Background: The Korea Thyroid Association published the revised guidelines for thyroid nodules in 2016. However, whether fine-needle aspiration is accurately performed based on indications and whether the results of this procedure are appropriately addressed according to clinical guidelines, particularly in subcentimeter nodules, are unclear. Methods: We retrospectively analyzed the fine-needle aspiration data of 331 thyroid nodules of patients who were referred to a tertiary hospital clinic for fine-needle aspiration. Each nodule was categorized according to ultrasonography findings based on the recommendations of the Korea Thyroid Association for fine-needle aspiration. Only nodules with a final pathological diagnosis of benign or malignant made using the Bethesda system were included. Results: Up to 32% of thyroid nodules that were not indicated for fine-needle aspiration were aspirated. Regarding subcentimeter nodules, only 28 of 123 (22.8%) aspirated nodules were indicated for fine-needle aspiration. Of the 49 malignant subcentimeter nodules, 33 (67.3%) underwent immediate surgery. Meanwhile, 14 (28.6%) nodules were lost to followup, and two (4.1%) were under active surveillance. Eighteen (36.7%) malignant subcentimeter nodules were not indicated for fine-needle aspiration but underwent surgical resection instead of active surveillance. Conclusion: Despite the recommendations in the revised guidelines, several thyroid nodules that do not meet the indications for FNA are aspirated in real-world practice. To reduce overtreatment, a widespread knowledge of the correct indications for fine-needle aspiration is important in clinical practice, particularly for subcentimeter nodules.

Key Clinical MessageAgranulocytosis is a rare side effect of antithyroid drugs (ATD) that usually develops within the first 3‐6 months after starting treatment. We present a 64‐year‐old patient who developed agranulocytosis after starting ATD to treat relapsed Graves' disease. This patient had tolerated the first course of ATD for 72 months. This was an unusual case in which a serious side effect developed during a second ATD course. It is essential that clinicians remain vigilant to the fact that antithyroid drugs can induce agranulocytosis several years after initiated.

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