Predictive Factors of Malignancy in Thyroid Nodules with a Cytological Diagnosis of Follicular Neoplasm

In cases of follicular neoplasm identified by thyroid fine-needle aspiration (FNA), surgery is required to achieve a precise diagnosis. We investigated potential clinical factors for the preoperative prediction of malignancy in thyroid nodules with a cytological diagnosis of follicular neoplasm. We retrospectively reviewed the data of 97 patients who were diagnosed with follicular neoplasm by FNA and had undergone surgery at the Korea Cancer Center Hospital between April 2010 and April 2012. Age, sex, laboratory data (such as thyroid-stimulating hormone, free T4, thyroglobulin (Tg), and Tg antibody), and ultrasonographic findings were reviewed from the electronic medical records. Of 97 patients, 50 (51.5 %) were diagnosed with benign nodules, 16 (16.5 %) with follicular thyroid carcinoma (FTC), and 31 (32.0 %) with papillary thyroid carcinoma (PTC). In comparison with the features of benign nodules, FTC presented with a large nodule size, high serum Tg level, isoechogenicity, calcifications, and peripheral halo, whereas PTC exhibited traits similar to those of benign nodules, except for high serum Tg level and the presence of calcifications on ultrasonography. Therefore, a high serum Tg level (≥75 ng/mL) and calcification were the only significant predictive factors for malignancy in case of follicular neoplasm (p < 0.01). Serum Tg levels and the presence of calcification on ultrasonography are important clinical features to predict malignancy in thyroid nodules with cytological diagnosis of follicular neoplasm.