There is no such thing as “how soon will thyroid category 4a become malignant”, thyroid category 4a refers to thyroid nodules graded as TI-RADS 4a, with a certain degree of malignancy. 1. Thyroid nodules are a very common clinical lesion, according to the size, shape, border of the thyroid nodules in the ultrasound, artificially divided into 6 categories of thyroid nodules. 1 category for negative, 2 categories for the determination of benign nodules, 3 categories for possible benign nodules, 4 categories for suspected malignant nodules, 5 categories for the determination of malignant nodules, 6 categories for biopsy-proven malignant nodules. 2. Thyroid category 4 nodules are subdivided into 4a, 4b and 4c. Category 4a nodules represent patients with a 2%-10% likelihood of malignancy of the thyroid nodule; category 4b nodules have a malignancy likelihood of 10%-50%, and category 4c nodules have a malignancy likelihood of 50%-90%. However, the benign or malignant nature of the tumor needs to be further clarified by puncture biopsy. 3. For grade 4a thyroid nodules, further fine needle aspiration of the thyroid gland is recommended to clarify the diagnosis. If the test result is benign, regular and close review is recommended; if the test result is malignant, surgery for radical treatment of thyroid nodules is required. If grade 4a thyroid nodules are found, it is recommended to consult a doctor as soon as possible to clarify the nature of the nodules so as to avoid delaying the condition.