Thick tumor capsule is a valuable risk factor for distant metastasis in follicular thyroid carcinoma

While the biological behavior of follicular thyroid carcinoma (FTC) has been studied in great detail using clinical experience, few studies have investigated pre- or intraoperative factors related to the risk of distant metastasis (DM) among patients with FTC. The aim of this study was to analyze the characteristics of FTC with DM.

This study retrospectively investigated 102 patients with FTC who underwent surgery between 1988 and 2013. We compared clinicopathological characteristics between FTC with and without DM.

Univariate analysis revealed nodal metastasis (p=0.045), serum thyroglobulin (Tg) at initial operation (≥1000ng/ml; p<0.0001), widely invasive appearance according to macroscopic findings (p<0.0001), thick tumor capsule (≥1mm; p<0.0001), vascular invasion (p=0.0003), extrathyroidal invasion (p=0.047), and venous tumor embolism (p=0.045) as significant risk factors for DM. Multivariate analysis conducted using pre- and intraoperative factors identified thick tumor capsule (≥1mm), serum Tg at initial operation (≥1000ng/ml), and macroscopically widely invasive appearance as risk factors independently associated with development of DM.

Patients with these risk factors should undergo total thyroidectomy and radioactive iodine ablation.