Clinical presentations and outcomes of surgical treatment of follicular variant of the papillary thyroid carcinomas

Background: The follicular variant of papillary thyroid carcinoma (FVPTC) presents with biological and morphological features similar to papillary thyroid carcinoma. Pre-operative diagnosis of FVPTC and its clinical course is important in identifying appropriate surgical procedures. Methods: This study enrolled 85 patients, 68 females (mean age 41.4 +/- 13.7 years) and 17 males (mean age 50.1 +/- 12.3 years) with papillary thyroid carcinomas diagnosed as FVPTC. From the patient database at Chang Gung Medical Center (CGMC), 170 pure papillary thyroid carcinoma cases and 85 with minimally invasive follicular thyroid carcinomas of gender- and age-matched patients were randomly selected as control groups. All patients were categorized into high- and low-risk groups according to AMES criteria. Results: Of the three groups, 7.1% (follicular), 11.8% (FVPTC) and 34.1% (pure papillary thyroid carcinoma) of patients presented with lymph node or soft tissue invasion (P = 0.0001). Additionally, 29.4, 11.8 and 2.4% of patients with follicular carcinoma, FVPTC and pure papillary thyroid carcinoma, respectively, presented with distant metastases at the time of diagnosis. Of the 85 FVPTC cases, 75 underwent pre-operative fine needle aspiration cytology (FNAC) examination at CGMC. Only 11 cases were diagnosed pre-operatively with papillary thyroid carcinomas. Kaplan-Meier survival curves for these three groups demonstrated that follicular thyroid carcinoma had a prognosis worse than both papillary thyroid carcinomas. Conclusions: Most FVPTC cases were diagnosed as follicular neoplasm via pre-operative FNAC. In this study, FVPTC patients had a high ratio of distant metastases, few lymph node metastases and soft tissue invasion. Aggressive treatment was indicated for the high-risk FVPTC patients.