck, thorax, abdomen, and pelvis. Classification of these tumors into those with or without metastatic potential on the basis of gross or microscopic features is challenging. Recent insights and scoring systems have attempted to develop solutions for this, as described in the latest World Health Organization (WHO) edition on endocrine tumor pathology. PCC and PGL are amongst the tumors most frequently accompanied by germline mutations. More than 20 genes are responsible for a hereditary background in up to 40% of these tumors; somatic mutations in the same and several additional genes form the basis for another 30%. However, this does not allow for a complete understanding of the pathogenesis or targeted treatment of PCC and PGL, for which surgery is the primary treatment and for which metastasis is associated with poor outcome. This review describes recent insights into the cell of origin of these tumors, the latest developments with regard to the genetic background, and the current status of tumor classification including proposed scoring systems.

An Update on the Histology of Pheochromocytomas: How Does it Relate to Genetics?

Pheochromocytomas are rare neuroendocrine tumors of the adrenal gland, whereas any extra-adrenal tumor with similar histology is designated as paraganglioma. These tumors have a very high rate of germline mutations in a large number of genes, up to 35% to 40%, frequently predisposing for other tumors as well. Therefore, they represent a phenomenal challenge for treating physicians. This review focuses on pheochromocytomas only, with special attention to gross and microscopic clues to the diagnosis of genetic syndromes, including the role of succinate dehydrogenase subunit A and subunit B immunohistochemistry as surrogate markers for genetic analysis in the field of succinate dehydrogenase subunit gene mutations.

Molecular pathogenesis of parathyroid tumours

Parathyroid tumors represent an elusive endocrine neoplasia, which lead to primary hyperparathyroidism, pHPT, a common endocrine calcium disorder characterized by hypercalcemia and normal-high parathormone secretion. Parathyroid tumours are benign adenomas or multiple glands hyperplasia in the vast majority (>99% of cases), while malignant neoplasms are rare (less than 1%). Despite pHPT is a common disorder, our knowledge about the genetic predisposition and molecular pathophysiology is limited to the familial syndromic forms of parathyroid tumour, that, however, represent not more than the 10% of all the cases; instead, the pathophysiology of sporadic forms remains an open field, although data about epigenetic mechanisms or private genes have been supposed. Here we present an overview of more recent acquisitions about the genetic causes along with their molecular mechanisms of benign, but also, malignant parathyroid tumours either in sporadic and familial presentation.

A Novel RET D898Y Germline Mutation in a Patient with Pheochromocytoma

Pheochromocytoma and paraganglioma are tumors of neuroectoderm origin. Up to 40% of patients with these tumors have germline mutations in known susceptibility genes. We report a novel RET germline mutation (exon 15; c.2692G>T (D898Y)) in a pheochromocytoma patient, as well as in her two asymptomatic sons and older sister. A 49-year-old female came to our clinic presenting with a right adrenal gland mass detected during a healthcare examination. Her mother and two sisters had previously undergone thyroidectomy for papillary thyroid carcinomas. The levels of vanillylmandelic acid and other catecholamines were elevated in 24-hour urine, and an imaging study revealed a right adrenal mass. She underwent laparoscopic adrenalectomy and the final pathologic diagnosis was pheochromocytoma. Mutation screening detected a RET p.D898Y mutation, both in the patient and in the patient's two sons and older sister. This is the first description of a RET D898Y mutation in a pheochromocytoma patient and her family. The mutation should be categorized as a variant of unknown significance because no RET gene related disorders were detected in this family. Long term follow-up will be required to determine the clinical significance of the RET D898Y mutation.

