Thyroid Nodules with Indeterminate Cytological Category in Pediatric Age: Clinical and Surgical Management and Outcome in an Italian Multicentre Retrospective Study

Introduction: The rate of malignancy (ROM) among pediatric studies using the Bethesda System is 39.5% and 41.5% for atypia of undetermined significance/follicular lesion of undetermined significance and for suspected follicular neoplasm, respectively. Data reported on the basis of Bethesda System showed lower ROM in adults with indeterminate nodules (30.5% and 28.9%, respectively). Studies on adults based on the Italian Society of Anatomic Pathology and Cytology (SIAPEC) classification, report a ROM of 4-20.8% for TIR3a and 28-60.3% for TIR3b category, showing greater sensitivity in detecting malignancy. To date, very few performance data are available about SIAPEC classification in pediatric age. Methods: Multicentre retrospective data were collected from 44 pediatric subjects with thyroid nodules. Results: The distribution of cytological categories after fine-needle aspiration biopsy (FNAB) was 26 TIR3a and 18 TIR3b. Surgical approach was performed in 8/26 subjects with TIR3a and 18/18 subjects with TIR3b with a total ROM of 53.8% (12.5% for TIR3a, 72.8% for TIR3b). Total FNAB accuracy for the indeterminate cytologic category was 77%. Conclusion: The reported data seem to confirm a greater sensitivity of SIAPEC classification to identify malignancy within the indeterminate category also in pediatric age and not only in adulthood. This finding may orient clinicians toward clinical follow-up for the indeterminate TIR3a group and toward surgical approach with total thyroidectomy in the indeterminate TIR3b group, although this indication should be confirmed in further national multicenter studies including larger cohorts.