## 2 Materials and Methods
### Immunolistochemistry  
Immunohistochemical experiments were performed on 5-micron thick sections of paraffin-embedded tissue, obtained with a cutting microtome. The slides were dewaxed in xylene for 30 min at 60 \({}^{\circ}\)C and rehydrated, at 22 \({}^{\circ}\)C, by sequential immersion in a graded series of alcohols and transferred into distilled water for 5 min. Then, the sections were incubated for 8 min in Sodium Citrate Buffer (pH 6) at 95 \({}^{\circ}\)C for antigen unmasking and immersed for 8 min in acetone at \(-\)20 \({}^{\circ}\)C to prevent the detachment of the sections from the slide. After a wash of sections with PBS (Phosphate Buffered Saline pH 7.4) at 22 \({}^{\circ}\)C for 5 min, the experiments for Hsp60, Hsp70, and Hsp90 were performed applying a streptavidin-biotin complex method, using Histogram(r)-Plus 3 rd Gen IHC Detection Kit (Life Technologies, Frederik, MD, USA; Cat. No. 85-9073). Therefore, the sections were treated for 5 min with Peroxidase Quenching Solution (reagent A of Histostain(r)-Plus 3 rd Gen IHC Detection Kit, Life Technologies) to inhibit endogenous peroxidase activity, and after another wash with PBS at 22 \({}^{\circ}\)C for 5 min, were treated with blocking solution (reagent B of Histostain(r)-Plus 3 rd Gen IHC Detection Kit, Life Technologies) for 10 min to block non-specific antigenic sites. Subsequently, the sections were incubated overnight at 22 \({}^{\circ}\)C, with a primary antibody against human Hsp60 (rabbit anti-Hsp60 polyclonal antibody, Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA, cat. N\({}^{\circ}\): sc-13966, dilution 1:300), human Hsp70 (mouse anti-Hsp70 monoclonal antibody, clone W27, Santa Cruz Biotechnology, Inc, Santa Cruz, CA, USA, cat. N\({}^{\circ}\): sc-24, dilution 1:200) and human Hsp90 (mouse anti-Hsp90 monoclonal antibody, clone F-8, Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA, cat. N\({}^{\circ}\): sc-13119, dilution 1:200). Appropriate positive and negative (isotype) controls, were run concurrently. The following day, after a wash with PBS at 22 \({}^{\circ}\)C for 5 min, the sections were incubated with a universal \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sex** & **Age (yrs)\({}^{*}\)** & **Localization** & **Thyroid Weight** & **Nodules Size** \\  & & & **(g)** & **(mm)** \\ \hline \multicolumn{5}{c}{**FOLICULAR ADENOMA**} \\ \hline M & 27 & Right lobe & 35 & 17 \\ F & 39 & Right lobe & 15 & 28 \\ F & 69 & Left lobe & 30 & 24 \\ M & 46 & Right lobe & 35 & 32 \\ F & 73 & Left lobe & 120 & 30 \\ F & 55 & Left lobe & 20 & 20 \\ F & 67 & Right lobe & 40 & 22 \\ M & 35 & Left lobe & 55 & 38 \\ F & 29 & Isthmus & 60 & 42 \\ F & 48 & Right lobe & 70 & 15 \\ \hline \multicolumn{5}{c}{**FOLICULAR CARCINOMA**} \\ \hline F & 41 & Left lobe & 45 & 25 & I \\ F & 29 & Right lobe & 35 & 30 & I \\ M & 62 & Right lobe & 80 & 35 & I \\ F & 51 & Right lobe & 50 & 40 & I \\ F & 48 & Isthmus & 20 & 28 & I \\ F & 39 & Left lobe & 25 & 25 & I \\ M & 67 & Right lobe & 45 & 38 & II \\ F & 57 & Right lobe & 60 & 22 & II \\ F & 29 & Left lobe & 25 & 19 & I \\ F & 61 & Right lobe & 30 & 41 & I \\ \hline \multicolumn{5}{l}{*Abbreviations. Yrs, years; M, male; F, female; AJCC, American Joint Committee on Cancer; TNM, Tumor-Nodes-Metastasis.} \\ \end{tabular}
\end{table} 
Table 1: Patient demographics and tumor characteristics. botinylated secondary antibody (Botinylated Secondary Antibody reagent C Histogram(r)-Plus 3 rd Gen IHC Detection Kit, Life Technologies) for 10 min. After a subsequent washing with PBS for 5 min, the sections were incubated with streptavidin-peroxidase complex (Streptavidin-Pervidase Conjugate reagent D Histogram(r)-Plus 3 rd Gen IHC Detection Kit, Life Technologies) for 10 min, and following a further washing in PBS for 5 min, the slides were incubated in the dark for 5 min with the DAB chromogen (diaminobenzidine) (DAB chromogen reagents E1 and E2 Histogram(r)-Plus 3 rd Gen IHC Detection Kit, Life Technologies).