Prognosis and Prognostic Factors for Distant Metastases and Tumor Mortality in Follicular Thyroid Carcinoma

Background: Distant metastases are more common in patients with follicular thyroid carcinoma (FTC) than in patients with papillary thyroid carcinoma, and the outcome is often poorer in patients with distant metastases. In this study, we attempted to identify the risk factors for distant metastases in FTC. Methods: Between 1989 and 1997, 134 patients with FTC underwent initial surgery, and their median follow-up period was 12.5 years. Seventeen patients had widely invasive FTC, and 117 had minimally invasive FTC. Distant metastases were observed in 36 patients (26.9%). Thirteen of these patients had distant metastases at the time of initial surgery (M1), and in the other 23 patients distant metastases were diagnosed with during their follow-up periods. Risk factors for distant metastases and cause-specific survival were analyzed. The factors analyzed were age at the time of initial surgery, sex, primary tumor size, histological findings (invasiveness, extent of vascular, and capsular invasion), and distant...