Non-Neoplastic and Indeterminate Thyroid Lesions

Non-neoplastic thyroid lesions include nodules with nondiagnostic cytology and those with benign cytology. In approximately 15% of cases, fine-needle aspiration cytology (FNAC) results in cytologically inadequate specimens. Nondiagnostic smears have an inadequate number of cells to allow a diagnosis. This category also includes cystic lesions, which are a frequent cause of inadequate results. Benign diagnosis represents the most frequent result following FNAC, with a rate of 70%. The most common benign lesions are macrofollicular or adenomatoid/hyperplastic nodules, colloid adenomas, nodular goiter, lymphocytic and granulomatous thyroiditis. The risk of malignancy in these two cytological categories is 1–4% and 0–3%, respectively. The management of these lesions is generally conservative. In about 20–25% of cases, FNAC leads to the diagnosis of indeterminate thyroid nodule. This result represents a clinical issue, since malignancy, although relatively low (up to 30%), cannot be ruled out with certainty. When indicated, surgery has a diagnostic rather than therapeutic purpose, with almost 80% of procedures being unnecessary. In this regard, it is important to emphasize that thyroidectomy can lead to serious complications. For these reasons, there is an increased emphasis on assessing the risk of malignancy of indeterminate nodules to minimize unnecessary surgical procedures.