Multiple Endocrine Neoplasia and Hyperparathyroid-Jaw Tumor Syndromes: Clinical Features, Genetics, and Surveillance Recommendations in Childhood

Children and adolescents who present with neuroendocrine tumors are at extremely high likelihood of having an underlying germline predisposition for the multiple endocrine neoplasia (MEN) syndromes, including MEN1, MEN2A and MEN2B, MEN4, and hyperparathyroid-jaw tumor (HPT-JT) syndromes. Each of these autosomal dominant syndromes results from a specific germline mutation in unique genes: MEN1 is due to pathogenic MEN1 variants (11q13), MEN2A and MEN2B are due to pathogenic RET variants (10q11.21), MEN4 is due to pathogenic CDKN1B variants (12p13.1), and the HPT-JT syndrome is due to pathogenic CDC73 variants (1q25). Although each of these genetic syndromes share the presence of neuroendocrine tumors, each syndrome has a slightly different tumor spectrum with specific surveillance recommendations based upon tumor penetrance, including the age and location for which specific tumor types most commonly present. Although the recommended surveillance strategies for each syndrome contain similar approaches, important differences do exist among them. Therefore, it is important for caregivers of children and adolescents with these syndromes to become familiar with the unique diagnostic criteria for each syndrome, and also to be aware of the specific tumor screening and prophylactic surgery recommendations for each syndrome. Clin Cancer Res; 23(13); e123-e32. ©2017 AACRSee all articles in the online-only CCR Pediatric Oncology Series.

Extent of surgery for phaeochromocytomas in the genomic era

Background

Germline mutations are present in 20–30 per cent of patients with phaeochromocytoma. For patients who develop bilateral disease, complete removal of both adrenal glands (total adrenalectomy) will result in lifelong adrenal insufficiency with an increased risk of death from adrenal crisis. Unilateral/bilateral adrenal-sparing surgery (subtotal adrenalectomy) offers preservation of cortical function and independence from steroids, but leaves the adrenal medulla in situ and thus at risk of developing new and possibly malignant disease. Here, present knowledge about how tumour genotype relates to clinical behaviour is reviewed, and application of this knowledge when choosing the extent of adrenalectomy is discussed.

Methods

A literature review was undertaken of the penetrance of the different genotypes in phaeochromocytomas, the frequency of bilateral disease and malignancy, and the underlying pathophysiological mechanisms, with emphasis on explaining the clinical phenotypes of phaeochromocytomas and their associated syndromes.

Results

Patients with bilateral phaeochromocytomas most often have multiple endocrine neoplasia type 2 (MEN2) or von Hippel–Lindau disease (VHL) with high-penetrance mutations for benign disease, whereas patients with mutations in the genes encoding SDHB (succinate dehydrogenase subunit B) or MAX (myelocytomatosis viral proto-oncogene homologue-associated factor X) are at increased risk of malignancy.

Conclusion

Adrenal-sparing surgery should be the standard approach for patients who have already been diagnosed with MEN2 or VHL when operating on the first side, whereas complete removal of the affected adrenal gland(s) is generally recommended for patients with SDHB or MAX germline mutations. Routine assessment of a patient's genotype, even after the first operation, can be crucial for adopting an appropriate strategy for follow-up and future surgery.

Dermal Hyperneury and Multiple Sclerotic Fibromas in Multiple Endocrine Neoplasia Type 2A Syndrome

Importance

Multiple endocrine neoplasia type 2 (MEN 2) syndrome is an autosomal dominant, hereditary cancer disorder caused by germline mutations in the RET (formerly MEN2A, MEN2B) proto-oncogene located on chromosomal band 10q11.21. Two distinct clinical forms have been described as the following phenotypes: multiple endocrine neoplasia type 2A (MEN 2A) and multiple endocrine neoplasia type 2B (MEN 2B) syndromes. The common and necessary nexus that defines these 2 phenotypes is the presence of medullary thyroid carcinoma (MTC). The familial MTC type of MEN 2 syndrome was included within the spectrum of MEN 2A syndrome. Cutaneous manifestations of MEN 2A syndrome include macular amyloidosis, whereas MEN 2B syndrome is traditionally linked to multiple mucosal neuromas.

Objectives

To describe a family with cutaneous manifestations not previously described in patients with MEN 2A syndrome and to discuss the association of this disorder with Cowden syndrome.

Design, Setting, and Participants

Clinicopathologic correlation of cutaneous lesions and genetic studies in 11 members of a family with familial MTC.

Interventions

Cutaneous lesions were histopathologically and immunohistochemically studied. Genetic screening for a germline mutation at the RET gene was performed in 11 family members.

