pT1a Papillary Thyroid Carcinomas in Pediatric Patients.

Background: Observational studies in adults suggest that incidental PTC (iPTC) and non-incidental PTC (niPTC) are distinct entities. We examine the incidence of iPTC in pediatric patients undergoing thyroidectomy for benign conditions and compare clinical and histopathologic findings, as well as outcomes, of iPTC with those of niPTC.

Methods: A retrospective chart review was conducted at the Children's Hospital of Philadelphia between August 2010 and February 2023 to identify pediatric patients who underwent thyroidectomy and were diagnosed with pT1a PTC.

Results: iPTC was identified in 23 of 453 (5.1%) patients undergoing thyroidectomy for benign conditions. Within a cohort of 66 patients diagnosed with pT1a PTC, 23 (34.8%) were classified as iPTC, and 43 (65.2%) were classified as niPTC. Compared to niPTC, iPTC had a significantly smaller median greatest dimension (iPTC: 3 mm, niPTC: 7 mm, p < 0.001), a lower rate of lymphatic invasion (iPTC: 0%, niPTC: 60.5%, p < 0.001), and AJCC N1 disease (iPTC: 0%, niPTC: 55.8%, p < 0.001). Most iPTC (22 out of 23 [95.7%]) were classified as ATA pediatric low-risk, while 6 out of 43 (14.0%) niPTC were categorized as intermediate/high-risk. Patients with iPTC and niPTC were followed for a median of 3.3 and 5.7 years, respectively. There was no evidence of persistent or recurrent disease in any patient with iPTC during this time frame.

Conclusions: iPTC may be found in 5.1% of pediatric patients undergoing thyroidectomy for benign conditions. Similar to adults, iPTC in pediatric patients appears to be indolent with a minimal risk for invasive features and a low risk for persistent or recurrent disease. In contrast to iPTC, niPTC exhibits the potential for invasive behavior and should be regarded as a distinct entity.