The value of ultrasound-guided fine-needle aspiration biopsy (FNAB) and frozen section examination (FS) in the diagnosis of thyroid cancer.

Background and aims: Although only a small minority of thyroid nodules are malignant, a large proportion of operations are performed to exclude malignancy. The purpose of this study was to evaluate the role of preoperative ultrasound-guided fine-needle aspiration biopsy (FNAB) and intraoperative frozen section examination (FS) in the management of thyroid cancer.

Material and methods: A retrospective study of 664 consecutive patients operated on for thyroid cancer from 1966 through 1994 at the Meilahti Hospital was performed. FNAB was taken with manual guidance in the sixties and seventies and with ultrasound guidance in the eighties and nineties. FS was performed in 335 cases. Malignancy was not known preoperatively in 210 cases.

Results: Ultrasound-guided FNAB was more accurate than manually guided FNAB (75 out of 143 or 52.4% vs. 112 out of 276 or 40.6%) in detecting malignancy in spite of the fact that the tumors were smaller (23 +/- 15 mm vs. 30 +/- 22 mm, p = 0.011). A true positive FS diagnosis was given in 250 out of 335 (74.6%) of patients. However, in follicular carcinoma, the amount of true positive FS diagnoses was only 12 out of 27 (44.4%).

Conclusions: Ultrasound guidance has improved the sensitivity of FNAB. Follicular neoplasia is a problem for both FNAB and FS.