Main Outcomes and Measures

Identification of cutaneous lesions not previously described in patients with MEN 2A syndrome.

Results

This family of 11 individuals with familial MTC type of MEN 2A syndrome demonstrated the moderate risk RET p.Val804Met (protein valine at residue 804 replaced by methionine) genetic mutation, with 2 of the relatives presenting with dermal hyperneury, cutaneous lesions classically described in MEN 2B syndrome, and 1 relative also showing multiple sclerotic fibromas, a cutaneous manifestation of PTEN (phosphatase and tensin homologue) hamartoma-tumor syndrome.

Conclusions and Relevance

Dermal hyperneury and multiple sclerotic fibromas should be added to the list of cutaneous manifestations of patients with the familial MTC type of MEN 2A syndrome.

Molecular genetics of syndromic and non-syndromic forms of parathyroid carcinoma

Parathyroid carcinoma (PC) may occur as part of a complex hereditary syndrome or an isolated (i.e., non-syndromic) non-hereditary (i.e., sporadic) endocrinopathy. Studies of hereditary and syndromic forms of PC, which include the hyperparathyroidism-jaw tumor syndrome (HPT-JT), multiple endocrine neoplasia types 1 and 2 (MEN1 and MEN2), and familial isolated primary hyperparathyroidism (FIHP), have revealed some genetic mechanisms underlying PC. Thus, cell division cycle 73 (CDC73) germline mutations cause HPT-JT, and CDC73 mutations occur in 70% of sporadic PC, but in only ∼2% of parathyroid adenomas. Moreover, CDC73 germline mutations occur in 20%-40% of patients with sporadic PC and may reveal unrecognized HPT-JT. This indicates that CDC73 mutations are major driver mutations in the etiology of PCs. However, there is no genotype-phenotype correlation and some CDC73 mutations (e.g., c.679_680insAG) have been reported in patients with sporadic PC, HPT-JT, or FIHP. Other genes involved in sporadic PC include germline MEN1 and rearranged during transfection (RET) mutations and somatic alterations of the retinoblastoma 1 (RB1) and tumor protein P53 (TP53) genes, as well as epigenetic modifications including DNA methylation and histone modifications, and microRNA misregulation. This review summarizes the genetics and epigenetics of the familial syndromic and non-syndromic (sporadic) forms of PC.

Genetics of Multiple Endocrine Neoplasia Type 1/Multiple Endocrine Neoplasia Type 2 Syndromes

Multiple endocrine neoplasia syndromes types 1 and 2 represent well-characterized yet clinically heterogeneous hereditary conditions for which diagnostic and management recommendations exist; genetic testing for these inherited endocrinopathies is included in these guidelines and is an important part of identifying affected patients and their family members. Understanding of these mature syndromes is challenged as more individuals undergo genetic testing and genetic data are amassed, with the potential to create clinical conundrums that may have an impact on individualized approaches to management and counseling. Clinicians who diagnose and treat patients with MEN syndromes should be aware of these possibilities.

Genotype-Phenotype Correlation in Indian Patients with MEN2-Associated Pheochromocytoma and Comparison of Clinico-Pathological Attributes with Apparently Sporadic Adrenal Pheochromocytoma

INTRODUCTION

Pheochromocytoma (PCC) manifests in up to 50% of MEN2 patients. We correlated the clinico-pathological features of MEN2-associated PCC (MEN-PCC) with RET mutations and compared them with non-MEN adrenal-PCCs.

METHODS

In this retrospective single institution study on a large PCC database (n = 208, 1997-2014) 24 MEN-PCC patients with known RET mutations were reviewed. Excluding 7 with incomplete data, the study cohort of 17 MEN-PCC patients from 11 kindreds (M:F::7:10) was identified. Clinical, biochemical, pathological attributes, and outcomes in the MEN-PCC group were correlated with the genotype, and further compared with non-MEN, apparently sporadic adrenal-PCCs (n = 132, excluding 37 extra-adrenal and 15 VHL/NF1/SDH-associated PCC).

