Follicular variant papillary thyroid carcinoma in a pediatric population.

Background: Follicular variant of papillary thyroid carcinoma (FVPTC) has been shown to be an intermediate entity between papillary (PTC) and follicular/Hurtle cell (FTC) thyroid carcinoma in adults. However, the tumor characteristics and prognosis of FVPTCs has not been studied in the pediatric population and is the focus of the current study

Methods: All pediatric patients ≤ 19 years of age with differentiated thyroid cancer (PTC, FVPTC, or FTC) were identified from the SEER registry from 1988-2009. Patients were divided into groups based on their histology. Adjusted odds ratios (ORs) for demographic, tumor, and treatment characteristics, as well as hazard ratios (HRs) for overall (OS) and disease-specific survival (DSS) were calculated for FVPTC.

Results: Of 1,956 patients, 445 (22.7%) had FVPTC. Compared to PTCs, FVPTCs were larger (OR: 2.03, CI:1.35-3.06), node negative (OR: 2.26, CI:1.61-3.19), occurred more often in patients < 15 years of age (OR: 1.58, CI:1.10-2.27), and had a partial thyroidectomy (OR: 1.61, CI:1.01-2.57). Conversely, compared to FTC, FVPTCs tumors were smaller (OR: 2.78, CI:1.70-4.53), node positive (OR: 5.26, CI:2.74-10.11), a first cancer (OR: 4.98, CI:2.48-9.99), and more often had a total thyroidectomy (OR: 2.84, CI:1.70-4.76). Only tumor size > 4 cm (HR: 13.92, CI:1.24-156.72) influenced OS for patients with FVPTC. There was no significant difference in OS or DSS between groups.

Conclusions: In pediatric patients ≤ 19 years of age, FVPTCs have intermediate tumor features compared to PTC and FTC, but a similar OS and DSS. All pediatric patients with thyroid cancer require lifelong surveillance. However, FVPTCs > 4 cm may warrant closer follow-up due to an increased risk of death.