Follicular thyroid cancer in children and adolescents: clinicopathologic features, long-term survival, and risk factors for recurrence.

Children and adolescents represent 1-1.5% of all patients with thyroid cancer (TC). The vast majority of TC in children and adolescents is papillary TC; follicular TC (FTC) is exceedingly rare. In this study, we evaluate the clinical and pathological features of FTC in children and adolescents. We also report the risk factors for post-operative tumor recurrence and the associated outcomes. Twenty children and adolescents (under 21 years old) with FTC have been treated and followed at Noguchi Thyroid Clinic and Hospital Foundation since 1946. All patients underwent surgery (lobectomy, 11; subtotal thyroidectomy, 8; and total thyroidectomy, 1), and 8 patients received postoperative external beam radiation therapy. The incidence of FTC in children and adolescents was 1.9% among all FTC patients treated in our hospital. Histopathology revealed vascular and capsular invasion in 9 and 20 patients, respectively. The tumor recurrence rate in FTC with vascular invasion is significantly higher than in those without it (p = 0.038). No other factors were significant. Patients with recurrences were treated with completion thyroidectomy and ¹³¹I radioactive iodine therapy. There were no significant differences in the rates of disease-free survival or cause-specific survival when pediatric/adolescent FTC patients were compared to adults with FTC. FTC is very rare among children and adolescents, but the outcomes are similar to those observed among adults. Vascular invasion is poor prognostic indicator in pediatric/adolescent FTC patients.