RESULTS

Components of MEN2 encountered included MTC in 13(76.5%), Marfanoid habitus in 2, and PHPT, cutaneous lichen amyloidosis and mucosal neuromas in 1 patient each. In 11(64.7%), PCC was the first detected MEN2 component (Symptomatic:8, Incidentaloma:3). Four (23.5%) were normotensive; 8(47.1%) had bilateral PCC (7 synchronous, 1 metachronous). Surgery for PCC included laparoscopic adrenalectomy in 12; and cortical-sparing adrenalectomy in 2 of 8 bilateral PCC patients. Mean MEN-PCC tumor size was 6.9 ± 3.9 cm, and 6(35%) had additional adrenal medullary hyperplasia. Four different genotypes were encountered, commonest involving codon 634, others being 804 and 918. Mean age in MEN-PCC (27.7 ± 12.2 years) was lower than non-MEN PCC (39.4 ± 15.7, p = 0.018). Proportion of pediatric patients (35.3% in MEN-PCC vs. 12.9% in non-MEN-PCC, p = 0.007), bilateral tumors (47.1% in MEN-PCC, 4.5% in non-MEN-PCC, p < 0.001), and adrenal medullary hyperplasia (35.2% in MEN-PCC, 0.7% in non-MEN-PCC, p < 0.001) were different. Median 24-hour urinary metanephrines was significantly higher in index MEN-PCC patients, than non-MEN-PCC (634 vs. 214 mcg/24 h, p value = 0.006), but was non-significantly higher in non-index MEN-PCC patients. Mean tumor sizes were comparable in the two groups. None of MEN-PCC patients had malignant PCC, compared to 7(5.3%) in non-MEN-PCC.

CONCLUSIONS

In this cohort of MEN-PCC from India, the commonest causative RET mutations for MEN-PCC involved codon 634. MEN-PCC patients were younger, and more frequently had bilateral PCC than non-MEN disease. MEN-PCC patients in India are diagnosed with large tumors and extremely high catecholamine/metanephrine levels.

Oral mucosal stigmata in hereditary-cancer syndromes: From germline mutations to distinctive clinical phenotypes and tailored therapies

Numerous familial tumor syndromes are associated with distinctive oral mucosal findings, which may make possible an early diagnosis as an efficacious marker for the risk of developing visceral malignancies. In detail, Familial Adenomatous Polyposis (FAP), Gardner syndrome, Peutz-Jeghers syndrome, Cowden Syndrome, Gorlin Syndrome, Lynch/Muir-Torre Syndrome and Multiple Endocrine Neoplasia show specific lesions of the oral mucosa and other distinct clinical and molecular features. The common genetic background of the above mentioned syndromes involve germline mutations in tumor suppressor genes, such as APC, PTEN, PTCH1, STK11, RET, clearly implied in both ectodermal and mesodermal differentiation, being the oral mucosal and dental stigmata frequently associated in the specific clinical phenotypes. The oral and maxillofacial manifestations of these syndromes may become visible several years before the intestinal lesions, constituting a clinical marker that is predictive for the development of intestinal polyps and/or other visceral malignancies. A multidisciplinary approach is therefore necessary for both clinical diagnosis and management of the gene-carriers probands and their family members who have to be referred for genetic testing or have to be investigated for the presence of visceral cancers.

Diversity of mutations in the RET proto-oncogene and its oncogenic mechanism in medullary thyroid cancer

Thyroid cancer is the most common endocrine malignancy and accounts for nearly 1% of all of human cancer. Thyroid cancer has four main histological types: papillary, follicular, medullary, and anaplastic. Papillary, follicular, and anaplastic thyroid carcinomas are derived from follicular thyroid cells, whereas medullary thyroid carcinoma (MTC) originates from the neural crest parafollicular cells or C-cells of the thyroid gland. MTC represents a neuroendocrine tumor and differs considerably from differentiated thyroid carcinoma. MTC is one of the aggressive types of thyroid cancer, which represents 3-10% of all thyroid cancers. It occurs in hereditary (25%) and sporadic (75%) forms. The hereditary form of MTC has an autosomal dominant mode of inheritance. According to the present classification, hereditary MTC is classified as a multiple endocrine neoplasi type 2 A & B (MEN2A & MEN2B) and familial MTC (FMTC). The RET proto-oncogene is located on chromosome 10q11.21. It is composed of 21 exons and encodes a transmembrane receptor tyrosine kinase. RET regulates a complex network of signal transduction pathways during development, survival, proliferation, differentiation, and migration of the enteric nervous system progenitor cells. Gain of function mutations in RET have been well demonstrated in MTC development. Variants of MTC result from different RET mutations, and they have a good genotype-phenotype correlation. Various MTC related mutations have been reported in different exons of the RET gene. We proposed that RET genetic mutations may be different in distinct populations. Therefore, the aim of this study was to find a geographical pattern of RET mutations in different populations.

