The quest for diagnostic molecular markers for thyroid nodules with indeterminate or suspicious cytology

Application of Immunocytochemistry on Cell Block Sections for the Investigation of Thyroid Lesions

OBJECTIVE

To investigate the potential of Classification and Regression Trees (CARTs) for the diagnosis of thyroid lesions based on cell block immunocytochemistry and cytological outcome.

STUDY DESIGN

A total of 956 histologically confirmed cases (673 benign and 283 malignant) from patients with thyroid nodules were prepared via liquid-based cytology and evaluated; 4 additional slides were stained for cytokeratin 19 (CK-19), galectin 3 (Gal-3), Hector Battifora mesothelial cell 1 (HBME-1), and thyroglobulin. On the basis of immunocytochemistry and the cytological diagnosis, a CART algorithm was constructed and used for evaluation.

RESULTS

The major important factors contributing to the diagnostic CART model were: cytological outcome, CK-19, Gal-3, and HBME-1. The sensitivity and specificity of the cytological diagnosis were 96.27% and 88.26%, respectively (cut-off: category 3 of The Bethesda System [TBS-3]). The introduction of immunocytochemistry and the CART model increased the sensitivity and specificity to 98.88% and 99.11%, respectively. CK-19 presented the best performance for discriminating papillary thyroid carcinomas, followed by HBME-1 and Gal-3. In the TBS-2 cases, CK-19 and, subsequently, Gal-3 were important immunocytochemistry markers. Ultimately, CK-19 and HBME-1 on TBS-5 or TBS-6 cases demonstrated the best results.

CONCLUSIONS

The hierarchical structure of the CART model provides a diagnostic algorithm linked with the risk of malignancy at every step of the procedure. It also provides guidance on the use of ancillary examinations as it goes by simple, human understandable rules.

Serum and urine 1H NMR-based metabolomics in the diagnosis of selected thyroid diseases

Early detection of nodular thyroid diseases including thyroid cancer is still primarily based on invasive procedures such as fine-needle aspiration biopsy. Therefore, there is a strong need for development of new diagnostic methods that could provide clinically useful information regarding thyroid nodular lesions in a non-invasive way. In this study we investigated ¹H NMR based metabolic profiles of paired urine and blood serum samples, that were obtained from healthy individuals and patients with nodular thyroid diseases. Estimation of predictive potential of metabolites was evaluated using chemometric methods and revealed that both urine and serum carry information sufficient to distinguish between patients with nodular lesions and healthy individuals. Data fusion allowed to further improve prediction quality of the models. However, stratification of tumor types and their differentiation in relation to each other was not possible.

Value of Molecular Tests in Cytologically Indeterminate Lesions of Thyroid

CONTEXT

Fine-needle aspiration has been the initial step in the workup of thyroid nodular lesions and has successfully reduced the number of unnecessary surgeries and improved preoperative malignancy detection. However, up to one-third of cases fall in the diagnostically "indeterminate group," which poses a patient-management challenge. objective: To review the characteristics of molecular tests useful for stratifying the malignancy risk of indeterminate thyroid lesions, including their advantages and limitations.

DATA SOURCES

PubMed.

CONCLUSIONS

Molecular tests are useful for triage of indeterminate thyroid nodules initially diagnosed by using fine-needle aspiration. Immunocytochemistry is readily available with the shortest turnaround time among the molecular tests but suffers from poor reproducibility and low interpretation concordance. Gene mutation analysis is superior in detecting malignancies as a rule-in test, despite low specificity. Next-generation sequencing seems promising but needs more validations before widespread use. Gene expression profiling is more suitable for detecting benign lesions as a rule-out test to avoid unnecessary surgeries but is not reliable in excluding malignancies. MicroRNA profiling has great potential for both risk stratification and predicting prognosis but is limited by significant variations in sensitivity and specificity. Although many questions still need to be answered, taken together, molecular tests are a promising option for classifying cytologically indeterminate thyroid nodular lesions.

