To evaluate the efficacy and the limitation of fine-needle aspiration (FNA) biopsy in thyroid bed lesions, a retrospective review was performed of the medical records of thyroid cancer patients who underwent ultrasound-guided FNA biopsy of the thyroid bed at The University of Texas MD Anderson Cancer Center over a 5-year period.
Data were reviewed on 220 FNA biopsies taken from thyroid bed lesions in 195 patients who had undergone thyroidectomy for thyroid carcinoma. Thyroid bed FNA results were compared with clinical follow-up, including neck dissection results.
Recurrent carcinoma was diagnosed by FNA biopsy in 139 of 220 (63%) cases. Neck dissections were performed for 112 sites identified by FNA biopsies, and recurrent carcinoma was confirmed in 110 sites. The concordance between positive and/or suspicious FNA diagnosis and positive neck dissection results was 98% (118 of 120 cases). A false-positive FNA occurred in one patient with follicular thyroid carcinoma. The other discrepancy was attributed to failure to remove the lesion by neck dissection. The diagnostic accuracy of thyroid bed FNA was 100% in papillary and medullary thyroid carcinoma and 93% in follicular thyroid carcinoma. Suspicious and rare false-negative FNA results were attributed to low cellularity and lack of characteristic cytomorphologic features of thyroid carcinoma.
Ultrasound-guided thyroid bed FNA biopsy is accurate and efficient in triaging patients who require post-thyroidectomy follow-up for recurrent thyroid carcinoma. Caution should be taken in the interpretation of FNA specimens that have low cellularity and lack characteristic cytologic features of thyroid carcinoma.