BACKGROUND

Thyroid microcarcinomas (TMCs) are increasing in the general population, most commonly in older individuals; however, the incidence, characteristics, and outcomes of TMCs in pediatric patients has not been studied.

METHODS

All patients ≤19 years of age with differentiated thyroid carcinoma (DTC) were identified from the surveillance, epidemiology, and end results registry from 1988 to 2009. Patients were divided into two groups based on tumor siz e: TMCs (≤1 cm) and tumors >1 cm. Demographic, tumor, and treatment characteristics, as well as overall survival (OS) and disease-specific survival (DSS), were compared between the two groups. The TMC group was analyzed separately for predictors of overall and disease-specific death.

RESULTS

Of 1825 pediatric DTC patients, 8.4 % had a TMC, and, over the past decade, the incidence has decreased (6.5 vs 14.5 %; p < 0.001). Compared to patients with DTCs >1 cm, TMCs were more likely to have papillary histology, negative lymph nodes, be treated with a partial thyroidectomy [odds ratio (OR) 3.46, CI 2.02-5.93] and not receive radioiodine (OR 1.77, CI 1.10-2.83). Neither OS (TMC: 253.59 months; DTC >1 cm: 257.97 months) nor DSS (TMC: 256.38 months; DTC >1 cm: 260.77 months) differed between groups. Predictors of decreased OS in the entire cohort included secondary malignancy status (p = 0.001), black race (p = 0.006) and follicular or Hurthle histology (p = 0.001). In patients with primary TMC, only follicular or Hurthle histology (p = 0.001) predicted decreased OS.

CONCLUSIONS

TMCs in patients ≤19 years of age are declining and comprise <10 % of pediatric thyroid malignancies. TMCs are most commonly treated with a partial thyroidectomy not followed by radioiodine, and have an excellent OS and DSS.