Thyroid nodule 4a, is the ultrasound grade for thyroid nodules. A thyroid nodule color ultrasound grading of 4 or higher is likely to be a malignant thyroid nodule, which is thyroid cancer. So, a thyroid nodule 4a is likely to be thyroid cancer, and the likelihood of it being thyroid cancer is about 30%. For thyroid nodules that are considered to be thyroid cancer, surgery is generally recommended, with part of the thyroid gland surgically removed. Depending on the postoperative pathology, if it is thyroid cancer, lifelong treatment with eugenol can be taken after surgery to inhibit tumor recurrence and metastasis. Some patients are unwilling to undergo surgical treatment. For patients with thyroid 4a, thyroid ultrasound can be rechecked regularly, usually once every 3 months. If the level continues to rise and becomes 4b or 4c, surgical treatment is recommended.