In a patient with a solitary thyroid nodule who is clinically and chemically euthyroid, what is the next best diagnostic step?

• A. Reassure the patient and reassess yearly.
• B. Recheck in 1-3 months.
• C. Fine needle aspiration.
• D. CT neck

Answer: (C)

The key idea is to determine whether a solitary thyroid nodule is malignant or benign, since solitary nodules carry a higher cancer risk than multinodular ones. Obtaining tissue for cytology with a fine-needle aspiration biopsy provides the most direct and clinically useful diagnosis to guide management without surgery. In a patient who is clinically and biochemically euthyroid, there’s no need to assess thyroid function here, and imaging alone cannot reliably differentiate cancer from benign nodules. Reassuring the patient or scheduling a simple recheck misses the opportunity to detect malignancy early, and CT neck does not sample tissue and adds unnecessary radiation. Therefore, fine-needle aspiration is the best next diagnostic step, typically performed under ultrasound guidance to ensure accurate sampling.