What are the differences between thyroid nodules classified as level 3 and level 4?
Aug 06, 2025
Source: Cainiu Health
Dr. Yang Ziqi
Introduction
Under normal circumstances, the main differences between thyroid category III and category IV nodules include different risks of malignancy, different ultrasound features, different management approaches, different follow-up frequencies, and differing necessity for biopsy. In daily life, regardless of whether the nodule is category III or IV, it is important to maintain healthy lifestyle habits and avoid excessive fatigue and mental stress.
Generally speaking, the main differences between thyroid nodules classified as category 3 and category 4 include different risks of malignancy, distinct ultrasound characteristics, varied management approaches, differing follow-up frequencies, and varying necessity for biopsy. Detailed analysis is as follows:
1. Different Malignancy Risks: Category 3 nodules are mostly benign, with an extremely low risk of malignancy, usually less than 2%. Category 4 nodules carry a higher risk of malignancy. Category 4 can be further divided into subtypes 4A, 4B, and 4C, with progressively increasing malignancy risks, ranging approximately from 2% to 90%.
2. Different Ultrasound Features: On ultrasound, category 3 nodules typically appear regular in shape, with clear boundaries, no calcifications or only coarse calcifications, homogeneous internal echogenicity, and not rich blood flow signals. Category 4 nodules may exhibit irregular shapes, blurred boundaries, microcalcifications, a height-to-width ratio greater than 1, heterogeneous internal echogenicity, and abnormal blood flow signals.
3. Different Management Approaches: If category 3 nodules are small and asymptomatic, observation is generally recommended without immediate surgery. Due to the higher risk of malignancy, category 4 nodules usually require more proactive evaluation, and in some cases, decisions regarding surgical treatment are made based on pathological findings.
4. Different Follow-up Frequencies: The follow-up interval for category 3 nodules is relatively longer, typically recommending ultrasound reexamination every 6-12 months. For category 4 nodules, the follow-up interval is shorter, usually recommending reexamination every 3-6 months to detect any changes in condition promptly.
5. Different Necessity for Biopsy: Fine-needle aspiration biopsy (FNAB) is generally not required for category 3 nodules unless there is significant enlargement or other abnormalities. Most category 4 nodules require FNAB to determine the pathological nature of the nodule and provide a basis for subsequent treatment.
In daily life, regardless of whether the nodule is categorized as 3 or 4, it is important to maintain good living habits, avoid excessive fatigue and mental stress, eat a balanced diet, and engage in appropriate exercise to maintain thyroid health.
