ASO Visual Abstract: Encapsulated Angioinvasive Follicular Thyroid Carcinoma: Prognostic Impact of the Extent of Vascular Invasion

Background Previous studies have reported an association between four or more foci of vascular invasion (VI) and thyroid cancer prognosis, while the current study aimed to investigate the association between extent of VI and outcome of encapsulated angioinvasive follicular thyroid carcinoma (FTC). Methods The records of 264 patients with encapsulated angioinvasive FTC confirmed by surgical specimens at Ito Hospital from January 2005 to December 2014 were retrospectively reviewed. Thirteen patients had distant metastasis at diagnosis and were classified as M1. Results Among the 251 patients with M0 encapsulated angioinvasive FTC, the 10-year disease-free survival (DFS) rate was 84.1%. Those with a VI of 1 ( n = 116) or ≥ 2 ( n = 135) had a 10-year DFS rate of 94.5% and 75.4% ( p < 0.001), respectively, and those with a VI of 1–3 ( n = 180) or ≥ 4 ( n = 71) had a 10-year DFS rate of 84.8% and 82.1% ( p = 0.346), respectively. Multivariate analysis identified age ≥ 55 years ( p = 0.031) and VI ≥ 2 ( p = 0.002) as independent negative prognostic factors for DFS. Patients with M0 encapsulated angioinvasive FTC aged ≥ 55 years and VI ≥ 2 had significantly poorer prognosis and a 10-year DFS rate of 66.4% ( p < 0.001). Conclusions Patients with encapsulated angioinvasive FTC who had two or more foci of VI, especially patients aged ≥ 55 years, should be carefully followed-up.