Prognostic factors of minimally invasive follicular thyroid carcinoma: extensive vascular invasion significantly affects patient prognosis.

Follicular thyroid carcinoma (FTC) is divided into two categories: minimally and widely invasive FTC. Generally, the prognosis of minimally invasive FTC is excellent, but patients showing certain characteristics have a dire prognosis. In this study, we investigated the prognostic factors of minimally invasive FTC using a series of 292 patients. On multivariate analysis, extensive (4 or more) vascular invasion, age ≥ 45 years, and tumor size > 4 cm were independent prognostic factors of patient disease-free survival (DFS). Distant metastasis at diagnosis (M1) was the strongest prognostic factor of cause-specific survival (CSS). Extensive vascular invasion and tumor size > 4 cm also independently affected patient carcinoma death. Capsular invasion was not related to patient prognosis. The ten-year DFS rate of patients with extensive vascular invasion was 80%, which was poorer than that of those having tumor size > 4 cm (91%) and aged 45 years or older (90%). These findings suggest that 1) M1 most strongly affects the CSS of patients, and 2) M0 patients with extensive vascular invasion may be candidates for completion total thyroidectomy and radioactive iodine ablation.