Very early prophylactic thyroid surgery for infants with a mutation of the RET proto-oncogene at codon 634: evaluation of the implementation of international guidelines for MEN type 2 in a single centre

Late-Onset Medullary Thyroid Cancer in a Patient with a Germline RET Codon C634R Mutation

Background: Multiple endocrine neoplasia type 2A (MEN2A) is a rare, hereditary syndrome resulting from a germline mutation in the RET proto-oncogene and characterized primarily by medullary thyroid cancer (MTC), pheochromocytoma (PHEO), and hyperparathyroidism. Types of RET mutation have been associated with age at onset, clinical outcomes of MTC, and the penetrance of other components. Patients classified as 'high-risk' by the American Thyroid Association (ATA), based on the aggressiveness of MTC and the penetrance of other components, are recommended to undergo early prophylactic thyroidectomy at age ≤ 5 years and to be screened for PHEO at age ≥ 11 years. Patients with RET codon C634R mutations have been classified as high-risk. Case presentation: The present study describes a 71-year-old woman newly diagnosed with hereditary MTC related to a RET C634R germline mutation. Her basal serum calcitonin level was high, but there was no evidence of distant metastases. Surgery revealed bilateral MTC with two metastatic lymph nodes. Because microscopic resection was incomplete and extranodal extension was observed, the patient underwent adjuvant external beam radiotherapy. Response to therapy was excellent. Follow-up after 1.5 years showed no evidence of disease or other manifestations of MEN2A. Conclusion: Despite RET C634R carriers being classified as high-risk by the ATA, this patient did not present with either distant MTC or PHEO until her seventies. To our knowledge, only one other patient has shown a similar late identification of a RET C634R mutation, but MTC could not be diagnosed because the patient was lost to follow-up. Further research is required to develop optimal protocols that could allow patients requiring prophylactic thyroidectomy to be differentiated from those who can be monitored closely without early surgery.

Role of preoperative basal calcitonin levels in the timing of prophylactic thyroidectomy in patients with germline RET mutations

BACKGROUND

The American Thyroid Association (ATA) published recommendations for the timing of prophylactic surgery for medullary thyroid carcinoma based on the specific mutation, patient age, family history, and serum calcitonin levels. The aim of this study was to assess the role of preoperative basal calcitonin (prebCt) levels in predicting the presence of medullary carcinoma of the thyroid in patients with RET mutations.

METHODS

We conducted a retrospective study in two endocrine surgery departments. Between 1986 and 2012, a total of 32 patients with RET mutations underwent prophylactic thyroidectomy. The patients were stratified into four ATA risk levels: A, B, C, and D.

RESULTS

All of the patients were biologically cured. Microcarcinoma was observed in the final pathology report for four of the 20 patients with normal prebCt (25 %) and for nine of the 12 patients with elevated prebCt (75 %). In the level A group, four patients with normal prebCt and one patient with elevated prebCt presented with microcarcinoma. In the level C group, one patient with normal prebCt and six of the seven patients with elevated prebCt (86 %) presented with microcarcinoma.

CONCLUSIONS

PrebCt can predict the presence of microcarcinoma according to surgical pathological analysis. Patients with microcarcinoma can be biochemically and clinically cured using prophylactic thyroidectomy.

Medullary thyroid cancer in a 9-week-old infant with familial MEN 2B: Implications for timing of prophylactic thyroidectomy

BACKGROUND

Patients with Multiple Endocrine Neoplasia type 2 (MEN 2) are at high risk of developing aggressive medullary thyroid carcinoma (MTC) in childhood, with the highest risk in those with MEN type 2B (of whom >95% have an M918T RET proto-oncogene mutation). Metastatic MTC has been reported as young as 3 months of age. Current guidelines recommend prophylactic thyroidectomy within the first year of life for MEN 2B.

PATIENT FINDINGS

We report a 9-week-old infant with MTC due to familial MEN 2B. A full-term male infant, born to a mother with known MEN 2B and metastatic MTC, had an M918T RET proto-oncogene mutation confirmed at 4 weeks of age. He underwent prophylactic total thyroidectomy at 9 weeks of age. Pathology showed a focal calcitonin-positive nodule (2.5 mm), consistent with microscopic MTC.

SUMMARY

This case highlights the importance of early prophylactic thyroidectomy in MEN 2B. Although current guidelines recommend surgery up to a year of life, MTC may occur in the first few weeks of life, raising the question of how early we should intervene. In this report, we discuss the risks, benefits and barriers to performing earlier thyroidectomy, soon after the first month of life, and make suggestions to facilitate timely intervention. Prenatal anticipatory surgical scheduling could be considered in familial MEN 2B. Multidisciplinary collaboration between adult and pediatric specialists is key to the optimal management of the infant at risk.

