Fine-needle aspiration cytology (FNA) and Frozen section biopsy (FS) have been used to distinguish benign lesions from malignancies and for deciding the extent of operative procedures to be used in the management of thyroid nodules. We performed this study in order to determine the diagnostic value of FNA, the need for FS in intraoperative procedures, and their value in deciding the extent of surgery.

The medical records of 365 consecutive patients who had undergone surgery for thyroid nodules at the Department of Surgery, Hanyang University Hospital, between Jan. 1996 and Dec. 1998 were reviewed retrospectively. Both FNA and FS were performed on all patients who underwent thyroid surgery during this period. Among these, 35 patients who were diagnosed as insufficient for diagnosis by FNA were excluded.

Definitive histopathological diagnosis revealed benign lesions in 232 patients and malignancies in 98. A borderline group consisted of patients whose specimens were interpreted as follicular neoplasms by FNA and FS. The overall results for FNA and FS were as follows: sensitivity, 98 versus 100; specificity 97 versus 99; and diagnostic accuracy, 97 versus 99%. Five patients who were diagnosed with benign lesions by FNA were rediagnosed by FS as having malignant lesions. The final diagnosis was papillary carcinoma. Of the 45 patients who were interpreted borderline by FNA, 7 patients had benign lesions and 38 were borderline by FS. Finally, 34 patients were diagnosed as having benign lesions and 11 as having malignancies.

FNA has a high diagnostic accuracy for the differential diagnosis of thyroid nodules. FS may be unnecessary for patients whose FNA results indicate malignancy, particularly in cases of papillary carcinoma, therefore the routine use of FS for patients who have been diagnosed as having a papillary carcinoma by FNA may be omitted. If FNA results are borderline, FS may be helpful in confirming a follicular neoplasm. If FNA indicates a benign status, FS seems to be necessary to decide the extent of surgery.