Follicular Variant of Papillary Thyroid Carcinoma

HYPOTHESIS: The clinical behavior of the follicular variant of papillary thyroid carcinoma (FVPTC) is similar to pure papillary thyroid carcinoma (PPTC) and completely different from follicular thyroid carcinoma (FTC). DESIGN: Retrospective analysis of prospectively documented data. SETTING: Referral center of a university hospital. PATIENTS: Two hundred thirty-seven consecutive patients with follicular cell-derived thyroid carcinomas were operated on in our institution during a 15-year period, from January 1, 1980, to December 31, 1994. Of the 154 PTC patients, 37 (24%) had FVPTC. The mean follow-up was 128.2 months (10.7 years). MAIN OUTCOME MEASURES: Demographic features, tumor characteristics, local and distant spread, persistence or recurrence of disease, and carcinoma-related mortality were compared between the groups with FVPTC, PPTC, and non-Hürthle cell FTC (NHFTC). RESULTS: The frequency of multicentricity was significantly higher in the FVPTC group than in the PPTC group (P =.03) or in the NHFTC group (P =.01) (12 32% of 37 patients vs 17 15% of 117 patients vs 6 10% of 58 patients, respectively). The incidence of cervical lymph node metastases was lower in the FVPTC group than in the PPTC group (P =.30) and higher than in NHFTC group (P =.004) (12 32% of 37 patients vs 53 45% of 117 patients vs 6 10% of 58 patients, respectively). At diagnosis, no patient with FVPTC showed distant metastases, compared with 5 patients (4%) with PPTC (P =.34) and 19 (33%) with NHFTC (P<.001). There was no carcinoma-related death in the FVPTC group. The strikingly poorer prognosis for the NHFTC group was statistically significant (P<.001), whereas the difference in carcinoma-specific survival between the PPTC and the FVPTC groups did show a trend toward better survival in the FVPTC group. CONCLUSION: The clinical behavior of the FVPTC group did not differ significantly from that of the PPTC group, whereas compared with the NHFTC group, the FVPTC group showed statistically significant differences for most of the analyzed variables.