The Significance of Heat Shock Protein 70 Expression in Benign Thyroid Nodules During Thermal Ablation

Objective: To investigate the change of HSP70 expression after microwave ablation of benign thyroid nodules.Method: Ultrasound-guided microwave ablation (MWA) was conducted for treating 60 benign solid thyroid nodules in 60 patients. Three different region of interest (ROI), named as central zone, marginal zone and transitional zone, were artificially set in each nodule for quantitative investigation of HSP70 expression by using the immunohistochemistry (IHC) method based on the US-guided core-needle biopsy (CNB) technique. As a longitudinal comparative study design, each ROI experienced twice histological sampling twice by using CNB before and after MWA. IHC semi-quantitative determination of HSP70 expression was compared among the specimen from the three ROIs in a same nodule before ablation and between the specimen from the same ROI before and after ablation respectively as well.Results: Of the 60 solid thyroid nodules, either in the central zone or in the marginal zone, HSP70 expression did not experienced significant change (P > 0.05) from before ablation to after ablation, however, a significant upgrading of HSP70 expression developed in the transitional zone after ablation (P < 0.05). After ablation, the transitional zone had a higher level of HSP70 than that in both the central and marginal zones (P < 0.05) in a same nodule, while the level of HSP70 was not found significantly different between the central zone and marginal zone (P > 0.05).Conclusion: Thermal coagulation by MWA stimulates the upgrading of HSP70 expression in the heated tissue of benign thyroid nodules, but in a way of regional discrepancies. The remarkable increased expression of HSP70 in the transitional zone tissue might originate from a slower and less intensive temperature rise along with the attenuation of microwave radiation, and it is postulated to protect normal glandular tissue against heat damage. Fast and intensive temperature rise within the nodule causes more intensive and massive thermal coagulation changes and weakens the adequate expression and proper protective function of HSP70 in those two areas.