Thyroid nodules are common, and the accurate diagnosis of cancer or benign disease is important for the effective clinical management of patients. Molecular markers are a helpful diagnostic tool, particularly for cytologically indeterminate thyroid nodules. In the past few years, significant progress has been made in developing molecular markers for clinical use in fine-needle aspiration specimens, including gene mutation panels and gene expression classifiers. With the availability of next generation sequencing technology, gene mutation panels can be expanded to interrogate multiple genes simultaneously and to provide yet more accurate diagnostic information. In addition, recently several new molecular markers of thyroid cancer have been identified that offer diagnostic, prognostic, and therapeutic information that might be of value in guiding individualized management of patients with thyroid nodules.
Susan J Hsiao and Yuri E Nikiforov
Viktoria Evdokimova, Manoj Gandhi, Jayanagendra Rayapureddi, James R Stringer, and Yuri E Nikiforov
Ionizing radiation (IR) exposure increases the risk of thyroid cancer and other cancer types. Chromosomal rearrangements, such as RET/PTC, are characteristic features of radiation-associated thyroid cancer and can be induced by radiation in vitro. IR causes double-strand breaks (DSBs), suggesting that such damage leads to RET/PTC, but the rearrangement mechanism has not been established. To study the mechanism, we explored the possibility of inducing RET/PTC by electroporation of restriction endonucleases (REs) into HTori-3 human thyroid cells. We used five REs, which induced DSB in a dose-dependent manner similar to that seen with IR. Although all but one RE caused DSB in one or more of the three genes involved in RET/PTC, rearrangement was detected only in cells electroporated with either PvuII (25 and 100 U) or StuI (100 and 250 U). The predominant rearrangement type was RET/PTC3, which is characteristic of human thyroid cancer arising early after Chernobyl-related radioactive iodine exposure. Both enzymes that produced RET/PTC had restriction sites only in one of the two fusion partner genes. Moreover, the two enzymes that produced RET/PTC had restriction sites present in clusters, which was not the case for RE that failed to induce RET/PTC. In summary, we establish a model of DSB induction by RE and report for the first time the formation of carcinogenic chromosomal rearrangements, predominantly RET/PTC3, as a result of DSB produced by RE. Our data also raise a possibility that RET/PTC rearrangement can be initiated by a complex DSB that is induced in one of the fusion partner genes.
Raffaele Ciampi, Thomas J Giordano, Kathryn Wikenheiser-Brokamp, Ronald J Koenig, and Yuri E Nikiforov
Chromosomal rearrangements of the RET proto-oncogene (RET/PTC) are the common feature of papillary thyroid carcinoma (PTC). In this study, we report the identification, cloning, and functional characterization of a novel type of RET/PTC rearrangement that results from the fusion of the 3′-portion of RET coding for the tyrosine kinase (TK) domain of the receptor to the 5′-portion of the Homo sapiens hook homolog 3 (HOOK3) gene. The novel fusion was identified in a case of PTC that revealed a gene expression signature characteristic of RET/PTC on DNA microarray analysis, but was negative for the most common types of RET rearrangement. A fusion product between exon 11 of HOOK3 and exon 12 of RET gene was identified by 5′RACE, and the presence of chimeric HOOK3-RET protein of 88 kDa was detected by western blot analysis with an anti-RET antibody. The protein is predicted to contain a portion of the coiled-coil domains of HOOK3 and the intact TK domain of RET. Expression of the HOOK3-RET cDNA in NIH3T3 cells resulted in the formation of transformed foci and in tumor formation after injection into nude mice, confirming the oncogenic nature of HOOK3-RET.
Arivarasan Karunamurthy, Federica Panebianco, Susan J Hsiao, Jennie Vorhauer, Marina N Nikiforova, Simion Chiosea, and Yuri E Nikiforov
The EIF1AX gene mutations have been recently found in papillary thyroid carcinoma (PTC) and anaplastic thyroid carcinoma (ATC). The prevalence of these mutations in other types of thyroid cancers and benign nodules is unknown. In this study, we analyzed the occurrence of EIF1AX mutations in exons 2, 5, and 6 of the gene in a series of 266 thyroid tumors and hyperplastic nodules by either Sanger or next-generation sequencing (ThyroSeq v.2). In addition, 647 thyroid fine-needle aspiration (FNA) samples with indeterminate cytology were analyzed. Using surgically removed samples, EIF1AX mutations were detected in 3/86 (2.3%) PTC, 1/4 (25%) ATC, 0/53 follicular carcinomas, 0/12 medullary carcinomas, 2/27 (7.4%) follicular adenomas, and 1/80 (1.3%) hyperplastic nodules. Among five mutation-positive FNA samples with surgical follow-up, one nodule was PTC and others were benign follicular adenomas or hyperplastic nodules. Overall, among 33 mutations identified, A113_splice mutation at the intron 5/exon 6 splice site of EIF1AX was the most common. All four carcinomas harbored A113_splice mutation and three of them had one or more coexisting mutations, typically RAS. All PTC carrying EIF1AX mutations were encapsulated follicular variants. In summary, this study shows that EIF1AX mutations occur not only in thyroid carcinomas, but also in benign nodules. The most common mutation hotspot is the A113_splice, followed by a cluster of mutations in exon 2. When found in thyroid FNA samples, EIF1AX mutations confer ~20% risk of cancer; the risk is likely to be higher in nodules carrying a A113_splice mutation and when EIF1AX coexists with RAS mutations.
