Management of Incidental Thyroid Mass
The next step after an incidental finding of a thyroid mass should be a dedicated thyroid ultrasound followed by fine-needle aspiration (FNA) of nodules meeting size and suspicious feature criteria. 1
Initial Evaluation
- Thyroid-stimulating hormone (TSH) measurement should be the first laboratory test to assess thyroid function 1
- Dedicated thyroid and central neck ultrasound is essential to characterize the nodule(s) and evaluate for suspicious lymph nodes 1
- Lateral neck ultrasound should be performed if there are concerning features in the thyroid nodule or central neck 1
Ultrasound Characterization
Ultrasound evaluation should assess the following features:
- Size (measured in three dimensions) 2, 3
- Composition (solid, cystic, or mixed) 4, 3
- Echogenicity (hyper-, iso-, or hypoechoic) 2, 3
- Margins (regular vs. irregular/infiltrative) 2, 3
- Presence of calcifications (microcalcifications are more concerning) 2, 3
- Shape (wider-than-tall vs. taller-than-wide) 3
Decision for Fine Needle Aspiration (FNA)
FNA should be performed based on the following criteria:
- Nodules ≥1-1.5 cm with suspicious ultrasound features 1
- Nodules with suspicious lymph nodes regardless of size 1
- Nodules that are PET-positive on prior imaging 1
- Smaller nodules (<1 cm) without suspicious features can be followed clinically without immediate FNA 1
Risk Stratification Systems
The ACR Thyroid Imaging, Reporting and Data System (TI-RADS) should be used to standardize reporting and guide management decisions:
- TI-RADS categorizes nodules based on ultrasound features 3
- Higher TI-RADS scores indicate greater risk of malignancy and lower size thresholds for FNA 3
- This system helps reduce unnecessary biopsies of likely benign nodules 3
Management Based on FNA Results
- Benign cytology: Follow-up with ultrasound at appropriate intervals 1
- Malignant cytology: Total thyroidectomy with or without central neck dissection depending on tumor size and other risk factors 1
- Indeterminate cytology: Consider molecular testing to further stratify risk 1
Special Considerations
- Rapidly growing thyroid masses require urgent evaluation as they may represent aggressive malignancies like anaplastic thyroid carcinoma or lymphoma 5
- Incidental thyroid abnormalities found on other imaging studies (e.g., carotid duplex ultrasonography) should be confirmed with dedicated thyroid ultrasound, which has a high correlation rate (97%) 6
- The majority of thyroid nodules are benign, but proper evaluation is essential to identify the minority that are malignant 1
Common Pitfalls to Avoid
- Overdiagnosis and overtreatment of small, indolent thyroid cancers is a concern; not all nodules require immediate biopsy 1
- Failure to evaluate for functional status with TSH may miss hyperfunctioning nodules that require different management 1
- Inadequate ultrasound assessment may miss important features that influence management decisions 2, 3
- Incomplete neck evaluation may miss regional lymphadenopathy that would change management 1