The Thyroid Imaging Reporting and Data System (TIRADS) is a standardized method used by radiologists to describe and assess thyroid nodules found during an ultrasound examination. This classification system brings consistency to reporting, helping doctors determine which nodules require further investigation and which can be safely monitored. Thyroid nodules are extremely common, but the vast majority are benign. TIRADS provides a risk-stratified approach to identify the small percentage of nodules that may be cancerous, reducing the number of unnecessary biopsies. By assigning a score based on specific imaging features, the system guides patient care and appropriate surveillance.
Understanding the Nodule Features Used in Classification
Radiologists evaluate five distinct ultrasound characteristics of a thyroid nodule to apply the TIRADS classification.
Composition
Composition describes what the nodule is made of, ranging from purely fluid-filled (cystic) to entirely solid. A completely cystic or largely spongiform nodule, which contains many small fluid-filled spaces, is generally considered benign. Conversely, a solid or almost completely solid nodule is more concerning and receives a higher point value.
Echogenicity
Echogenicity refers to how bright or dark the nodule appears compared to the surrounding healthy thyroid tissue. A nodule that is darker than the adjacent thyroid tissue (hypoechoic) is more suspicious than one that is the same brightness (isoechoic) or brighter (hyperechoic). A very hypoechoic nodule, appearing darker than the neck muscles, is considered highly suspicious.
Shape
Shape is assessed on a transverse image of the nodule. A nodule that is wider than it is tall is a common and reassuring finding. However, a shape that is taller-than-wide is a strong predictor of malignancy and is assigned the highest point value in this category.
Margin
Margin describes the border between the nodule and the surrounding thyroid gland. A smooth or ill-defined margin is usually less concerning and receives zero points. Margins that are lobulated, irregular, or show signs of extending outside the thyroid gland are associated with a higher risk and accumulate points.
Echogenic Foci
Echogenic foci are small, bright spots within the nodule. The presence of tiny, non-shadowing, punctate echogenic foci is the most concerning finding in this category. These often correlate with microcalcifications seen in papillary thyroid cancer.
How the TIRADS Score is Calculated
The TIRADS system uses a point-based approach where points are assigned to each of the five ultrasound features based on their level of suspicion. The score is calculated by selecting one characteristic from the composition, echogenicity, shape, and margin categories, and then adding all applicable findings from the echogenic foci category. For instance, a solid nodule earns 2 points for composition, while a purely cystic nodule earns 0 points.
Features strongly associated with malignancy, such as a taller-than-wide shape or punctate echogenic foci, immediately add 3 points to the total score. The points from all five categories are then summed up to produce a single total score, which translates directly into the final TIRADS category (TR1 through TR5).
- A score of 0 points is classified as TR1.
- A score of 2 points is TR2.
- The score range for TR3 is 3 points.
- TR4 spans 4 to 6 points.
- A score of 7 points or more results in the highest risk category, TR5.
Interpreting the Risk: What Your TIRADS Score Means
The final TIRADS category links the nodule’s ultrasound appearance to an estimated risk of malignancy and a specific management recommendation.
TR1: Benign
A TR1 classification means the nodule is benign, typically consisting of a simple cyst or a completely spongiform nodule. The malignancy risk is less than 1%. These nodules require no fine-needle aspiration (FNA) biopsy and no routine follow-up.
TR2: Not Suspicious
A TR2 nodule is classified as not suspicious, with a malignancy risk estimated to be less than 2%. These findings include nodules with a score of 2 points, such as those that are solid but entirely isoechoic and wider-than-tall. No FNA biopsy or ultrasound follow-up is generally recommended for TR2 nodules unless the nodule is very large.
TR3: Mildly Suspicious
The TR3 category signifies a mildly suspicious nodule, corresponding to a total score of 3 points and an approximate malignancy risk of 4.8%. The recommendation for FNA biopsy is triggered if the nodule reaches a maximum diameter of 2.5 centimeters or larger. If the nodule is between 1.5 and 2.4 centimeters, ultrasound surveillance is recommended at specified intervals.
TR4: Moderately Suspicious
A TR4 nodule is moderately suspicious, with a score between 4 and 6 points and a malignancy risk ranging from 5% to 20%. FNA is recommended if the nodule measures 1.5 centimeters or greater. If the nodule is between 1.0 and 1.4 centimeters, the physician will typically recommend periodic ultrasound surveillance instead of immediate biopsy.
TR5: Highly Suspicious
A TR5 classification indicates a highly suspicious nodule, with a score of 7 points or more and a malignancy risk of 20% to 35%. These nodules often display the most concerning features, such as a taller-than-wide shape or punctate echogenic foci. Due to the significantly elevated risk, FNA biopsy is recommended for TR5 nodules measuring 1.0 centimeter or larger. Even smaller TR5 nodules (0.5 to 0.9 centimeters) are generally advised to undergo ultrasound follow-up.