Diagnostic utility of fine needle aspiration cytology in pediatric thyroid nodules based on Bethesda Classification.

OBJECTIVES: The Bethesda system for reporting cytopathology (TBSRTC) has been widely adopted in the management of thyroid nodules. Based on the limited pediatric data available, the implied malignancy risk for each of the categories may be significantly different in pediatrics vs. adults, especially in the indeterminate categories (Bethesda Class III or IV). We report the diagnostic utility of fine needle aspiration (FNA) biopsy at our institution based on the Bethesda system and the risk of malignancy in each category. METHODS: We retrospectively reviewed all patients who underwent a thyroid FNA at our tertiary pediatric hospital from 12/1/2002 to 11/30/2018. FNA results were classified according to TBSRTC. Patient demographics, cytology, histopathology, radiological and clinical follow-ups were examined. RESULTS: A total of 171 patients were included with 203 cytological samples. Average age at initial FNA was 14.7 years (range 6.9-18.6 years). The numbers of nodules reported for Bethesda categories I-VI were 29, 106, 22, 14, 6 and 26, respectively, and the rate of malignancy was: 13.8, 4.7, 22.7, 35.7, 83.3 and 100%, respectively. Use of ultrasound guidance reduced the non-diagnostic rate from 38.1 to 11.5%. Introduction of on-site adequacy testing further reduced the non-diagnostic rate to 6.5% since 2014. CONCLUSIONS: The risk of malignancy for thyroid nodules in this pediatric cohort is higher than reported in adults. However, rates described here are much closer to adult ranges than previously published pediatric cohorts. The addition of adequacy testing improved the non-diagnostic rate of FNA procedures performed with ultrasound guidance.