Pediatric Medullary Thyroid Carcinoma

Medullary thyroid carcinoma (MTC), which originates from thyroid parafollicular C cells, accounts for 3 to 5% of thyroid malignancies. MTC occurs either sporadically or in an inherited autosomal dominant manner. Hereditary MTC occurs as a familial MTC or as a part of multiple endocrine neoplasia (MEN) type 2A and B syndromes. A strong genotype-phenotype correlation has been observed between hereditary MTC and germ-line "gain of function" mutations of the RET proto-oncogene. Most cases of pediatric MTC are hereditary whereas sporadic MTC is rare in children and is usually diagnosed in adults. Therefore, MTC in children is most often diagnosed in the course of a familial genetic investigation. The standard treatment of MTC mainly requires surgery involving total thyroidectomy and central neck node dissection before extrathyroidal extension occurs. To prevent MTC development in hereditary syndromes, prophylactic thyroidectomy is performed in presymptomatic patients. An appropriate age at which the surgery should take place is determined based upon the data from genotyping, serum calcitonin measurements, and ultrasonography. For the treatment of advanced MTC cases, the broad spectrum receptor tyrosine kinase inhibitors vandetanib and cabozantinib, which also inhibit RET, are used although they are not always effective.

A novel RET gene mutation in a patient with apparently sporadic pheochromocytoma

Pheochromocytoma (Pheo) is a chromaffin tumor arising from the adrenal medulla. The recent discovery of new germline mutations in RET, SDHA, SDHB, SDHC, SDHD, VHL, NF1, TMEM127, MAX genes, increased the rate of genetic disease from 10% to 28% in patients with apparently sporadic tumor. RET germline mutations cause multiple endocrine neoplasia type 2 syndrome (MEN 2A) characterized by complete penetrance of medullary thyroid cancer (MTC), and lower prevalence of Pheo and hyperparathyroidism. We describe the genetic etiology of an apparently sporadic case of monolateral Pheo in a 42-year-old male patient. A new (not previously reported) MEN 2A-associated germline RET mutation located in exon 11 (Glu632Gly, caused by an A>G point mutation at position 1895 of the RET cDNA) was found in the patient but not in his living first-degree relatives. This observation increases the number of possible germline RET mutations. Genotype-phenotype correlation of this new genetic alteration is unknown, but this rare mutation is probably associated with a low risk for MTC (usually the first tumor diagnosed in MEN 2A syndrome) and with the development of Pheo before the onset of MTC. Since we expect MTC to occur in our patient, strict follow-up is mandatory. Our findings emphasize the relevance of genetic testing in patients with Pheo, especially when the clinical presentation (family history, young age at diagnosis, multiple locations, malignant lesions, and bilateralism) is suggestive.

A NOVEL DOUBLE MUTATION VAL648ILE AND VAL804LEU OF RET PROTO-ONCOGENE IN MULTIPLE ENDOCRINE NEOPLASIA TYPE 2

OBJECTIVE

We report the case of a female patient with multiple endocrine neoplasia type 2A (MEN2A) who was found to have a double mutation in the RET (rearranged during transfection) proto-oncogene.

METHODS

RET mutational analysis was performed by Sanger DNA sequencing.

