Histologic Evaluation of Thyroid Nodules Treated with Thermal Ablation: An Institutional Experience

Abstract

Thyroid nodules are a common, benign condition with a higher prevalence in women, individuals with iodine deficiency, and radiation exposure. Treatment options for benign thyroid nodules include pharmaceutical therapy, thyroidectomy, and thermal ablation (TA). TA, including laser ablation (LA), radiofrequency ablation (RFA), and microwave ablation (MWA), is a procedure that uses heat to cause tissue necrosis. It is commonly used for large, firm, benign, non-functioning thyroid nodules that cause severe symptoms or pain when surgery is not recommended or desired. When thyroid nodules do not respond to TA, they undergo surgery to resolve the symptoms and clarify the diagnosis. This study aims to analyze the histological alterations found in surgically excised TA-treated thyroid nodules and to evaluate the morphological criteria of differential diagnosis between benign and malignant nodules, establishing whether the alterations observed on the histological sample are a consequence of TA or indicative of neoplastic disease. For this purpose, the adoption of ancillary methods, such as immunohistochemistry, is fundamental to distinguish the artifacts induced by TA from the typical morphological characteristics of malignant neoplasms.

Keywords: differential diagnosis; histological examination; thermal ablation; thyroid nodules.

Figure 1

Histopathological findings of TA-treated thyroid nodules showing the presence of a fibrous capsule ((A), hematoxylin and eosin staining, 50× magnification; scale bar, 168 µm), follicular architecture ((B), hematoxylin and eosin staining, 100× magnification; scale bar, 84 µm), solid architecture ((C), hematoxylin and eosin staining, 100× magnification; scale bar, 84 µm), necrosis ((D), hematoxylin and eosin staining, 50× magnification; scale bar, 168 µm), sclerosis ((E), hematoxylin and eosin staining, 100× magnification; scale bar, 84 µm), hemorrhagic ((F), hematoxylin and eosin staining, 50× magnification; scale bar, 168 µm) and ischemic phenomena ((G), hematoxylin and eosin staining, 50× magnification; scale bar, 168 µm), dark ((H), hematoxylin and eosin staining, 100× magnification; scale bar, 84 µm) and clear nuclei ((I), hematoxylin and eosin staining, 200× magnification; scale bar, 42 µm). Oncocytic cells are visible at different magnifications in panels (A–C). TA: thermal ablation.

Figure 2

Immunohistochemical analysis of a focus of structural disarray in the only TA-treated nodule that tested positive for HBME-1 ((A), 100× magnification; scale bar, 84 µm). Ki-67 was less than 3% ((B), 200× magnification; scale bar, 42 µm). TA: thermal ablation.