Morbidity and mortality in follicular thyroid cancer.

The natural history and results of treatment have been analyzed in a group of 49 patients with follicular thyroid carcinoma who were followed for an average of 10.7 yr. Striking differences between the course of follicular thyroid carcinoma and the course of papillary carcinoma are evident. Deaths from cancer were double (16% for follicular), age at diagnosis was older, and age at death was younger. All deaths and recurrences happened within 13 yr, in contrast to the continued experience of deaths and recurrences in papillary cancer, even through 40 yr of observation. Adverse outcome correlated with extent of disease at diagnosis and with size of primary tumor, but did not correlate with vessel invasion, extent of capsule invasion, degree of dedifferentiation, extent of primary surgery, or radioactive iodide ablation. These observations are again in striking contrast to experience with papillary cancer. No patient with intrathyroidal disease who was under age 45 at diagnosis and with a primary tumor of less than 2.5 cm died. Our observations suggest that follicular cancer, even if apparently intrathyroidal, carries a high mortality rate in patients over age 45 or in those with tumors larger than 2.5 cm at the time of diagnosis and suggest that we must consider additional therapeutic measures in this group of patients, including larger radioiodine doses for initial therapy, external radiotherapy, and even possibly prophylactic chemotherapy.