Follicular thyroid carcinoma: differences in clinical relevance between minimally invasive and widely invasive tumors.

Background: Evidence on the biological behavior and clinical courses of minimally invasive and widely invasive follicular thyroid carcinoma (MI-FTC, WI-FTC) is still debatable. The current study was conducted to identify differences between MI and WI tumors and those prognostic parameters influencing late outcome such as local recurrence and survival.

Methods: From January 1998 to October 2013, 71 patients were operated on in our department because of a FTC. A retrospective cohort study was carried out to compare 42 MI-FTC and 29 WI-FTC. The comparison involved evaluation of patient characteristics, tumor characteristics, tumor staging, and risk assessment.

Results: A diameter greater than 4.0 cm, the presence of vascular invasion, the TNM stage III-IVA, and the high risk at AMES system risk stratification were independent factors significantly related to the presence of a WI-FTC. The only independent predictor of recurrence and disease-free survival at 10-year follow-up was a tumor size greater than 4.0 cm.

Conclusions: More attention must be paid in the postoperative tumor re-staging of those patients with tumor size larger than 4.0 cm, which was the only parameter predicting recurrence and influencing disease-free survival. Nevertheless, definitive recommendations cannot be made without a longer follow-up.