Nucleic acid recovery from thyroid fine-needle cytology slides Ácidos nucleicos extraídos de lâminas com citologia de punção de agulha fina de tiroide

uch interest has been focused in nucleic acid isolation from tissue samples sto-red for long periods and their utilization on molecular biomarkers research. However, sample fixation induces chemical modifications in macromolecules (1) that result in a laborious and difficult protocol to extract nucleic acid for molecular analy-sis. In this context, the article recently published by Kizys and cols. (2) contributed to show efficient methods of nucleic acid recovery from archived formalin-fixed/ pa-raffin-embedded (FFPE) and fine-needle aspiration (FNA) samples of thyroid tissue.Despite the efforts, the issue that remains a challenge in the most effective protocols is to obtain better yield and quality of DNA/RNA due to the damaging effect of the fixation process, particularly for RNA analysis. In contrast with the difficulty in obtaining conserved messenger RNA from archived samples, the fraction of microRNA (miRNA) is less affected by fixation and storage time (3,4). Mature miRNA is a single-stranded noncoding small RNA of ~19-22 nucleotide length that regulates gene expression at the post-transcriptional level (5). These molecules pair to 3’UTRs of target mRNA and thereby cause their silencing or degradation. The miRNA might be a promising prognostic and diagnostic biomarker for thyroid cancer (6).In this context, we have performed, in archived FNA-stained slides, the analysis of