Molecular detection of circulating thyroid specific transcripts (TSHR/Tg-mRNAs) in thyroid cancer patients: Their diagnostic significance

Abstract

Thyroid cancer is the most prevalent endocrine malignancy. The preoperative diagnosis of differentiated thyroid cancer (DTC) that relies solely on fine-needle aspiration (FNAC) biopsy, sometimes possesses conflicting results. New molecular markers for thyroid cancer have been investigated with most of them based on the detection in thyroid nodules or tumor tissue specimens. Recently, it was possible to detect thyroid cancer cells in the circulation by measuring the mRNA of thyroid specific genes. Among these, thyroglobulin and more recently thyroid stimulating hormone receptor mRNAs, TSHR/Tg-mRNAs in peripheral blood might serve as cancer-specific markers. These have become promising new circulating markers for thyroid cancer. The purpose of this study is to assess TSHR/Tg-mRNAs as diagnostic molecular markers for thyroid cancer and if they can be used preoperatively in synergy with FNAC. This study was performed on 60 subjects; 20 healthy volunteers and 40 patients; including 16 patients with benign thyroid diseases, 24 patients with thyroid cancer; 18 patients with newly diagnosed (DTC) and 6 patients with recurrent thyroid cancer. Diagnosis of cancer was based on FNAC and histopathology of surgical specimens. All subjects had TSHR/Tg-mRNAs in peripheral blood measured by reverse transcriptase (RT)-PCR. Based on cytology/pathology; 18 patients had newly diagnosed DTC and 11 had benign thyroid disease. Preoperative FNAC was performed on 29 of 40 patients; FNAC was diagnostic in 11/18 of malignant lesions (61.1%), in 8/11 of benign lesions (72.7%), while 10/29 (34.5%) were indeterminate. TSHR/Tg-mRNAs correctly diagnosed DTC in 20/24 and 19/24 (sensitivity 83.3% and 79.1%) and benign disease in 14/16 and 13/16 (specificity 87.5% and 81.3%), respectively. With indeterminate FNA, TSHR/Tg-mRNAs correctly diagnosed DTC (follicular type) in 5/7 and benign disease in 2/3 (combined sensitivity 71.4%; specificity 66.7%). There was high concordance between RT-PCR results for TSHR-mRNA and Tg-mRNA. Of the controls 19/20 (95%) and 16/20 (80%) were negative for both TSHR- and Tg-mRNAs. With the use of a carefully selected primer pair and qualitative RT-PCR; our results indicate that TSHR/Tg-mRNAs in peripheral blood are both equally sensitive and specific markers for detection of thyroid cancer cells. Combining TSHR/Tg-mRNAs and FNAC and ultrasound enhances the preoperative detection of cancer in patients with thyroid nodules, reducing unnecessary surgeries and correctly classified most follicular cancers and could have spared surgery in patients with benign disease.

Keywords: Differentiated thyroid Cancer; TSHR/Tg-mRNAs; Fine-needle aspiration cytology; Thyroid nodules; Indeterminate lesions; Molecular marker