What is the first step in the workup of a thyroid nodule after history and physical examination?

The first step in the workup of a thyroid nodule, following a thorough history and physical examination, is fine needle aspiration (FNA). This procedure is vital because it allows for the cytological evaluation of the nodule, which helps in determining whether the nodule is benign or malignant. Given that a significant number of thyroid nodules are asymptomatic and benign, FNA is essential in stratifying the risk of cancer and guiding further management.

Fine needle aspiration is preferred due to its minimally invasive nature, rapid results, and ability to accurately diagnose thyroid pathology. If the FNA yields atypical or suspicious results, further investigations, such as imaging or surgical intervention, may be required. This diagnostic approach is critical in the management of thyroid nodules and significantly influences patient outcomes.

Thyroid imaging and serum thyroid function tests may be performed subsequently but are not the first step in the workup. Imaging can help in assessing the structure of the nodule, and serum thyroid function tests provide information about thyroid hormone levels, but neither gives direct insights into the nodule's cellular makeup. Referral to a specialist may be considered for complex cases or if surgical intervention is indicated, but the definitive initial step remains FNA to evaluate the nodule cytologically.