Coincidence of multiple endocrine neoplasia type 2A with acromegaly

Medullary thyroid carcinoma (MTC) occurs as a part of multiple endocrine neoplasia (MEN) type 2. Acromegaly, a pituitary adenoma, occurs as a part of MEN1. Rarely, MEN2 and MEN1 coexist in a single patient simultaneously. A 40-year-old man with a history of pituitary adenomectomy for acromegaly had a surgical resection of thyroid carcinoma clinically diagnosed as MTC. His mother, who had MTC and pheochromocytoma, had a germline mutation in the RET gene that could cause the subtype, MEN2A. Identification of gene mutations in RET and MEN1 were examined in the subject. The resected tumor was pathologically diagnosed as MTC. Genomic examinations revealed the RET mutation C634F, which was identical to the mutation of his mother, but no MEN1 gene mutation was found. Although the simultaneous occurrence of both MEN2A and sporadic acromegaly may be accidental, there is evidence to suggest a genetic interaction between MEN2 and acromegaly.

Role of RET codonic mutations in the surgical management of medullary thyroid carcinoma in pediatric age multiple endocrine neoplasm type 2 syndromes

PURPOSE

Hereditary medullary thyroid carcinoma (MTC) therapy is surgical resection. Because the genetic screening was available, the early diagnosis of the disease has been possible. The purpose of this study was to evaluate the role of the genetic test in the management of these children and to draw some information about the surgical timing.

METHODS

Thirteen patients underwent total thyroidectomy at our institute between 1995 and 2007. Seven patients underwent a curative thyroidectomy, and 6 patients underwent a prophylactic thyroidectomy. Two patients were operated with a minimally invasive video-assisted technique. We studied the following parameters: age, risk level associated to the RET gene mutations, aim of surgery (curative or prophylactic), tumor histopathologic features, lymph node involvement, and distal metastases.

RESULTS

We found a statistical association between cancer maximum diameter and some parameters analyzed: age of patients, aim of surgery, single or multifocal MTC, and number of organs involved by distal metastases. Cancer diameter at the moment of diagnosis seems to increase according to the aggressiveness of RET gene mutation found.

CONCLUSIONS

The best strategy to cure MTC is to prevent it. Genetic screening could be a fundamental tool in the management of multiple endocrine neoplasm type 2 children. An improvement of scientific knowledge regarding RET gene alterations and an early and appropriate use of genetic tests could allow a better understanding of the correct surgical timing and a wider use of less aggressive surgical procedures.

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.

Genotype-phenotype based surgical concept of hereditary medullary thyroid carcinoma

BACKGROUND

Since DNA tests have enabled reliable identification of asymptomatic RET (rearranged during transfection) gene carriers, myriads of publications have appeared on genotype-phenotype relationships. A comprehensive appraisal of this body of evidence using evidence-based methodology is pending.

METHODS

This study was based on systematic evaluation of the literature using evidence-based criteria.

RESULTS

(1) There is a distinct age-related progression of hereditary medullary thyroid carcinoma (MTC) in carriers of RET mutations (grade C). (2) Among the high-risk RET mutations, those in codon 634 cause higher penetrance rates of the multiple endocrine neoplasia 2A phenotype (MTC, pheochromocytoma, and parathyroid hyperplasia/adenoma) than mutations in codons 609, 611, 618, and 620, irrespective of the amino acid substituting for cysteine (grade C). (3) DNA-based screening is superior to calcitonin-based screening in asymptomatic RET carriers (grade C). (4) Using a worst-case scenario, i.e., considering the earliest finding of MTC in asymptomatic RET carriers, pre-emptive thyroidectomy should be performed before that time (grade C) to be truly prophylactic. Specifically, for carriers of highest-risk mutations (codon 918): within the first year of life; for carriers of high-risk mutations (codon 609, 611, 618, 620, 630, and 634): before the age of 5 years; and for carriers of least-high risk mutations (codon 768, 790, 791, 804, and 891): before the age of 5-10 years. Strict adherence to these grade C recommendations can result in undertreatment of the former (codon 634) and overtreatment of the latter.

CONCLUSIONS

These genotype-phenotype correlations provide a solid foundation on which to base surgical concepts, leaving little room for randomized controlled clinical trials.

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.