Approach to the adult with a thyroid nodule with indeterminate cytology

FNA: fine-needle aspiration; AUS: atypia of undetermined significance; TSH: thyroid-stimulating hormone; miRNA: microRNA; T4: thyroxine; T3: triiodothyronine.

* Mutational analysis is also possible (80% success rate) by scraping a sample off cytology slides if the cellular material has at least 200 to 300 cells.

¶ If the TSH is subnormal (indicating overt or subclinical hyperthyroidism) and the nodule shows AUS with architectural atypia or follicular neoplasm, the possibility that the nodule is hyperfunctioning is increased, and thyroid scintigraphy should be obtained (if not previously performed) prior to repeating FNA. Some experts also perform thyroid scintigraphy if the TSH is in the lower end of the normal range (eg, <1 mU/L), as thyroid hormone production from some autonomous nodules may suppress TSH only within the lower portion of the normal range. Autonomous nodules rarely are cancer, and a nodule that is hyperfunctioning on radioiodine imaging does not require repeat (or even initial) FNA.

Δ If TSH is below the lower limit of reference range, also measure free T4 and total T3. Refer to UpToDate content on diagnosis and treatment of hyperthyroidism.

◊ Refer to UpToDate content on thyroid scintigraphy.

§ If not already performed, assess the need for thyroid scintigraphy before proceeding to diagnostic surgery. Autonomous nodules are rarely cancerous, and diagnostic surgery would not be indicated. For patients in whom diagnostic surgery is indicated, the decision to perform lobectomy or total thyroidectomy is based upon clinical grounds (eg, size, growth pattern) and/or sonographic features.