Clinicopathologic predictors of thyroid bed recurrence of differentiated thyroid cancer using ultrasound-guided fine-needle aspiration biopsies

Background: Monitoring changes in the thyroid bed (TB) is one of the clinical mainstays for surveillance of recurrent thyroid carcinoma. Fine-needle aspiration (FNA) is a diagnostic tool that is commonly used to aid in the identification of residual or recurrent disease. The aim of our study was to evaluate the efficacy of ultrasound-guided FNA of the TB in detecting recurrent thyroid cancer and to correlate the findings with clinicopathologic parameters to identify predictors of TB recurrence. Methods: We retrieved cases of soft tissue masses within the TB that were evaluated for recurrence between January 1, 2006, and February 1, 2011. All ultrasound-guided FNA biopsies clinically suspected to indicate a lymph node metastasis and specimens with lymphocytes were excluded from the data. Results: Of the 291 patients identified for evaluation of recurrence, 250 had papillary thyroid carcinoma (PTC), 10 had follicular carcinoma, 22 had medullary carcinoma, 7 had Hürthle cell carcinoma, and 2 had a previous thyroidectomy for an unknown type of thyroid carcinoma. For all FNAs that were clinically suspicious or intermediate for recurrence, the rate of positivity was 71.8% (209 patients). All cases diagnosed as "positive for PTC" or "suspicious for PTC" on TB FNA were found to have soft tissue metastasis on follow-up surgical resection. This resulted in a negative predictive value of 88.4% and a positive predictive value of 100%. The average time between thyroidectomy and TB FNA was 73.5 months. Of the patients with a previous diagnosis of PTC, those with suspicious/positive cytology were more likely to be women, to be older at thyroidectomy, to have documented metastasis to other sites as well as extrathyroidal extension and multifocal primary disease as compared with nondiagnostic/negative cytology cases. Patient age ≥45 years, primary tumor size at thyroidectomy, and surgical resection margin status had no statistical significance for predicting risk of TB recurrence. Conclusion: TB recurrence of PTC is most likely to occur in patients who have the following clinicopathologic parameters: documented metastasis to any site, extrathyroidal extension, and increased number of primary cancer foci.