RESULTS

The proband was a compound heterozygote for the RET germline mutations Val648Ile and Val804Leu on exons 11 and 14, respectively. Genetic analysis of family members showed the presence of the Val648Ile mutation in all except 1 daughter who carried the Val804Leu mutation. However, none of them showed any clinical, biochemical, or histologic signs of neoplastic disease either in the thyroid or adrenal gland. Furthermore, a daughter and the proband's sister who underwent a prophylactic thyroidectomy did not show pathologic evidence of C-cell disease.

CONCLUSIONS

We hypothesize that the combined effect of the 2 mutations may have induced the development of pheochromocytoma (PHEO) in our patient. Thus, in the presence of single RET-induced mild medullary thyroid cancer (MTC) phenotype, the search for additional genetic anomalies may lead to the discovery of rare but potentially more aggressive double mutation genotypes.

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.

Beneficial Effects of the mTOR Inhibitor Everolimus in Patients with Advanced Medullary Thyroid Carcinoma: Subgroup Results of a Phase II Trial

Objective. Until recently, advanced medullary thyroid cancer (MTC) had few treatment options except surgery. The mTOR inhibitor everolimus has shown encouraging results in neuroendocrine tumors. As part of a prospective phase II study, we analyzed the safety and efficacy of everolimus in advanced MTC. Methods. Seven patients with per RECIST 1.1 documented advanced MTC were included and received everolimus 10 mg daily. The primary objective was determining treatment efficacy. Secondary endpoints included progression-free survival (PFS), overall survival (OS), toxicity, and pharmacokinetics (PK). Results. Median follow-up duration was 28 weeks (17-147). Five patients (71%) showed SD, of which 4 (57%) showed SD >24 weeks. Median PFS and OS were 33 (95%CI: 8-56) and 30 (95%CI: 15-45) weeks, respectively. Toxicity was predominantly grade 1/2 and included mucositis (43%), fatigue (43%), and hypertriglyceridemia (43%). Four MTCs harbored the somatic RET mutation c.2753T>C, p.Met918Thr. The best clinical response was seen in a MEN2A patient. PK characteristics were consistent with phase I data. One patient exhibited extensive toxicity accompanying elevated everolimus plasma concentrations. Conclusions. This study suggests that everolimus exerts clinically relevant antitumor activity in patients with advanced MTC. Given the high level of clinical benefit and the relatively low toxicity profile, further investigation of everolimus in these patients is warranted.

Hereditary Medullary Thyroid Cancer Genotype-Phenotype Correlation

During the last two decades, there has been a marked expansion of our knowledge of both the basic and clinical aspects of multiple endocrine neoplasia type 2 (MEN2). There are two clinically distinct types of MEN2 syndrome, termed MEN2A and MEN2B. Within MEN2A, there are four variants: (i) classical MEN2A, represented by the uniform presence of MTC and the less frequent occurrence of pheochromocytoma, or primary hyperparathyroidism, or both; (ii) MEN2A with cutaneous lichen amyloidosis; (iii) MEN2A with Hirschsprung's disease; and (iv) familial medullary thyroid carcinoma (FMTC), i.e., families or individuals with only MTC. MEN2B is associated with MTC, pheochromocytoma, and mucosal neuromas. Hereditary MTC is caused by autosomal dominant gain of function mutations in the RET proto-oncogene. Specific RET mutations may suggest a predilection toward a particular phenotype and clinical course with a strong genotype-phenotype correlation. Based upon these genotype-phenotype correlations, RET mutations are now stratified into three risk levels, i.e., highest, high, and moderate risk, based on the penetrance and aggressiveness of the MTC. Children in the highest risk category should undergo thyroidectomy in their first year of life, and perhaps even in their first months of life. Children in the high-risk category should have ultrasound of the neck and calcitonin (CTN) measurement performed prior to thyroidectomy. Thyroidectomy should typically be performed at the age of 5 or earlier, depending on the presence of elevated serum CTN levels. However, heterogeneity in disease expression and progression within these groups varies considerably. To personalize disease management, the decision regarding the age of prophylactic thyroidectomy is no longer based upon genotype alone but is currently driven by additional clinical data, the most important being serum CTN levels; specifically, the decision to perform thyroidectomy should err on the safe side if the CTN level is elevated but below 30 pg/ml, especially in the moderate risk group. Personalized management also includes decisions about the best age to begin biochemical screening for pheochromocytoma and primary hyperparathyroidism.

