Fine-needle aspiration biopsy of thyroid nodules as a possible source for molecular studies: analysis of RNA obtained from routine cases.

Thyroid nodules are frequent in clinical practice and fine-needle aspiration biopsy (FNAB) is widely used for its evaluation, but approximately 20% of the cases are diagnosed as indeterminate for malignancy. Aspirates from thyroid nodules can be used for ancillary methods, but molecular techniques are not routinely applied to these specimens. Forty-six consecutive, routinely performed, FNAB of thyroid nodules were evaluated for the feasibility of applying RT-PCR method. RNA was extracted from 1 of 3 fresh residual samples and analyzed to determine its pureness, integrity, and concentration. Cellularity was adequate in all 46, except one, specimens analyzed, scored as 0, 1+, 2+, 3+, and 4+ in 1, 10, 14, 9, and 8 cases, respectively. Thirty-three nodules measured less than 1.5 cm. Cytological diagnosis was positive for malignancy in 3 cases, indeterminate for malignancy in 3, most probably benign follicular lesion in 7, negative for malignancy in 32, and suggestive of benign follicular lesion in 1. Good quality RNA was successfully isolated in 45/46 (97.8%) samples, with an average RNA concentration of 14 ng/microl and detection of B2M mRNA in 97.7% (44/45). There was no significant correlation between RNA concentration and nodule size or specimen cellularity. In conclusion, molecular analysis using individual, residual samples of thyroid nodules aspirates is feasible and could be employed for molecular preoperative studies in the future, adding elements for final cytological diagnosis of indeterminate cases, without altering the routine procedure.