The clinical significance of atypia in thyroid fine-needle aspiration

Fine-needle aspiration cytology (FNAC) of thyroid nodules has become the primary diagnostic tool in the evaluation of thyroid nodules. However, the diagnostic utility of thyroid cytology may be limited by the presence of atypical cytologic patterns. In patients with atypical cytology in FNAC, treatment concept is not established. The purpose of this study is to correlate subcategories of atypical cytology of thyroid gland with final histologic diagnoses, and to help develop a treatment plan for thyroid nodules. We retrospectively reviewed 133 specimens of patients with atypical cytology of thyroid nodule according to preoperative FNAC. The atypical cytologic patterns were classified and divided into three groups: follicular neoplasm with nuclear atypia (FNA), nodular hyperplasia with nuclear atypia (NHA), possible papillary carcinoma (PP). Then we investigated the malignancy rates of each group. Among the 133 specimens with atypical cytology, 43 cases (32.3%) were proved to be malignant. Of the 97 cases in the FNA group, 29.9% were malignant. In the NHA and PP groups, 23.1 and 47.8% were malignant, respectively. However, there was no statistical significance in the incidence of malignancy among the three groups. There was also no statistical difference among all groups, with regard to lymph node metastasis and recurrence. In conclusion, if aspirates manifest atypical cytologic pattern, surgery should be considered, especially if the results are categorized as PP. Intraoperative frozen section should be confirmed and the extent of resection should be determined by final pathology.