[The possibility of using freely circulating DNA blood plasma in preoperative diagnosis of thyroid tumors].

BACKGROUND: The feasibility of using molecular genetic markers for the diagnosis of thyroid tumors and the impact on the prognosis of thyroid cancer are being actively investigated. The most interesting are genes, the detection of which is associated not only with thyroid cancer, but also with a more aggressive course of the disease. The ability to diagnose the molecular profile of minimally invasive methods with the study of freely circulating DNA tumor tissue in blood plasma is a modern trend of medicine. AIMS: to evaluate the frequency of somatic mutations in the «hot spots» of BRAF, KRAS, KRAS, EIF1AX and TERT genes in circulating DNA of blood plasma. MATERIALS AND METHODS: Samples of DNA, extracted from the removed tumor and non-tumor thyroid tissue, were tested for the presence of somatic mutations in hot spots of the genes BRAF, KRAS, NRAS, TERT, and EIF1AX and then in identifying mutations and testing appropriate samples of free circulating DNA in blood plasma. RESULTS: mutations in the» hot spots «of the BRAF gene (exon 15, codon area 600-601) were found in 54 patients, mutations in the» hot spots « of the NRAS gene (exon 3, codon 61) – in 12 patients; mutations in the hot spots of the KRAS, TERT and EIF1AX genes were not detected. In freely circulating blood plasma DNA, BRAF gene mutations were detected in 1 case, NRAS gene mutations were detected in 1 case. CONCLUSIONS: the use of freely circulating DNA of blood plasma in the testing of the studied sample did not show the feasibility for the diagnosis of thyroid tumors.

Radiation exposure does not significantly contribute to the risk of recurrence of Chernobyl thyroid cancer.

CONTEXT: Papillary thyroid carcinoma (PTC) in patients exposed to environmental radioiodine after the Chernobyl accident is thought to have a relatively aggressive clinical course. Long-term results of treatment are not well known, especially in comparison with sporadic PTC. OBJECTIVE: The determination of risk factors for PTC recurrence in a controlled for baseline factors group of patients with radiation-related and sporadic PTC. DESIGN: Retrospective cohort study involving patients treated for PTC and followed-up in 1991-2008. Risk factors were assessed by stratified analysis using the proportional hazard model. SETTING: Referral center-based. PATIENTS: A total of 497 patients were enrolled. Patients exposed to radioiodine were 172 individuals with reconstructed individual radiation thyroid doses ranging 51-3170 mGy. Patients with sporadic PTC included 325 individuals matched to exposed patients for sex, age ± 5 yr and time to treatment ± 2 yr. MAIN OUTCOME MEASURE: Cancer recurrence. RESULTS: Nodal disease increased the recurrence rate (HR = 5.21; 95% CI = 1.63-16.7) while the presence of tumor capsule (HR = 0.17; 95% CI = 0.06-0.45) and, particularly, treatment according to the Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer significantly reduced it (HR = 0.16; 95% CI = 0.06-0.42). None of the tested variables interacted with radiation factor. CONCLUSIONS: PTC developing after internal exposure to radioiodine does not display specific risk factors for recurrence different from those in sporadic PTC. Common treatment approaches for patients with PTC should be recommended regardless of a history of radiation exposure.

TP53 codon 72 polymorphism in radiation-associated human papillary thyroid cancer.

The study investigated an association between the germline polymorphism at TP53 codon 72 and the development of papillary thyroid cancer (PTC) following exposure to radiation from the Chernobyl accident. TP53 genotype was examined in 48 pediatric/adolescent (age at diagnosis <18 years) and 68 adult post-Chernobyl patient with PTC, 53 adult patients with sporadic PTC and 313 healthy individuals from Russian-Ukrainian population. In addition, we evaluated loss of heterozygosity for TP53 and the allele expression ratio. The genotype of the patients was correlated with clinicopathological data. Arg TP53 homozygotes were found to be significantly underrepresented among adults with post-Chernobyl PTC, but not in children and adolescents when compared with sporadic PTC cases and the general population. In the tumors, cell transformation did not lead to allelic loss or biased TP53 allele expression in heterozygous individuals. None of TP53 genotypes specifically associated with tumor stage and morphology, however there were particular correlations with lymph node status in certain age groups of radiation-associated cases not seen in sporadic PTCs. The findings suggest TP53 allele combinations other than Arg/Arg may contribute to the risk of development of PTC in individuals exposed to radiation during their late childhood, adolescence or in young adulthood.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) of the thyroid with neck lymph node metastasis: a case report.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is an extremely rare type of thyroid tumor. It has been reported only 20 times in the English literature. This tumor occurs predominantly in young patients and has a protracted clinical course despite the occurrence of metastases. In the recent literature SETTLE has been considered to be a tumor of low malignant potential with distant metastases developing some years after diagnosis. Herein we report a case of SETTLE in a 22-yr-old man in which a lymph node metastasis developed soon after the primary tumor manifestation. Histological examination of the tumor showed the predominantly monophasic variant of SETTLE. The primary and metastatic lesions were highly cellular tumors composed of sheets of spindle cells that were positive for pan-cytokeratin and vimentin and negative for thyroglobulin, calcitonin, and S-100 protein.

