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

C634Y mutation in RET-induced multiple endocrine neoplasia type 2A: A case report

BACKGROUND

Multiple endocrine neoplasia type 2 (MEN2) is a rare, autosomal dominant endocrine disease. Currently, the RET proto-oncogene is the only gene implicated in MEN2A pathogenesis. Once an RET carrier is detected, family members should be screened to enable early detection of medullary thyroid carcinoma, pheochromocytoma, and hyperparatitity. Among these, medullary thyroid carcinoma is the main factor responsible for patient mortality. Accordingly, delineating strategies to inform clinical follow-up and treatment plans based on genes is paramount for clinical practitioners.

CASE SUMMARY

Herein, we present RET proto-oncogene mutations, clinical characteristics, and treatment strategies in a family with MEN2A. A family study was conducted on patients diagnosed with MEN2A. DNA was extracted from the peripheral blood of family members, and first-generation exon sequencing of the RET proto-oncogene was conducted. The C634Y mutation was identified in three family members spanning three generations. Two patients were sequentially diagnosed with pheochromocytomas and bilateral medullary thyroid carcinomas. A 9-year-old child harboring the gene mutation was diagnosed with medullary thyroid carcinoma. Surgical resection of the tumors was performed. All family members were advised to undergo complete genetic testing related to the C634Y mutation, and the corresponding treatments administered based on test results and associated clinical guidelines.

CONCLUSION

Advancements in MEN2A research are important for familial management, assessment of medullary thyroid cancer invasive risk, and deciding surgical timing.

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.

Serum calcitonin reference values for calcium stimulation tests by electrochemiluminescence immunoassay in Japanese men with non-medullary thyroid carcinoma

PURPOSE

Calcitonin is the most sensitive tumor marker of medullary thyroid carcinoma (MTC) and a calcium stimulation test is used to improve this sensitivity. In Japan, the electrochemiluminescence immunoassay (ECLIA) is currently the only test performed to measure serum calcitonin. There is a gender difference in the reference value of serum calcitonin; however, a reference upper limit for use with ECLIA has been reported only for women, but not for men.

METHODS

We conducted the calcium stimulation test using ECLIA in 21 men with non-medullary thyroid carcinoma (non-MTC), before and after total thyroidectomy.

RESULTS

Preoperatively, the basal calcitonin values were within normal limits in all patients. They increased to a mean value of 37.6 pg/mL after calcium stimulation, and we calculated that the reference upper limit was 83.7 pg/mL. The stimulation test results after total thyroidectomy showed undetectable basal and stimulated calcitonin values in every patient (<0.5 pg/mL).

CONCLUSIONS

To our knowledge, this is the first study to calculate reference values for this stimulation test using an ECLIA in men with non-MTC. We propose that men can be regarded as biochemically cured or as having normal serum calcitonin values when the stimulated calcitonin values obtained by ECLIA are <83.7 pg/mL before and <0.5 pg/mL after total thyroidectomy.