Interpreting thyroid fine-needle aspiration biopsy

Abstract

One of the most commonly seen abnormalities of the thyroid gland is the thyroid nodule. A thorough clinical evaluation of the nodule includes careful history taking and physical examination, laboratory tests, neck ultrasound (US), and fine-needle aspiration (FNA). Although thyroid FNA serves as an important test with an accurate result, when paired along with US, the results obtained are superior to that obtained only with an FNA. Thyroid FNA or biopsy is an accurate test for determining malignancy in a nodule and is an integral part of current thyroid nodule evaluation. Results are superior when FNA is performed with ultrasound guidance. FNA results are classified as diagnostic (satisfactory) or nondiagnostic (unsatisfactory). The hypocellular specimens produce unsatisfactory or nondiagnostic smears whereas satisfactory or diagnostic smears are categorized as benign, indeterminate, or malignant. In this article, we describe the indications and interpretation of thyroid fine-needle aspiration cytology. The Bethesda Cytologic Classification has a 6-category classification and has been described in the text.