Preoperative diagnosis of thyroid cancer by FNAB has a sensitivity of 83, a specificity of 92, a positive predictive rate of 75, a false negative rate of 5, and a false positive rate of 5. FNAB cannot distinguish follicular carcinoma of the thyroid from follicular cell adenoma. Preoperative FNAB can help reduce unnecessary thyroid nodule surgery and help determine the appropriate surgical plan. FNAB can be considered for any thyroid nodule >1 cm in diameter. However, FNAB is not routinely performed in the following cases: 1) hot nodules with autonomic uptake confirmed by thyroid nuclide imaging; 2) nodules that are purely cystic on ultrasound; 3) nodules that are highly suspected of being malignant on ultrasound imaging. FNAB is not recommended for thyroid nodules <1 cm in diameter, but ultrasound-guided FNAB may be considered if the following conditions exist: 1) ultrasound suggests malignant nodules; 2) ultrasound images of cervical lymph nodes are abnormal; 3) history of radiation exposure to the neck or radiation contamination in childhood; 4) family history of thyroid cancer or thyroid cancer syndrome; positive PET images; 5) abnormally elevated serum Ct levels. Abnormally elevated serum Ct level.