Background. Hu ¨rthle cell carcinoma of the thyroid is a variant of follicular carcinoma, which has been considered by many as a more aggressive disease than the usual welldifferentiated carcinoma of the thyroid. Others, however, have found Hu ¨rthle cell carcinoma to be a low-grade malignancy with little morbidity or mortality.
Methods. This is a retrospective report on all patients with Hu ¨rthle cell carcinoma diagnosed during the years 1951-1997 by the authors. The behavior of the disease and results of treatment were analyzed biostatistically and the outcome was compared with that of patients with pure follicular carcinoma treated during the same period.
Results. Forty-two patients were diagnosed with Hu ¨rthle cell carcinoma and 153 with follicular carcinoma during this period (2.8% and 10.3% of all differentiated carcinomas of the thyroid, respectively). The rate of local recurrence and disease-related mortality were both 9.5%, compared with 3.2% & 15.7%, respectively, for the follicular cancers. There was a trend for better outcome in patients younger than 55 years of age, in patients with tumors under 4 cm in size, and in patients treated by total thyroidectomy. Distant metastases occurred in four patients (9.5%) and were the cause of disease-related mortality in three.
Conclusions. When treated assertively, Hu ¨rthle cell carci-noma of the thyroid, an oncocytic variant of follicular carcinoma, has a favorable outcome, similar to that of pure follicular carcinoma. Uniting those two entities in a future classification and reporting should be considered.