Thyroid Nodules: When to Biopsy?

A 55-year-old woman comes to your office and tells you that she has been worried about a “lump in her throat” for the past 3 months. You examine her neck and find a firm mobile nodule (1 cm in diameter) in the thyroid area.

The patient has a history of mantle field radiation for a childhood cancer. Her TSH level is normal. You refer her for ultrasonography, which shows a 1.2-cm hypoechoic solid nodule.

In this patient-with a solid hypoechoic nodule larger than 1 cm on an ultrasonogram and a high-risk clinical feature (ie, a history of radiation therapy), immediate referral for a fine-needle aspiration biopsy is warranted.

Discussion
Palpable thyroid nodules occur in 4% to 7% of the population (10 to 18 million persons). However, the prevalence of nodules found incidentally on ultrasonography may be as high as 67%.^1,2 Thyroid carcinoma is ultimately found in roughly 5% to 10% of palpable nodules.¹ Accurate diagnosis of thyroid nodules is thus critical to the detection of thyroid carcinoma.

There are currently 3 sets of guidelines for the management of thyroid nodules that have been published during the past 4 years:
• The American Thyroid Association (ATA)³
• The American Association of Clinical Endocrinologists (AACE), in collaboration with the Associazione Medici Endocrinologi (AME) and the European Thyroid Association (ETA)⁴
• The Korean Society of Thyroid Radiology (KSTR)⁵  

There is some overlap among these guidelines, but there are also significant differences.

Comparisons
The AACE-AME-ETA guidelines recommend biopsy of any solid and hypoechoic nodule larger than 1 cm in diameter. Other high-risk features that necessitate a biopsy include a history of irradiation, a family history of medullary carcinoma or multiple endocrine neoplasia syndrome, a history of partial thyroidectomy for thyroid cancer, or presence of an elevated calcitonin level.

The ATA guidelines recommend against biopsy for thyroid nodules smaller than 5 mm in diameter. Biopsy of solid nodules smaller than 1 cm is discouraged if no clinical risks or microcalcifications are present. Similarly, the AACE guidelines do not recommend biopsy of solid nodules that are smaller than 1 cm in diameter if the patient has no clinical risks and there are no suspicious features on an ultrasonogram. Nodules that appear hyperfunctioning on scintigraphy can also escape biopsy.

References
1. Mazzaferri EL. Thyroid cancer in thyroid nodules: finding a needle in the haystack. Am J Med. 1992;93:359–362.
2. Gharib H, Goellner JR. Fine-needle aspiration biopsy of the thyroid: an appraisal. Ann Intern Med. 1993;118:282–289.
3. Cooper DS, Doherty GM, Haugen BT, et al; American Thyroid Association [ATA] Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2009;19:1167–1214.
4. Gharib H, Papini E, Paschke R, et al; AACE/AME/ETA Task Force on Thyroid Nodules. American Association of Clinical Endocrinologists, Associazione Medici Endocrinologi, and European Thyroid Association medical guidelines for clinical practice for the diagnosis and management of thyroid nodules. Endocr Pract. 2010;16(suppl 1):1–43.
5. Moon WJ, Baek JH, Jung SL, et al; Korean Society of Thyroid Radiology [KSThR; Korean Society of Radiology. Ultrasonography and the ultrasound-based management of thyroid nodules: consensus statement and recommendations. Korean J Radiol. 2011;12:1–14.