TIRADS 4: Moderately Suspicious Thyroid Nodules
TIRADS 4 represents thyroid nodules that are "moderately suspicious" for malignancy, with an estimated malignancy risk of 5-80%, and is determined by scoring 4-6 points based on specific ultrasound features including composition, echogenicity, shape, margins, and calcifications. 1
Point-Based Classification System
The ACR TI-RADS uses a standardized point system where you evaluate five ultrasound categories:
- Composition (0-2 points): Solid nodules score highest (2 points), mixed cystic-solid score 1 point
- Echogenicity (0-3 points): Very hypoechoic scores 3 points, hypoechoic scores 2 points, hyperechoic/isoechoic scores 1 point
- Shape (0-3 points): Taller-than-wide configuration scores 3 points
- Margins (0-3 points): Extra-thyroidal extension scores 3 points, lobulated/irregular margins score 2 points
- Echogenic foci (0-3 points): Punctate echogenic foci score 3 points, peripheral rim calcifications score 2 points, macrocalcifications score 1 point
When the total points equal 4-6, the nodule is classified as TR4 (TIRADS 4). 1
Malignancy Risk Stratification
TIRADS 4 is further subdivided based on actual malignancy rates observed in clinical practice:
- TIRADS 4A: 5.88% malignancy rate
- TIRADS 4B: 62.82% malignancy rate
- TIRADS 4C: 91.22% malignancy rate 2
This wide range (5-80%) reflects the heterogeneity within the TR4 category, making it the "intermediate suspicion" group that requires careful clinical judgment.
Clinical Management Recommendations
For TR4 nodules, fine-needle aspiration (FNA) is recommended when the nodule reaches ≥1.5 cm in maximum diameter. 1 This size threshold balances the need to detect clinically significant malignancies while avoiding unnecessary biopsies of small, potentially indolent lesions.
The diagnostic performance when using TR4-5 as the cutoff for recommending FNA demonstrates:
- Sensitivity: 99.6%
- Specificity: 74.35%
- Positive predictive value: 82.1%
- Negative predictive value: 99.4% 2
Common Pitfalls and Caveats
The intermediate suspicion category (TR4) presents diagnostic challenges with lower accuracy compared to other TIRADS categories. Recent data shows radiologist accuracy in this category ranges from 66.4-71.4% without AI assistance, improving to 74.1-79.4% with AI support 3. This highlights that TR4 nodules are inherently more difficult to characterize.
Critical point: The ACR TI-RADS should guide but not replace clinical judgment. The decision to perform FNA must also account for:
- Patient-specific risk factors for thyroid cancer
- Patient anxiety and preferences
- Comorbidities and life expectancy
- Referring physician input 1
Do not apply TIRADS as an absolute standard—it serves as guidance for practitioners, and interpreting physicians retain professional responsibility for applying judgment to each individual case 1.
Key Distinguishing Features
The most suspicious features that push nodules into higher point categories (and thus TR4 territory) include:
- Solid composition
- Hypoechoic or very hypoechoic echogenicity
- Taller-than-wide shape
- Irregular or lobulated margins
- Punctate echogenic foci (microcalcifications) 1
Nodules with microcalcifications and interrupted halo signs are significantly associated with malignancy, while macrocalcifications and complete halo signs favor benign pathology 4, helping refine risk assessment within the TR4 category.