A 26-year-old man presents with a 3-cm, right lobe, thyroid nodule and a normal TSH. What is the next test that should be performed?

A 26-year-old man presents with a 3-cm, right lobe, thyroid nodule and a normal TSH. What is the next test that should be performed?

• A. FNA of the nodule
• B. Free T4 level
• C. Thyroid ultrasound
• D. Thyroid scan

Answer: (A)

The key idea is that once a thyroid nodule is found in a patient who is euthyroid, the most informative step to determine cancer risk is to obtain a tissue diagnosis. A 3-cm solitary nodule has enough size to raise concern for malignancy, so performing a fine-needle aspiration biopsy provides cytology that can differentiate benign from malignant lesions. This direct diagnostic information guides whether to proceed to surgery or continue observation. A normal Free T4 won’t change management because thyroid function is already normal (TSH is not driving the issue). Thyroid ultrasound is valuable for characterizing the nodule and planning biopsy, but it does not itself diagnose cancer. A thyroid scan assesses functional status (hot vs cold nodules) and is not diagnostic for malignancy, and is not necessary when TSH is normal.

The key idea is that once a thyroid nodule is found in a patient who is euthyroid, the most informative step to determine cancer risk is to obtain a tissue diagnosis. A 3-cm solitary nodule has enough size to raise concern for malignancy, so performing a fine-needle aspiration biopsy provides cytology that can differentiate benign from malignant lesions. This direct diagnostic information guides whether to proceed to surgery or continue observation.

A normal Free T4 won’t change management because thyroid function is already normal (TSH is not driving the issue). Thyroid ultrasound is valuable for characterizing the nodule and planning biopsy, but it does not itself diagnose cancer. A thyroid scan assesses functional status (hot vs cold nodules) and is not diagnostic for malignancy, and is not necessary when TSH is normal.