Follicular and Hürthle cell carcinoma: predicting outcome and directing therapy

Follicular thyroid cancer is a heterogeneous disease including follicular and Hürthle cell and tumors with and without vascular and major capsular invasion. Analyses of prognosis and risk groups have been criticized for not taking these differences into account.

Retrospective analysis was done of 240 patients treated from 1940 to 1997.

Ninety-two patients without vascular or major capsular invasion followed up for a median of 14 years had no recurrences or deaths. In the remaining 148 patients, 32 had Hürthle cell and 116 had follicular cell carcinoma. Patients with Hürthle cell carcinoma were significantly older (55 vs 47 years; P = .0014). Lymphatic metastases did not influence outcome. Patients who were at high risk by age and sex, metastases, extent, and size had a 20-year survival rate of 36% for follicular and 35% for Hürthle cell carcinoma; patients at low risk had 20-year survival rates of 94% and 89%, respectively, with no significant difference between follicular and Hürthle cell carcinoma. Recurrences were treated successfully in 33% of patients with follicular carcinoma but never cured in patients with Hürthle cell carcinoma. Bilateral versus unilateral operation or radioiodine for ablation did not alter outcome.

Follicular and Hürthle cell carcinoma with minimal capsular invasion behaved benignly. Age and sex, metastases, extent, and size risk criteria differentiate strongly between patients with high-risk and low-risk follicular and Hürthle cell carcinoma. Controlling for risk factors, Hürthle cell and follicular cell carcinomas have similar prognoses.