475. Follicular variant of papillary thyroid carcinoma: A comparative study on clinicopathologic features according to capsulation

Abstract

Background: The follicular variant of papillary thyroid carcinoma (FVPTC) is the most common histologic subtype of papillary thyroid carcinoma (PTC). But The follicular variant of papillary thyroid carcinoma (FVPTC) is difficult to diagnose due to pathologic features. There is also debate on the optimal extent of surgery. We separated FVPTC into two groups and compared the clinical features in an attempt to apply the treatment. Methods: All 121 patients with FVPTC who were diagnosed between 2003 and 2009 were reviewed and separated into two groups, an encapsulated group and an infiltrative group, based on whether a capsule was formed or infiltration occurred. These two different subtypes of FVPTC were compared on the traits of sensitivity of diagnosis and clinicopathologic features. Results: After review by a pathologist, 82 of 121 patients (67.8%) were found to have encapsulated tumors, and 39 patients (32.2%) had infiltrative tumors. There was no difference in age, sex, T stage, multicentricity. Patients with infiltrative FVPTC had a significantly higher rate of tumor size (p 1⁄4 0.004), lymph node metastasis (p < 0.001), lateral neck node metastasis(p < 0.001), TNM stage(p 1⁄4 0.004), lymphovascular invasion(p 1⁄4 0.029), thyroid capsular invasion (p < 0.001), and preoperative serum triiodothyronine (T3) level (p 1⁄4 0.025) compared with the encapsulated tumor group. There was no difference in FNA sensitivity and recurrence rate between the two groups. Conclusion: FVPTC can be separated into two subgroups by histologic features, and there are some clinicopathologic differences between the two groups. Patients who had infiltrative FVPTC had a higher rate of lymph node metastasis, lateral neck node metastasis, TNM stage, lymphovascular invasion, thyroid capsular invasion, and preoperative serum triiodothyronine (T3) level. It is suggested that the encapsulated group can be treated with limited surgery and the infiltrative group needs aggressive treatment. No conflict of interest.