Presymptomatic thyroidectomy in multiple endocrine neoplasia 2a

Multiple Endocrine Neoplasia: A Genetically Diverse Group of Familial Tumor Syndromes

Multiple endocrine neoplasia (MEN) syndrome is a familial cancer syndrome characterized by neuroendocrine tumors. The syndrome encompasses four major subtypes: MEN1, MEN2A, MEN2B, and MEN4. MEN1 is caused by mutations in the MEN1 gene, MEN2A and MEN2B are caused by mutations in RET, and MEN4 is caused by mutations in CDKNB1. All are inherited in an autosomal dominant pattern, but de novo cases do arise. While all subtypes are associated with neuroendocrine tumors, each has characteristic organ involvement. Identifying patients with the syndrome can aid in proper screening and treatment.

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.

Prevalence by age and predictors of medullary thyroid cancer in patients with lower risk germline RET proto-oncogene mutations

BACKGROUND

Age-related risk of medullary thyroid carcinoma (MTC) development in presymptomatic carriers of lower risk germline RET mutations is uncertain; such data may aid counseling patients regarding timing of thyroidectomy.

METHODS

From an institutional database and an exhaustive literature review, we identified 679 patients with American Thyroid Association (ATA) level A or B mutations who were identified because of family screening (index cases of MTC were excluded to minimize selection bias). We evaluated age at thyroidectomy or last evaluation if no thyroidectomy, preoperative calcitonin level (elevated or not), the mutated codon, and outcome (MTC vs. no MTC after thyroidectomy or no clinical evidence of MTC if thyroid intact). Data were used to estimate the cumulative prevalence of MTC and/or assess likelihood of MTC stratified by codon. After exclusion of cases with missing data or small representation, 503 patients with mutations in codons 533, 609, 611, 618, 620, 791, and 804 were analyzed.

RESULTS

236 patients had MTC. Cumulative prevalence and median time to MTC varied by codon and within ATA risk levels (p<0.0001). Patients with a codon 620 mutation were 2.8-6.9 times more likely to have MTC than other level B mutation carriers, and 5.1-21.7 times more likely than level A mutation carriers included in our focus population. The youngest median time to MTC was 19 years for codon 620 and the oldest was 56 years for codon 611. Cumulative prevalence of MTC by age 20 was 10% or lower for codons 533, 609, 611, 791, and 804. By age 50, it ranged from 18% for codon 791 to 95% for codon 620. An elevated preoperative calcitonin level strongly predicted MTC on final pathology, though false-negative rates varied by codon (p<0.0001). Positive predictive values ranged from 76% to 100% by codon with an overall positive predictive value of 87% across codons.

CONCLUSIONS

This study offers a better understanding of the age-related development of MTC in lower risk RET mutation carriers, provides evidence of further distinctions between lower risk mutations within ATA subgroups, and clarifies the clinical significance of codon 791 mutations. The data support individualized "codon-based" management approaches coupled with clinical data such as calcitonin levels.

Pediatric ethics guidelines for hereditary medullary thyroid cancer

Hereditary medullary thyroid cancer is an aggressive cancer for which there is no standard effective systemic therapy, but which can be prevented through genetic screening and prophylactic thyroidectomy. Although this cancer accounts for roughly 17% of all pediatric thyroid cancers, a significant percentage of affected families do not "accept" screening, while many gene carriers delay or refuse prophylactic thyroid surgery for their children. Current genetic screening practices in medullary thyroid cancer are inadequate; more than 50% of index patients with hereditary medullary thyroid cancer present with a thyroid mass; up to 75% have distant metastasis. These proposed pediatric ethics guidelines focus on two ethical issues that affect at-risk children: (1) how do we identify at-risk children whose RET-positive relative refuses to disclose that they carry the mutation? (2) How do we protect RET-positive children whose parents refuse prophylactic thyroidectomy?

Prophylactic thyroidectomy in multiple endocrine neoplasia type 2

Medullary thyroid carcinoma (MTC) is the main component of the autosomal dominant cancer syndrome multiple endocrine neoplasia type 2 (MEN 2). MEN 2 is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene. In RET-mutation carriers, an age-related progression has been documented from normal C-cells to premalignant C-cell hyperplasia and finally to MTC with or without cervical lymph node metastases. The time required for this neoplastic development as well as penetrance and aggressiveness of disease mainly depends on the specific RET mutation with a strong genotype-phenotype correlation. Recommendations for the timing of prophylactic thyroidectomy are based upon a model that utilizes these genotype-phenotype correlations to stratify mutations into four risk levels. The excellent prognosis for MTC diagnosed at its earliest stage underscores the importance of early diagnosis by RET-mutation analysis for hereditary MTC.

Molecular alterations in hereditary and sporadic thyroid and parathyroid diseases

Thyroid and parathyroid diseases are fairly common and can be either hereditary or sporadic in nature. Tumors and tumor-like processes account for the majority of surgical pathology specimens in both of these endocrine organs. Molecular alterations are well known to occur in both the hereditary and the sporadic settings, and include alterations in tumor suppressor genes and oncogenes. The genetic pathways of tumors of parathyroid and thyroid are beginning to be well understood and are proving to be useful diagnostic, prognostic, and potential therapeutic targets. The molecular alterations in parathyroid and thyroid tumors and tumor-like processes are reviewed, with a focus on the potentially clinically useful diagnostic markers.

Thyroid cancer in children

In 1996, the authors were asked to review the subject of thyroid cancer in children. Over the subsequent decade, much has been learned about the treatment and outcome of these uncommon tumors. We now recognize quantitative and perhaps qualitative differences in genetic mutations and growth factor expression patterns in childhood thyroid cancers compared with those of adults. We also know that thyroid cancers induce a robust immune response in children that might contribute to their longevity. Patients under 10 years of age probably represent a unique subset of children at particularly high risk for persistent or recurrent disease; the management of these patients is under evaluation. We remain limited in our knowledge of how to stratify children into low- and high-risk categories for appropriate long-term follow-up and in our knowledge of how to treat children who have detectable serum thyroglobulin but negative imaging studies. In this article, the authors update our understanding of thyroid cancers in children with special emphasis on how these data relate to the current guidelines for management of thyroid cancer developed by the American Thyroid Association Taskforce. The limited data regarding management of children who have detectable serum thyroglobulin but negative whole-body scans are also reviewed.

RET and neuroendocrine tumors

The RET proto-oncogene encodes a receptor tyrosine kinase that is a main component of the signaling pathway activated by the glial cell line-derived neurotrophic factor family ligands. Gene targeting studies revealed that signaling through RET plays a crucial role in neuronal and renal organogenesis. It is well-known that germline mutations in RET lead to the human inherited diseases, multiple endocrine neoplasia type 2 (MEN 2) and Hirschsprung's disease, and that somatic rearrangements of RET cause papillary thyroid carcinoma. Due to marked advances in understanding of the molecular mechanisms of the development of MEN 2, a consensus on MEN 2 management associated with RET status is being reached and currently put into general use as a guideline. In this review, we summarize progress in the study of RET from bench to bedside, focusing on pathophysiology of neuroendocrine tumors.