Article Commentary: Medullary Thyroid Cancer: An Update for Surgeons

Medullary thyroid carcinoma is uncommon but accounts for approximately 4 to 5 per cent of all thyroid cancers. Although most cases are sporadic, close to one-fourth of cases result from germline mutations in the RET proto-oncogene. These mutations are clinically important because they predict the earliest age of medullary thyroid cancer diagnosis and clinical aggressiveness, which guide individualized management. This review covers the presentation, diagnosis, workup, current management, and future directions of the management of medullary thyroid carcinoma. Today's chance for cure depends on early and appropriate surgical resection. Further investigation of the cellular signaling pathways shown to be essential for the growth and spread of medullary thyroid carcinoma remains an active field with hope for providing targeted systemic therapy for patients with progressive disease.

Diagnosis and preoperative imaging of multiple endocrine neoplasia type 2: current status and future directions

Multiple endocrine neoplasia type 2 (MEN2) is a rare autosomal dominant syndrome caused by mutations in the RET protooncogene and is characterized by a strong penetrance of medullary thyroid carcinoma (all subtypes) and is often accompanied by pheochromocytoma (MEN2A/2B) and primary hyperparathyroidism (MEN2A). The evaluation and management of MEN2-related tumours is often different from that of sporadic counterparts. This review article provides an overview of clinical manifestations, diagnosis and surgical management of MEN2 patients. This review also presents applications of the most up-to-date imaging modalities to MEN2 patients that are tightly linked to the clinical management and aims to guide physicians towards a rationale for the use of imaging prior to prophylactic thyroidectomy, initial surgery and reoperations for persistent/recurrent disease. This review also concludes that, in the near future, it is expected that these patients will indeed benefit from newly developed positron emission tomography approaches which will target peptide receptors and protein kinases. Identification of MEN2-specific radiopharmaceuticals will also soon arise from molecular profiling studies. Furthermore, subtotal (cortical-sparing) adrenalectomy, which is a valid option in MEN2 for avoiding long-term steroid replacement, will benefit from an accurate estimation through imaging of differential adrenocortical function.

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.

Diagnosis and surgical treatment of multiple endocrine neoplasia type 2A

BACKGROUND

This study aims to introduce the diagnosis and surgical treatment of the rare disease multiple endocrine neoplasia type 2A (MEN 2A).

METHODS

Thirteen cases of MEN 2A were diagnosed as medullary thyroid carcinoma (MTC) and pheochromocytoma by biochemical tests and imaging examination. They were treated by bilateral adrenal tumor excision or laparoscopic surgery.

RESULTS

Nine patients were treated by bilateral adrenal tumor excision and the remaining four were treated by laparoscopic surgery for pheochromocytoma. Ten patients were treated by total thyroidectomy and bilateral lymph nodes dissection and the remaining three were treated by unilateral thyroidectomy for MTC. Up to now, three patients have died of MTC distant metastasis.

CONCLUSIONS

We confirmed that MEN 2A can be diagnosed by biochemical tests and imaging examination when genetic testing is not available. Surgical excision is the predominant way to treat MEN 2A; pheochromocytoma should be excised at first when pheochromocytoma and MTC occur simultaneously.

A differential diagnosis of inherited endocrine tumors and their tumor counterparts

Inherited endocrine tumors have been increasingly recognized in clinical practice, although some difficulties still exist in differentiating these conditions from their sporadic endocrine tumor counterparts. Here, we list the 12 main topics that could add helpful information and clues for performing an early differential diagnosis to distinguish between these conditions. The early diagnosis of patients with inherited endocrine tumors may be performed either clinically or by mutation analysis in at-risk individuals. Early detection usually has a large impact in tumor management, allowing preventive clinical or surgical therapy in most cases. Advice for the clinical and surgical management of inherited endocrine tumors is also discussed. In addition, recent clinical and genetic advances for 17 different forms of inherited endocrine tumors are briefly reviewed.