Value of distinguishing differentiated thyroid carcinoma by miRNA

Current methods for diagnosing thyroid carcinoma are time consuming or expensive. Thus, alternative approaches are required. In the present study, microRNAs (miRNAs) with higher sensitivity and specificity were screened while distinguishing between differentiated thyroid carcinoma (DTC) and subtype papillary thyroid carcinoma (PTC). A total of 120 cases suspected of having thyroid carcinoma were selected and examined using clinical color Doppler ultrasound, and computed tomography scan at the same time. The tissue specimens were obtained with fine needle aspiration, multiphase biopsy and surgical resection. The expression of miR146b, miR221 and miR222 was detected uisng the RT-quantitative polymerase chain reaction method. The receiver operating characteristic curve was used to obtain the cut-off value. Pathological examination identified 8 cases of normal thyroid tissue; 9 cases of hyperplastic nodules; 12 cases of thyroid adenoma; and 91 cases of thyroid carcinoma, of which 59 cases were DTC, 15 cases were follicular carcinoma and 17 cases were undifferentiated carcinoma. In the thyroid carcinoma, the expression levels of miR146b, miR221 and miR222 were significantly higher than those of other tissues (P<0.05). The expression levels of these miRNAs in the differentiated type were also significantly higher than those in the undifferentiated type (P<0.05). A comparison of the differentiated subunit identified no statistically significant difference (P>0.05). Following diagnosis of DTC, the area under curve (AUC) of miR146b, miR221 and miR222 was 0.832, 0.806 and 0.745, respectively; the cut-off values were 1.346, 1.213 and 1.425, respectively; susceptibility was 72.8, 71.5 and 68.7%, respectively; and specificity was 62.3, 60.9 and 59.3%, respectively. The AUC of the combined miR-146b and -221 following diagnosis of PTC was 0.695; the cut-off values were 1.506 and 1.462, respectively; susceptibility was 78.9%; and specificity was 68.5%. The AUC of the combined miR-146b and -222 was 0.677; the cut-off values were 1.523 and 1.443, respectively; susceptibility was 76.3%; and specificity was 66.4%. The AUC of the combined miR-221 and -222 was 0.662; the cut-off values were 1.564 and 1.437, respectively; susceptibility was 74.9%; and specificity was 68.2%. In conclusion, miR146b, miR221 and miR222 may be used as susceptibility and specificity indices of DTC, although they cannot be used as susceptibility or specificity indices for distinguishing PTC. Combining the two indices together can improve diagnostic accuracy to a certain extent.

The utility of molecular markers in pre-operative assessment of thyroid nodules

The pre-operative diagnosis of thyroid tumors is determined by gold standard fine needle aspiration (FNA) biopsy. This has been widely accepted and offers the most cost-effective approach for evaluation of thyroid nodules. However, its diagnostic accuracy can pose a challenging scenario to surgeons. These diagnostic difficulties may subject patients to unnecessary thyroidectomies for benign thyroid nodules. Thus, additional molecular tests are needed to improve the sensitivity and specificity of FNA. The role of molecular markers is being proposed to predict the type and risk of malignancy to abate the need for diagnostic thyroidectomies. This review discusses their utility and validity in pre-operative diagnosis of thyroid nodules and how these markers can enhance the accuracy of FNA cytology.

Role of molecular diagnostic markers in the management of indeterminate and suspicious thyroid nodules

Incidental thyroid nodules are commonly found during routine neck examination. Fine needle aspiration (FNA) followed by cytological examination is currently considered as the most reliable method for evaluation of thyroid nodules. However, 10–40% of FNA results are inconclusive, and are reported as indeterminate or suspicious. Approximately 20% of indeterminate or suspicious nodules are malignant. Therefore, there has been an increasing trend in use of molecular markers as an adjunctive measure for more accurate preoperative diagnosis of indeterminate or suspicious nodules. Molecular markers can be used alone or as a part of molecular panels. Although some investigations revealed promising findings regarding the potential use of molecular markers in the management of thyroid nodules, their true impact on management of patients with indeterminate nodules is still unclear.

Follicular adenomas exhibit a unique metabolic profile. ¹H NMR studies of thyroid lesions

Thyroid cancer is the most common endocrine malignancy. However, more than 90% of thyroid nodules are benign. It remains unclear whether thyroid carcinoma arises from preexisting benign nodules. Metabolomics can provide valuable and comprehensive information about low molecular weight compounds present in living systems and further our understanding of the biology regulating pathological processes. Herein, we applied ¹H NMR-based metabolic profiling to identify the metabolites present in aqueous tissue extracts of healthy thyroid tissue (H), non-neoplastic nodules (NN), follicular adenomas (FA) and malignant thyroid cancer (TC) as an alternative way of investigating cancer lesions. Multivariate statistical methods provided clear discrimination not only between healthy thyroid tissue and pathological thyroid tissue but also between different types of thyroid lesions. Potential biomarkers common to all thyroid lesions were identified, namely, alanine, methionine, acetone, glutamate, glycine, lactate, tyrosine, phenylalanine and hypoxanthine. Metabolic changes in thyroid cancer were mainly related to osmotic regulators (taurine and scyllo- and myo-inositol), citrate, and amino acids supplying the TCA cycle. Thyroid follicular adenomas were found to display metabolic features of benign non-neoplastic nodules and simultaneously displayed a partial metabolic profile associated with malignancy. This finding allows the discrimination of follicular adenomas from benign non-neoplastic nodules and thyroid cancer with similar accuracy. Moreover, the presented data indicate that follicular adenoma could be an individual stage of thyroid cancer development.

