A thyroid nodule is found on a 40-year-old woman on routine evaluation. She has no prior history of thyroid disease and clinically feels well. There is a 15-mm nontender nodule on the right lobe of the thyroid with no associated lymphadenopathy. Thyroid function tests are normal. Which of the following is the most appropriate next step in management?

Needle biopsy can be used in numerous diseases, but the main rationale is to differentiate benign from malignant nodules. A thyroid scan is appropriate if the TSH is suppressed suggesting a possible "hot" nodule (hyperfunctioning nodules are very rarely malignant). The specimen must be read by an experienced cytologist. It is difficult to diagnose differentiated follicular carcinoma or to differentiate lymphoma from Hashimoto's thyroiditis. Papillary carcinoma is the easiest diagnosis to make by needle biopsy.