What are the differences between malignant and benign thyroid nodules classified as TI-RADS 4a?

　　The differences between malignant and benign thyroid nodules of category 4a generally include ultrasound features, growth rate, texture and palpation characteristics, symptom presentation, and pathological results. If abnormalities are detected, timely medical consultation is recommended. Detailed analysis is as follows:

　　1. Ultrasound features: Benign nodules typically appear with regular shape, clear boundaries, uniform internal echogenicity, and less abundant blood flow signals; malignant nodules often show irregular shape, unclear boundaries, uneven internal echogenicity, possible calcifications, and more evident blood flow signals.

　　2. Growth rate: Benign nodules grow slowly, with little noticeable change in size over long-term observation; malignant nodules may significantly increase in a short period, with evident diameter changes within several months.

　　3. Texture and palpation: Benign nodules feel relatively soft upon palpation, have good mobility, and are not adhered to surrounding tissues; malignant nodules feel harder, have poor mobility, are often adhered to surrounding tissues, and show little positional change when pushed.

　　4. Symptom presentation: Benign nodules usually cause no significant discomfort and may only cause a feeling of pressure or swallowing discomfort when large; malignant nodules may invade nerves, causing hoarseness, dysphagia (difficulty swallowing), or accompanied by cervical lymph node enlargement.

　　5. Pathological results: Pathological examination of benign nodules reveals normal thyroid tissue or benign hyperplasia; malignant nodules show cancer cells, abnormal cellular morphology, and infiltrative growth characteristics.

　　After detecting a category 4a nodule, it is important to follow medical advice for further examinations, such as fine needle aspiration biopsy, to determine its nature and promptly intervene if necessary. Regular follow-up and monitoring are essential to avoid delaying treatment.