Endocrine Abstracts

Background: MicroRNAs (miRNAs) are small non-protein encoding RNAs which negatively regulate gene expression. Tissue miRNA profiles may be useful to distinguish benign from malignant lesions. Recently, we have identified in the serum of a retrospective series of patients, with benign nodular goiter (n=80) and papillary thyroid cancer (PTC: n=79), two miRNAs (-190 and -95) that in combination (providing the risk of malignancy defined as pmiRNA) allow the differential diagnosis of thyroid nodules with great accuracy. This study was aimed to confirm the diagnostic accuracy of miRNA-190 and -95 in a prospective series of patients.

Methods: Blood samples were collected from 126 consecutive patients undergoing fine-needle aspiration cytology at our Institute. miRNAs were extracted from serum using the miRNeasy Serum/Plasma Kit (Qiagen), and reverse-transcribed using Megaplex Human microRNA RT primers pools v2.1 (Life Technologies). cDNA was then pre-amplified. Relative expression quantification was evaluated by the comparative cycle threshold (CT) method (2^−ΔΔCt) (Rotor-gene Q, Qiagen). Endogenous miRNA-16 and miRNA-451 were selected as reference to normalize miRNA expression values.

Results: Based on cytology (following BTA guideline): the lesions were benign (Thy2) in 85/121 (70.2%) cases, suspicious for malignancy or malignant (Thy4/5) in 14/121 (11.6%), indeterminate (Thy3) in 16/121 (13.2%), and non diagnostic (Thy1) in 6/121 (5%). A subgroup of 48 patients underwent surgery and the lesions at histology were benign in 30/48 (62.5%) cases and malignant in 18/48 (37.5%). PmiRNA showed a high sensitivity (84%), specificity (93.5%), and diagnostic accuracy (90%) in PTC diagnosis. Moreover, by applying pmiRNA, we could have avoided two out of three unnecessary surgeries in patients with Thy3 cytology.

Conclusions: These preliminary data confirm that pmiRNA may be useful as a non-invasive diagnostic tool for the differential diagnosis of thyroid nodules, particularly in case of indeterminate lesions where pmiRNA role is promising but further studies are warranted.

Disclosure: PRIN No. 2010RNY8T_001; MOH-GR-2010-2321454.