Clinical behavior of follicular variant of papillary thyroid carcinoma: presentation and survival.

OBJECTIVE To determine the prevalence and extent of disease characteristics of the follicular variant of papillary thyroid carcinoma (FV-PTC) and the survival impact of this histopathological diagnosis compared to classical papillary thyroid carcinoma (C-PTC). STUDY DESIGN Cross-sectional population analysis of national cancer database. METHODS Cases of C-PTC and FV-PTC were extracted from the Surveillance, Epidemiology and End Results database for 1988-2006 and staged. Surgical extent and radioactive iodine (RAI) use were determined. Demographic and staging parameters were statistically compared according to tumor histology. Survival differences according to histology were determined with a Cox proportional hazards model, adjusting for age, sex, T-stage, N-stage, surgical therapy and RAI. RESULTS 46,699 patients were identified (68.4% C-PTC and 31.6% FV-PTC). Age at presentation and sex distribution were similar between FV-PTC (47.9 years; 79.3% female) and C-PTC patients (46.2 years; 77.3% female). Although nodal disease prevalence was significantly lower in FV-PTC compared to C-PTC (14.8% versus 27.8%, respectively, p<0.001), T-stage was not significantly different (p=0.450). Mean overall survivals for patients with FV-PTC (204.5 months) and C-PTC (205.3 months) were not significantly different (p=0.373). Cox regression analysis revealed that advanced age (p<0.001), male sex (p<0.001), advanced T-stage (p<0.001), and positive nodal disease (p<0.001) were associated with reduced overall survival, while histopathological subtype was not (p=0.360). CONCLUSION Disease presentation (with exception of nodal metastasis) and survival in patients with FV-PTC are statistically similar to that of C-PTC and accordingly these patients carry very similar prognoses.