William Reed Doerfler, Alyaksandr V. Nikitski, Elena M. Morariu, N. Paul Ohori, Simion I Chiosea, Michael S. Landau, Marina Nikiforova, Yuri E Nikiforov, Linwah Yip, and Pooja Manroa
Hürthle cell carcinoma (HCC) is a distinct type of thyroid cancer genetically characterized by DNA copy number alterations (CNA), typically of genome haploidization type (GH-type). However, whether CNA also occur in benign Hürthle cell adenomas (HCA) or Hürthle cell hyperplastic nodules (HCHN), and have diagnostic impact in fine needle aspiration (FNA) samples, remains unknown. To address these questions, we (i) analyzed 26 HCC, 24 HCA, and 8 HCHN tissues for CNA and other mutations using ThyroSeq v3 (TSv3) next-generation sequencing panel, and (ii) determined cancer rate in 111 FNA samples with CNA and known surgical outcome. We identified CNA, more often of the GH-type, in 81% of HCC and in 38% HCA, but not in HCHN. Among 4 HCC with distant metastasis, all had CNA and 3 TERT mutations. Overall, positive TSv3 results were obtained in 24 (92%) HCC, including all with ATA high risk of recurrence or metastasis. Among 111 FNA cases with CNA, 38 (34%) were malignant, and 73 (66%) benign. A significant correlation between cancer rate and nodule size was observed, particularly among cases with GH-type CNA, where every additional centimeter of nodule size increased the malignancy odds by 1.9 (95% CI 1.3-2.7; P=0.001). In summary, the results of this study demonstrate that CNA characteristic of HCC also occur in HCA, although with lower frequency, and probability of cancer in nodules with CNA increases with nodule size. Detection of CNA, in conjunction with other mutations and nodule size, is helpful in predicting malignancy in thyroid nodules.
Federica Panebianco, Alyaksandr V Nikitski, Marina N Nikiforova, Cihan Kaya, Linwah Yip, Vincenzo Condello, Abigail I Wald, Yuri E Nikiforov, and Simion I Chiosea
ALK fusions are found in various tumors, including thyroid cancer, and serve as a diagnostic marker and therapeutic target. Spectrum and outcomes of ALK fusions found in thyroid nodules and cancer are not fully characterized. We report a series of 44 ALK-translocated thyroid neoplasms, including 31 identified preoperatively in thyroid fine-needle aspirates (FNA). The average patients’ age was 43 years (range, 8–76 years); only one with radiation history. All 19 resected thyroid nodules with ALK fusion identified preoperatively were malignant. Among nodules with known surgical pathology (n = 32), 84% were papillary thyroid carcinomas (PTCs) and 16% poorly differentiated thyroid carcinomas (PDTCs). PTCs showed infiltrative growth with follicular architecture seen exclusively (30%) or in combination with papillary and/or solid growth (37%). Tumor multifocality was seen in 10 (31%) PTC cases. Most PDTC had a well-differentiated PTC component. Lymph node metastases were identified in 10/18 (56%) patients with neck dissection. The most common ALK fusion partners were STRN (n = 22) and EML4 (n = 17). In five cases, novel ALK fusion partners were discovered. All five PDTCs carried STRN-ALK fusion. On follow-up, ten patients were free of disease at 2–108 months, whereas two patients with PDTC died of disease. In summary, ALK fusion-positive thyroid carcinomas are typically infiltrative PTC with common follicular growth, which may show tumor dedifferentiation associated with increased mortality. Compared to EML4-ALK, STRN-ALK may be more common in PDTC, and ~10% of ALK fusions occur to rare gene partners. When ALK fusion is detected preoperatively in FNA samples, malignancy should be expected.