Whole-transcriptome profiling of thyroid nodules identifies expression-based signatures for accurate thyroid cancer diagnosis

PURPOSE

Due to the limitations of fine-needle aspiration biopsy (FNAB) cytopathology, many individuals who present with thyroid nodules eventually undergo thyroid surgery to diagnose thyroid cancer. The objective of this study was to use whole-transcriptome profiling to develop and validate a genomic classifier that significantly improves the accuracy of preoperative thyroid cancer diagnosis.

MATERIALS AND METHODS

Nucleic acids were extracted and amplified for microarray expression analysis on the Affymetrix Human Exon 1.0 ST GeneChips from 1-mm-diameter formalin-fixed and paraffin-embedded thyroid tumor tissue cores. A training group of 60 thyroidectomy specimens (30 cancers and 30 benign lesions) were used to assess differential expression and for subsequent generation of a genomic classifier. The classifier was validated in a blinded fashion on a group of 31 formalin-fixed and paraffin-embedded thyroid FNAB specimens.

RESULTS

Expression profiles of the 57 thyroidectomy training and 31 FNAB validation specimens that passed a series of quality control steps were analyzed. A genomic classifier composed of 249 markers that corresponded to 154 genes, had an overall validated accuracy of 90.0% in the 31 patient FNAB specimens and had positive and negative predictive values of 100% and 85.7%, respectively. The majority of the identified markers that made up the classifier represented non-protein-encoding RNAs.

CONCLUSIONS

Whole-transcriptome profiling of thyroid nodule surgical specimens allowed for the development of a genomic classifier that improved the accuracy of preoperative thyroid cancer FNAB diagnosis.

Molecular markers in thyroid cytology: diagnostic and prognostic implications

The discovery of thyroid nodules in the general population has risen markedly with the greater use of ultrasound resulting in increasing use of ultrasound-guided fine needle aspiration (FNA) biopsy. Although FNA can identify the majority of nodules as either benign or malignant, one-third of aspirates demonstrate indeterminate cytologic characteristics. Though most of these nodules will be pathologically benign, thyroid surgery has usually been needed to make an accurate diagnosis, and the extent of surgery needed (lobectomy versus total thyroidectomy) is difficult to predict in advance. New molecular techniques are being investigated and used clinically to improve decision making in patients with thyroid nodules with indeterminate cytology. These molecular markers have the potential to help clinicians decide which patients may be monitored without thyroid surgery, and also the optimal strategy when surgery is felt to be necessary.

Progress in molecular-based management of differentiated thyroid cancer

Substantial developments have occurred in the past 5-10 years in clinical translational research of thyroid cancer. Diagnostic molecular markers, such as RET-PTC, RAS, and BRAF(V600E) mutations; galectin 3; and a new gene expression classifier, are outstanding examples that have improved diagnosis of thyroid nodules. BRAF mutation is a prognostic genetic marker that has improved risk stratification and hence tailored management of patients with thyroid cancer, including those with conventionally low risks. Novel molecular-targeted treatments hold great promise for radioiodine-refractory and surgically inoperable thyroid cancers as shown in clinical trials; such treatments are likely to become a component of the standard treatment regimen for patients with thyroid cancer in the near future. These novel molecular-based management strategies for thyroid nodules and thyroid cancer are the most exciting developments in this unprecedented era of molecular thyroid-cancer medicine.

Promise and pitfalls of molecular markers of thyroid nodules

Thyroid nodules are common in the general population with a prevalence of 5-7% The initial evaluation of thyroid nodules commonly involves thyroid function tests, an ultrasound (USG) and fine needle aspiration biopsy (FNAB). The optimal management of patients with thyroid nodules with indeterminate cytology is plagued by the lack of highly sensitive and specific diagnostic modalities In this article we attempt to review the available literature on the molecular markers which are increasingly being studied for their diagnostic utility in assessing thyroid nodules. The various molecular markers consist of gene mutations, gene re arrangements, RNA based assays and immunohistochemical markers. The molecular markers definitely would help to optimise the management of such patients.