MicroRNA Signature in Thyroid Fine Needle Aspiration Cytology Applied to “Atypia of Undetermined Significance” Cases

Abstract

Background: MicroRNA (miR) expression signatures are proposed to be able to differentiate thyroid cancer from benign thyroid lesions. We selected eight miRs (miR-146b, -221, -187, -197, -346, -30d, -138, and -302c) to examine the potential use of miRs to supplement diagnostic cytology in cases designated as ''atypia of undetermined significance.'' Methods: miR expression was measured in thyroid fine needle aspiration (FNA) specimens by quantitative polymerase chain reaction. Gene expression analyses and linear discriminant analysis (LDA) were performed in a training sample set (n = 60) to obtain a classification rule to predict FNA cases as benign or malignant. The predictions were cross-validated by comparing with the corresponding histological diagnoses. A validation sample set (n = 68) was further tested with the established four-miR LDA classification rule. Results: A set of four miRs (miR-146b, -221, -187, and -30d) was identified that could differentiate malignant from benign lesions. A four-miR LDA classification rule was obtained and used to predict FNA cases as benign or malignant. For the training sample set, we obtained a diagnostic accuracy of 93.3%, sensitivity of 93.2%, specificity of 93.8%, positive predictive value (PPV) of 0.98, and negative predictive value (NPV) of 0.83. For the validation sample set, we obtained a diagnostic accuracy of 85.3%, sensitivity of 88.9%, specificity of 78.3%, PPV of 0.89, and NPV of 0.78. For the 30 atypia cases in the validation sample set, we obtained a diagnostic accuracy of 73.3%, sensitivity of 63.6%, specificity of 78.9%, PPV of 0.64, and NPV of 0.79. Based on the miR predictions, we classified the atypia cases predicted as ''malignant'' into ''high risk'' and those predicted as ''benign'' into ''low risk'' categories. While thyroid carcinomas, particularly papillary thyroid carcinomas (PTCs), were relatively enriched in the high-risk category, this particular miR panel is subject to inaccurate results in follicular neoplasias in atypia cases. Conclusions: We demonstrate that miR amplification from FNA samples is feasible and that the particular four miR profile in this study can identify PTCs. However, further refinement is required for application to FNA cytology of ''atypia of undetermined significance'' cases due to low accuracy in classifying follicular neoplasias.

MicroRNA expression profile helps to distinguish benign nodules from papillary thyroid carcinomas starting from cells of fine-needle aspiration

“…Recently, there has been increasing interest in examining the expression profile of miRNAs in thyroid cancer to understand tumorigenesis and to improve thyroid cancer diagnosis (16,17,18,19,20,21,22,23,24,25,26). He et al (16) detected preliminary evidence of a potential role for miRNA in PTC.…”

“…The identification and validation of a predictive molecular biomarker panel would be very helpful in distinguishing benign from malignant nodules in patients with undetermined FNA cytology. Several recent studies used miRNA microarrays to demonstrate a characteristic molecular expression pattern to differentiate benign from malignant thyroid nodules (16,17,18,19,20,21,22,23,24,25,26), and RT-PCR TaqMan miRNA assay identifies a limited number of miRNAs that are significantly upregulated in malignant thyroid nodules with respect to normal thyroid tissue, hyperplastic thyroid nodules, and multinodular goiter (16,17,20), suggesting miRNA analysis as a promising tool in diagnostic thyroid pathology.…”

Thyroid nodules and differentiated thyroid cancer: update on the Brazilian consensus

“…Unfortunately, a panel with these four markers (BRAF, RAS, and rearrangements RET/PTC and PAX8/PPARy) fails to identify 36% of malignant cases (sensitivity of 64%) in clinical practice (49). Other markers, such as microRNAs, are being investigated (50). Recently, a novel test designed to rule out malignancy exhibited a high negative predictive value (95%) in nodules with undetermined cytology (51).…”

Value of Molecular Tests in Cytologically Indeterminate Lesions of Thyroid

“…As a small molecule, it is relatively stable in FNA specimens and in formalin-fixed, paraffin-embedded cell-block materials and is, therefore, amenable to detection. Specific microRNA profiles (panels) have been identified in a variety of tumors, and their diagnostic utility has also been explored in thyroid neoplasms, including FNA indeterminate lesions [37][38][39][40][41] (Table). The panels are usually small, consisting of 2 to 4 microRNAs, and their sensitivity, specificity, and accuracy are improving as different studies on microRNAs become available.…”