A Calcitonin-Negative Neuroendocrine Tumor Derived from Follicular Lesions of the Thyroid

Neuroendocrine lesions of the thyroid are rare. The most common types are medullary thyroid carcinomas (MTCs) and C-cell hyperplasia. MTCs originate from thyroid parafollicular cells that secrete calcitonin which serves as a serum marker of MTCs. Here, the rare case of a calcitonin-negative neuroendocrine tumor (NET) derived from follicular lesions of the thyroid is described. A 34-year-old man presented at our hospital for the surgical management of an incidental thyroid nodule that was observed on an ultrasound sonography (USG) of the neck. Initially, USG-guided aspiration cytology was performed, and a MTC was suspected. The expressions of thyroglobulin and thyroid transcription factor-1, which are thyroid follicular cell markers, and synaptophysin and chromogranin A, which are neuroendocrine markers, was confirmed following surgical pathology. However, the staining of calcitonin, a marker of MTCs, was not observed. A nonmedullary NET of the thyroid is uncommon, and the distinction between calcitonin-negative NETs and MTCs of the thyroid may be important due to differences in their clinical courses and management.

[Clinical significance and cost-benefit analysis of serum calcitonin assay in diagnosis and treatment of medullary thyroid carcinoma]

Objective: To study the clinical significance of serum calcitonin in the diagnosis and treatment of medullary thyroid carcinoma and to analyze its cost-benefit. Methods: One hundred and forty one patients with medullary thyroid carcinoma who undertook calcitonin test and frozen pathological examination were enrolled in this study from Oct 2012 to Mar 2018. Using the method of χ(2) test, the positive rate of calcitonin test and frozen pathological examination in diagnosis of medullary thyroid carcinoma(MTC) were compared. Firstly, we compared the correct checkout cost of calcitonin test and that of frozen pathological examination (total number of patients×cost of examination/the correctly detected number of patients) . Secondly, we calculated whether calcitonin test help patients save money(average cost of treatment in hospital for MTC×number of patients who were evaluated to be candidate for surgery-cost of calcitonin test×total number of patients)/total number of patients. Results: 139 patients were positive in calcitonin test among 141 patients, and the positive rate was 98.58%. 91 patients were positive in frozen pathological examination, and the positive rate was 64.54% (χ(2)=97.821, P<0.000 1) . Cost-benefit analysis showed that the correct checkout cost of calcitonin test and frozen pathological examination were 71.01 yuan and 426.10 yuan, also,1 371 938.64 yuan could be saved totally and 9 730.06 yuan could be saved per patient because of calcitonin test. Conclusion: Serum calcitonin test had a significant effect on the diagnosis and treatment of medullary thyroid carcinoma and was economical and practical.

[Efficacy and safety of vandetanib on advanced medullary thyroid carcinoma: single center result from a phase Ⅲ study]

Objective: There is no effective therapy for patients with advanced medullary thyroid carcinoma (MTC). Vandetanib,a novel multitargeted receptor tyrosine kinase inhibitor, has previously shown antitumor activity in phase Ⅱ studies of patients with advanced MTC. This study was to evaluate the efficacy and the safety of vandetanib on advanced MTC. Methods: This study was an open, international multi-center phase Ⅲ clinical trial and the study number was NCT01298323. The single-center study was a sub-group analysis of the international study, which was conducted on 9 pathologically confirmed advanced MTC patients by Cancer Hospital Chinese Academy of Medical Sciences between March 2012 and October 2017. Vandetanib (300 mg) was orally administered daily till death or withdrawal. The efficacy was evaluated according to RECIST criteria and the adverse events were evaluated according to NCI criteria. Results: The objective response rate was 3/9,and the disease control rate was 4/9. The median progression-free survival was 44 months. All patients who had the elevated levels of calcitonin (CTN) and carcino-embryonic antigen (CEA) before treatment began to show the decreases in the level of CTN and CEA after 3 months and later showed again the increases in the levels of both tumor markers with tumor progression. By ROC curve analysis, CTN was of statistically significance(P<0.05, 95%CI 0.558-0.834), but CEA was not(P>0.05). Adverse events were generally mild (grade 1 or 2),including hypertension (9 cases),skin rash (9 cases), and diarrhea (6 cases). Two patients developed grade 3 elevation of serum glutamate pyruvate transaminase and one patient developed grade 3 elevation of drug-related bowel disease. No grade 4 drug-related adverse event occurred. Conclusions: Vandetanib is effective and well tolerated for patients with locally advanced or metastatic MTC who have no chance for surgery. This indicates the increase of CTN is clinically relevant to disease progression, but the number of patients are extremely low, and, therefore further research is needed. Long-term use of vandetanib may cause resistance.

Characteristics of RET gene mutations in Vietnamese medullary thyroid carcinoma patients: a single-center analysis

BACKGROUND

The RET gene point mutation is the main molecular alteration involved in medullary thyroid carcinoma (MTC) tumorigenesis. Previous studies in Vietnam mainly consisted of case reports, with limited data on larger sample sizes. In this study, we investigated RET gene mutations in exons 10, 11, and 16 and analyzed clinicopathological features of a series of Vietnamese MTC patients.

METHODS

We collected 33 tissue samples from patients with MTC and analyzed RET mutations using the Sanger sequencing method. The relationship between hotspot RET mutations (exons 10, 11, 16) and clinicopathological features were investigated.

RESULTS

Among the 33 analyzed cases, 17 tumors (52%) harbored RET mutations in exon 10, 11, or 16. A total of 10 distinct genetic alterations were identified, including eight missense mutations and two short indels. Of these, seven were classified as pathogenic mutations based on previous publications, with p.M918T being the most frequent (4 cases), followed by p.C634R (3 cases) and p.C618R (3 cases). Mutations were significantly associated with specific histological patterns, such as the nested/insular pattern (p=.026), giant cells (p=.007), nuclear pleomorphism (p=.018), stippled chromatin (p=.044), and amyloid deposits (p=.024). No mutations were found in germline analyses, suggesting these were somatic alterations.

CONCLUSIONS

Our results provided the first comprehensive analysis of RET mutations in Vietnamese MTC patients. The most frequent mutation was p.M918T, followed by p.C634R and p.C618R. Mutations in these three exons were linked to specific histopathological features. Information on mutational profiles of patients with MTC will further aid in the development of targeted therapeutics to ensure effective disease management.