ATA Guidelines
The ATA guidelines, revised in 2009, begin by asking whether the patient has a history suggestive of a high risk for thyroid cancer. Risk factors include radiation exposure during childhood, rapid growth of a nodule, hoarseness, vocal cord paralysis, dysphagia, or a family history of thyroid cancer or multiple endocrine neoplasia syndrome. If the patient has a high-risk history, the recommendation is to obtain a biopsy specimen from any thyroid nodule larger than 5 mm in diameter with suspicious features.
For patients without a high-risk history, the guidelines then ask whether abnormal cervical lymph nodes are present, detected by either physical examination or ultrasound study. If so, biopsy samples should be obtained from the lymph nodes themselves, with or without biopsy of any suspicious thyroid nodules present.
Microcalcifications have a high specificity for papillary cancer. Thus, biopsy is recommended for any nodule exhibiting microcalcifications and measuring more than 1 cm.
For those patients without a high-risk history, abnormal lymph nodes, or microcalcifications, the ATA guidelines then divide the thyroid nodules into categories on the basis of their composition. Nodules are characterized as entirely solid, mixed cystic-solid, spongiform, or purely cystic. Biopsy is recommended for all solid hypoechoic nodules that exceed 1 cm in diameter. Isoechoic or hyperechoic nodules exceeding 1 to 1.5 cm should undergo biopsy. Biopsy is recommended for mixed cystic-solid nodules that exceed 1.5 to 2 cm, if they have irregular margins, microcalcifications, or infiltration of the surrounding tissue. The recommendation for mixed cystic-solid nodules without suspicious ultrasonographic features is for biopsy if they are larger than 2 cm. Those nodules exhibiting a spongiform echotexture should undergo biopsy only if they are larger than 2 cm in diameter. Finally, purely cystic nodules do not require biopsy under the ATA guidelines.