[1113] Clinicopathologic Features and Long-Term Survival of Follicular Variant of Papillary Thyroid Carcinoma: A Comparison to Classical Papillary Thyroid Carcinoma

F Anatelli, A Ponce-Rodriguez, PW Grigsby, SK El-Mofty. Washington University, St Louis, MO; Dartmouth-Hitchcock Medical Center, Lebanon, NH; World Bank, Washington, DC

Background: Conflicting data exist in the literature regarding the clinical and pathologic differences between classical papillary thyroid carcinoma (CPTC) and the follicular variant of papillary thyroid carcinoma (FV). During a period of 25 years, 1,142 patients were diagnosed with papillary thyroid carcinoma at Barnes-Jewish Hospital, St. Louis, Missouri. Follow-up of these patients showed that patients who had FV had better progression-free and higher survival rates than those with CPTC. In this study, we compared the clinical and histopathologic features of the histologic variants in an attempt to correlate these features to the differences in patients' outcome.
Design: Of the original 1,142 papillary thyroid carcinoma cases, 294 were diagnosed as FV and 848 as CPTC. 142 FV cases had available microscopic sections, satisfied strict histopathologic criteria, and had complete medical records. We randomly selected 200 CPTC cases and used similar criteria to obtain a final sample of 118 cases. 109/142 (76.7%) of the FV and 88/118 (74.5%) CPTC patients were female. 45.0% of the FV and 40.6% CPTC patients were 45 years of age or older. All 260 patients in both groups had been treated with total thyroidectomy and post operative I-131.
Results: Using the Chi Square, Kaplan-Meier survival with long-rank (Wilcoxon) test of equivalance, we found that patients with FV have better progression-free (p=0.0037) and higher survival rates (p=0.035) than patients with CPTC. Patients with CPTC presented with a higher T stage (p<0.0001), more common lymph node metastasis (p<0.0001), and more advanced overall TNM stage (p<0.005). Microscopically, CPTCs were more likely to show extrathyroidal extension than FV (p<0.0001). There were no statistical differences between CPTC and FV with regards to patients' age, gender, the tumor's vascular invasion, multifocality or the presence of lymphocytic thyroiditis.
Conclusions: Follicular variant of papillary thyroid carcinoma has a more favorable long-term prognosis than classic papillary thyroid carcinoma. This difference is associated with earlier T stage less extrathyroidal extension and lymph node metastasis, as well as a lower overall TNM stage, at presentation. While FV may be a distinct phenotypic and molecular disease entity, our findings suggest that FV may also be an earlier form or a precursor of CPTC.
Category: Head & Neck

Monday, March 9, 2009 1:00 PM

Poster Session II # 183, Monday Afternoon