Follicular Thyroid Carcinoma: Clinicopathologic Features, Prognostic Factors, and Treatment Strategy

ABSTRACT

PURPOSE: Follicular thyroid carcinoma (FTC) is a relatively rare form of thyroid carcinoma that often presents at a more advanced stage of disease with a higher incidence of distant metastases because of its propensity for vascular invasion. However, FTC and papillary thyroid carcinoma (PTC) have similar prognoses when they are matched for age and stage. Therefore, this study was conducted to evaluate the useful prognostic factors and determine the optimal management of FTC. METHODS: This study was conducted on 216 patients with FTC who underwent thyroidectomy at our institutions between April 1986 and August 2006. The patients included 174 women and 42 men with a mean age of 41 (4~87) years, and patients underwent follow-up evaluation for a mean period of 114 (6~253) months. The potential risk factors for treatment outcome were calculated using multivariate analysis, and the prognostic accuracy of UICC/AJCC pTNM staging, AMES, AGES, MACIS, and Degroot classification for predicting survival were compared. RESULTS: During the follow-up period, 13 (6.0%) patients developed locoregional recurrences and 8 patients (3.7%) showed distant metastases. In addition, cause specific mortality was seen in 8 patients (3.7%). The overall survival and cause-specific survival (CSS) rates at 10 years were 95.4% and 89.3%, respectively, and these cases were accurately predicted by the AMES and pTNM staging systems. The Cox proportional hazards revealed that gender (P=0.015), angioinvasion (P=0.013), invasion to adjacent structure (P=0.003), widely invasive carcinoma (P=0.028), and distant metastases at the time of presentation (P<0.001) were independent prognostic factors for survival. CONCLUSION: The extent of surgery in cases of FTC should be individualized based on the clinicopathologic findings; Conservative surgery should be adequate for cases of minimally invasive FTC without angioinvasion, however total or near-total thyroidectomy should be conducted in cases of widely invasive and minimally invasive FTC with angioinvasion.