From the Guidelines
Thyroid nodules larger than 1 cm should be considered for biopsy, especially if they have suspicious ultrasound features, as recommended by the most recent and highest quality study 1. When evaluating thyroid nodules, it's essential to consider their size, appearance on ultrasound, and risk factors.
- Nodules larger than 1 cm should be biopsied, especially if they have suspicious ultrasound features such as hypoechogenicity, microcalcifications, absence of peripheral halo, irregular borders, and regional lymphadenopathy.
- Solid nodules measuring 1-1.5 cm or larger with high-risk features (irregular margins, microcalcifications, taller-than-wide shape) should be biopsied.
- Nodules without suspicious features may not require biopsy until they reach 1.5-2 cm.
- Very large nodules (over 4 cm) typically warrant biopsy regardless of appearance due to higher cancer risk.
- Smaller nodules under 1 cm generally don't require biopsy unless they have highly suspicious features or the patient has risk factors like radiation exposure or family history of thyroid cancer. The recommendation for biopsy is based on balancing the risk of missing a cancer against performing unnecessary procedures, as most thyroid nodules (about 90-95%) are benign, as noted in 1 and 1. Regular monitoring with ultrasound is appropriate for nodules that don't meet biopsy criteria, with follow-up intervals determined by the nodule's characteristics, as suggested in 1, 1, and 1. It's crucial to prioritize the single most recent and highest quality study, which in this case is 1, to ensure the best possible outcome in terms of morbidity, mortality, and quality of life.
From the Research
Thyroid Nodule Size and Biopsy
- The decision to perform a biopsy on a thyroid nodule is based on various factors, including the nodule's size, ultrasound characteristics, and patient's overall health 2.
- According to the Society of Radiologists in Ultrasound, biopsy should be performed on a nodule 1 cm in diameter or larger with microcalcifications, 1.5 cm in diameter or larger that is solid or has coarse calcifications, and 2 cm in diameter or larger that has mixed solid and cystic components 3.
- The American Association of Clinical Endocrinologists recommends biopsying a hypoechoic nodule with at least one additional feature, such as irregular margins, length greater than width, and microcalcifications 3.
- A study comparing three sets of guidelines for fine-needle aspiration biopsy of thyroid nodules found that the Kim and American Association of Clinical Endocrinologists criteria are more accurate than the Society of Radiologists in Ultrasound criteria 3.
- The presence of microcalcifications is a significant predictor of malignant cytology and histology, especially in nodules with indeterminate cytology 4.
Ultrasound Characteristics and Biopsy
- Ultrasound characteristics such as low echodensity, microcalcifications, irregular borders, and intense vascularization are important predictors of malignancy 5.
- Microcalcifications have a positive predictive value of 3.65 for malignancy, while irregular borders have a positive predictive value of 3.76 5.
- Fine-needle aspiration biopsy is an important tool for diagnosing malignant tumors early, and it helps prevent unnecessary thyroid surgery 5.
Molecular Testing and Biopsy
- Molecular testing can improve the accuracy of cytomolecular testing for thyroid fine-needle aspirations, especially in cases with indeterminate cytology 6.
- Commercially available molecular tests can help guide the need for and extent of thyroid surgery, but they have limitations and should be used appropriately 6.