Prognosis and prognostic factors of follicular carcinoma in Japan: Importance of postoperative pathological examination

Background Follicular carcinoma is known to show a worse prognosis than papillary carcinoma because of distant metastasis in higher incidence. However, few studies have been published regarding the prognosis of follicular carcinoma patients in Japan, which prompted us to investigate this issue. Methods We examined the prognosis and whether and how various clinicopathological features have affected disease-free survival (DFS) and cause-specific survival (CSS) of 334 patients who underwent initial surgery for follicular carcinoma. Results In 18 patients (5.4%), curative surgery could not be achieved because of distant metastasis at surgery in 17 patients and local extension in 1 patient. For 316 patients who underwent curative surgery, 5-year and 10-year DFS rates were 88.4% and 75.3%, respectively. Poorly differentiated carcinoma and widely invasive carcinoma, together with some conventional prognostic factors, predicted poorer DFS of patients. On multivariate analysis, poorly differentiated carcinoma was an independent prognostic factor for DFS. The 5-year and 10-year CSS rates for these 334 patients were 96.4% and 90.4%, respectively. Curative surgery and poorly differentiated carcinoma were recognized as independent prognostic factors. Conclusions We can hypothesize that follicular carcinoma in Japan is generally a nonaggressive disease with a good prognosis. However, because poorly differentiated or widely invasive carcinomas showed a worse prognosis, postoperative pathological examination is important in predicting patient prognosis.