Does Radiofrequency Ablation Induce Neoplastic Changes in Benign Thyroid Nodules: A Preliminary Study

Abstract

Background: To evaluate the clinical feasibility of radiofrequency ablation (RFA) of benign thyroid nodules along with cytomorphological alteration, and any malignant transformation through biopsy.

Methods: The data were retrospectively collected between April 2008 and June 2013 and core needle biopsy (CNB) was performed on 16 benign thyroid nodules previously treated using RFA. The parameters of the patients were compared, between the time of enrollment and the last follow-up examination, using linear mixed model statistical analysis.

Results: No atypical cells or neoplastic transformation were detected in the undertreated peripheral portion of treated benign nodules on the CNB specimen. RFA altered neither the thyroid capsule nor the thyroid tissue adjacent to the treated area. On histopathological examinations, we observed 81.2% acellular hyalinization, which was the most common finding. After a mean follow-up period of over 5 years, the mean volume of thyroid nodule had decreased to 6.4±4.2 mL, with a reduction rate of 81.3%±5.8% (P<0.0001).

Conclusion: RFA is a technically feasible treatment method for benign thyroid nodules, with no carcinogenic effect or tissue damage of the normal thyroid tissue adjacent to the RFA-treated zone.

Keywords: Biopsy, large-core needle; Pathology; Radiofrequency ablation; Thyroid nodule; Ultrasonography.

Fig. 1. Orientation of the thyroid core needle biopsy. (A) Normal thyroid tissue is noted on the left lower corner (blue arrow). (B) Less than half near the normal thyroid tissue is defined as ‘peripheral’ (red arrow, A). (C) More than half distance from the normal thyroid tissue is defined as ‘central’ (black arrow, A) with focal remaining benign follicular lesion on the central side (H&E stain, ×100).

Fig. 2. Treatment effect after radiofrequency ablation (RFA) of a benign follicular nodule. (A) Note acellular dense hyalinization (black arrow) and the remaining benign follicular lesion (red arrow) (×40). (B) The remaining benign follicular lesion shows mixed benign thyroid follicles with variable sizes and nuclear enlargement without nuclear atypia at higher magnification (H&E stain, ×200).

Fig. 3. Coexistence of the slightly viable area and totally infarcted area after radiofrequency ablation (RFA). (A) Slightly viable area (black arrow) and totally infarcted area after RFA (red arrow) (H&E stain, ×100). (B) Immunohistochemical (IHC) staining for the human mitochondria antibody. Both viable and totally infarcted areas are negative for human mitochondria antibody (×100). IHC stains for (C) thyroglobulin and (D) thyroid transcription factor-1 (TTF-1). The totally infarcted area shows loss of expression for thyroglobulin and TTF-1, whereas the slightly viable area is positive for both (×100).