Thyroid nodule with indeterminate cytology, role of circulating anti-thyroid antibodies

Thyroid nodules are highly prevalent and a common clinical problem worldwide. Fine-needle aspiration (FNA) biopsy is the most widely used diagnostic technique for assessing the cytopathology of thyroid nodules to identify those patients who have nodules that should be excised. The outcome of the cytological exam is imperative in the choice of the approach to have towards a nodule. However, the unsatisfactory non-diagnostic and indeterminate cytology rates, which corresponds to the cytology of approximately 20% of the nodules found at FNA, can lead, in some cases, to unnecessary treatment of thyroid nodules with thyroidectomy. Since only a small part of these nodules end up being thyroid cancer, the challenge for clinicians and pathologists is the management of these nodules, and the choice between surgical excision or active surveillance of the nodule can be a difficult one. Hashimoto thyroiditis (HT) is frequently observed as a coexistent entity with thyroid nodules. The presence of HT can cause typical alterations in FNA, including an increase in immunological infiltrate and cellular atypia. The aim of this study is to evaluate whether HT can influence the accuracy of cytopathological diagnosis of nodules at FNA. Our hypothesis is that the autoimmune process in Hashimoto’s Thyroiditis could induce follicular cell changes that might represent a confounding factor for the determination of cytology, potentially leading to an increased rate of indeterminate cytological results in thyroid nodules which end up to be benign at histology. We searched for patients amongst the outpatients Data Base of the Unit of Endocrinology of ICS Maugeri (Pavia, Italy), retrospectively considering those who underwent a diagnostic work-up for thyroid nodules between January 2017 and December 2019, received a cytological diagnosis of indeterminate cytology and were afterwards submitted to thyroid surgery. The results revealed that patients with an indeterminate cytology had similar rates of thyroid tumours at histology, without any relation to the presence or absence of HT. This study also demonstrates that a concomitant HT does not impair the accuracy of cytological results and therefore does not predispose to a higher rate of diagnosis of indeterminate cytology.