The BRAFT1796A transversion is a prevalent mutational event in human thyroid microcarcinoma.

Mutation in exon 15 of the BRAF gene is a characteristic feature of human thyroid papillary carcinoma (PTC). To determine the role of such mutation(s) in the neoplastic progression of thyroid papillary microcarcinoma (PMC), we analyzed 46 cases from 31 Russian and 15 Japanese patients with PMC. Mutated BRAF (the BRAFT1796A transversion in all cases) was detected in 13/46 (28.2%) of the tumors: 9/31 (29.0%) and 4/15 (26.6%) in Russian and Japanese individuals, respectively, displaying no signs of difference in the mutational rates in the PMCs from patients with diverse genetic background seen in PTCs. Occurrence of the BRAF mutation did not significantly correlate with the patients' gender, age at presentation, metastatic indices or with papillary, mixed papillary and follicular, and solid/trabecular PMC histotype. On the contrary, the tumors of follicular morphology significantly associated with the mutation-free genotype (P=0.018), and in the mixed-type tumors characterized by co-occurrence of well-differentiated and less differentiated components, the BRAF mutational frequency was significantly elevated (P=0.020). The results indicate the BRAFT1796A mutation is prevalent in PMCs, and thus these tumors may have a spectrum of genetic events partly overlapping with that of PTCs.

Novel tumorigenic rearrangement, Delta rfp/ret, in a papillary thyroid carcinoma from externally irradiated patient.

Molecular analysis of cDNA derived from a papillary thyroid carcinoma (PTC) (follicular variant of papillary thyroid carcinoma on histology) which developed in an externally irradiated patient 4 years after exposure identified a portion of the 5' region, exons 1-3, of the rfp gene juxtaposed upstream of the fragment encoding the tyrosine kinase (TK) domain of the ret gene. The fusion gene, termed Delta rfp/ret, was the result of a balanced chromosomal translocation t(6;10) (p21.3;q11.2) confirmed by interphase FISH painting, with breakpoints occurring in introns 3 and 11 of the rfp and ret genes, respectively. Both Delta rfp/ret and reciprocal ret/rfp chimeric introns had small deletions around breakpoints consistent with presumed misrepair of a radiation-induced double-strand DNA break underlying the rearrangement. No extensive sequence homology was found between the fragments flanking the breakpoints. The fusion protein retained the propensity to form oligomers likely to be mediated by a coiled-coil of the RFP polypeptide as assessed by a yeast two-hybrid system. NIH 3T3 fibroblasts stably transfected with a mammalian expression vector encoding full-length Delta RFP/RET readily gave rise to the tumors in athymic mice suggestive of high transforming potential of the fusion protein. Thus, the Delta rfp/ret rearrangement may be involved in a causative manner in cancerogenesis and provides additional evidence of the role of activated ret oncogene in the development of a subset of papillary thyroid carcinoma.

Large deletions in mitochondrial DNA in radiation-associated human thyroid tumors.

Paired DNA samples of tumor and normal thyroid tissue from adult patients possibly exposed to radioactive Chernobyl fallout [11 cases of papillary thyroid carcinoma (PTC) and 6 follicular adenomas] and from control samples (9 PTC occurring in Japanese patients) were examined for the relative mitochondrial DNA (mtDNA) content, prevalence and level of common deletion (CD), and large-scale deletions in mtDNA. Elevated relative mtDNA content as estimated by real-time PCR was found in tumor tissue in most cases, but no significant correlation with the level of radioiodine contamination of patients' residency nor with clinicopathological data were found. CD was detected in every DNA specimen from all types of tissue regardless of the presence of oxyphillic cell changes. Elevated level of the CD was predominantly found in tumor tissue of the radiation-associated group but not in sporadic PTC. No correlation was noted with clinicopathological parameters, radioiodine contamination, and relative mtDNA content. The quantity of large-scale deletions in mtDNA was elevated in most tumor tissues, especially in the radiation-associated group and tended to correlate with the level of radiopollutant in PTC. In contrast to sporadic PTC, highly significant-positive correlation between the presence of large scale mtDNA deletions and relative mtDNA content was found in radiation-associated tumors (P = 0.001 and P = 0.019 in PTC and follicular adenoma, respectively). Normal tissue displayed the inverse tendency. No association with level of the CD was found in either group of cases. Concordant increase of both relative mtDNA content and number of mtDNA deletions was detected more often in radiation-associated PTC than in sporadic PTC. Thus, simultaneous determination of the number of large-scale mtDNA deletions and relative mtDNA content may be useful to elucidate molecular distinctive features of radiation-associated thyroid tumors.