What is the management approach for a patient with Thyroid TIRADS (Thyroid Imaging, Reporting and Data System) 4 lesions?

Management of Thyroid TIRADS 4 Lesions

For thyroid nodules classified as TIRADS 4, fine needle aspiration biopsy (FNAB) is recommended as the standard management approach due to the 5-80% risk of malignancy in this category. 1

Risk Assessment and Initial Management

• TIRADS 4 thyroid nodules represent a moderate-to-high suspicion for malignancy with reported risk ranging from 5-80%, necessitating further evaluation 1
• The primary management approach for TIRADS 4 lesions is ultrasound-guided fine needle aspiration biopsy (FNAB) to determine cytological characteristics 2, 3
• Size criteria should be considered when determining the need for FNAB:
  • Nodules ≥1 cm in size classified as TIRADS 4 should undergo FNAB 2
  • For subcentimeter (<1 cm) TIRADS 4 nodules, surveillance is generally recommended rather than immediate FNAB, unless high-risk features are present 2

Special Considerations for Subcentimeter TIRADS 4 Nodules

• For subcentimeter TIRADS 4 nodules, FNAB is warranted in the following scenarios:
  • Subcapsular location (close to thyroid capsule) 2
  • Presence of suspicious metastatic neck lymph nodes 2
  • Nodules with highly suspicious sonographic features, particularly those <12 mm, as these have shown higher malignancy risk 4

Diagnostic Accuracy and Follow-up

• The sensitivity of TIRADS 4 classification for detecting malignancy is approximately 80-91%, with specificity ranging from 47-53% 4, 3
• When FNAB results are reported using the Bethesda System, there is approximately 83% concordance between TIRADS 4 classification and cytology findings 5
• If FNAB yields benign cytology (Bethesda II) but the nodule has highly suspicious sonographic features (TIRADS 4 or 5), consider repeat FNAB as approximately 14% of such cases may still harbor malignancy 3

Pitfalls and Considerations

• Hyperfunctioning thyroid nodules (HTNs) may be misclassified as TIRADS 4 based on sonographic features alone, with over 80% of HTNs being classified as TIRADS 4A or higher 6
• Consider thyroid scintigraphy for nodules with suspicious sonographic features but normal or low TSH to avoid unnecessary FNAB of hyperfunctioning nodules, which rarely harbor malignancy 6
• An inverse relationship exists between nodule size and malignancy risk; smaller TIRADS 4 nodules (<12 mm) may carry higher malignancy risk than larger ones 4

Management Algorithm

1. For TIRADS 4 nodules ≥1 cm: Proceed with ultrasound-guided FNAB 2, 3
2. For TIRADS 4 nodules <1 cm:
   • If subcapsular location or suspicious lymph nodes present: Proceed with FNAB 2
   • If no high-risk features: Ultrasound surveillance at 6-12 month intervals 2
3. For all TIRADS 4 nodules with normal or low TSH: Consider thyroid scintigraphy before FNAB to rule out hyperfunctioning nodules 6
4. After FNAB, management is guided by Bethesda classification:
   • For benign cytology with highly suspicious sonographic features: Consider repeat FNAB 3
   • For indeterminate or suspicious cytology: Surgical consultation is warranted 3, 5