Which features of a thyroid nodule warrant a fine-needle aspiration (FNA)?

Fine-needle aspiration (FNA) of a thyroid nodule is primarily indicated based on certain ultrasound characteristics that are associated with a higher risk of malignancy. The presence of solid composition, hypoechogenicity, and microcalcifications, as indicated in the correct answer, are all features that elevate the concern for thyroid cancer.

Solid nodules are of particular interest because, in contrast to cystic (fluid-filled) nodules, they have a higher likelihood of harboring malignancy. Hypoechoic nodules, those appearing darker than surrounding tissues on ultrasound, are also an important characteristic since they tend to be more suspicious for cancer. Furthermore, microcalcifications, which appear as tiny bright spots on ultrasound, can be indicative of malignancy, particularly papillary thyroid carcinoma. The combination of these features—being solid, hypoechoic, and having microcalcifications—strongly warrants the need for FNA to rule out cancer.

In contrast, nodules that are fluid-filled and exhibit symmetric growth may suggest a benign cyst rather than a malignant process, therefore not necessitating FNA. Hypoechoic nodules with regular margins might be less concerning when evaluated in the context of other benign features. Finally, calcified nod