Clinicopathological Findings of 220 Pediatric, Adolescent, and Young Adult Patients with Thyroid Cancer in Fukushima Medical University Hospital

<b><i>Background:</i></b> Thyroid ultrasound examinations (TUEs), conducted as part of the Fukushima Health Management Survey (FHMS), were initiated to monitor the health status of residents after the Fukushima Daiichi Nuclear Power Plant accident owing to concerns regarding the increased incidence of thyroid cancer among children, as observed after the Chernobyl Nuclear Power Plant accident. This study reported the clinicopathological characteristics of patients with thyroid cancer diagnosed through the FHMS and treated at the Fukushima Medical University Hospital. <b><i>Methods:</i></b> Data regarding the clinicopathological characteristics of patients with thyroid cancer were collected and evaluated in this descriptive study. <b><i>Results:</i></b> Among the 263 patients diagnosed with thyroid cancer as of September 2021, 220 patients with cytologically diagnosed thyroid cancer were treated as referrals from the FHMS. The median (interquartile range) age at the time of diagnosis was 18.6 (16.2-20.3) years. The median maximum tumor diameter was 13.0 (10.4-18.0) mm. To reduce surgical invasiveness, 199 patients (90.1%) underwent unilateral lobectomy. Pathological findings were suggestive of papillary thyroid carcinomas (PTC) in 216 (98.2%) patients; among them, 205 patients had PTC of the classical type. In addition, 216 (98.2%) patients had stage I disease. Cancer cell extension in the sternothyroid muscle or perithyroidal soft tissues and microscopic lymphovascular invasion were observed in 112 (50.9%) and 123 (55.9%) patients, respectively. No differences were observed between the two age groups (<18.6 years and ≥18.6 years) in terms of the clinical or pathological characteristics of thyroid cancer: risk classification (<i>p</i> = 0.69) and American Thyroid Association pediatric risk level (<i>p</i> = 0.24). Compared with those from previous reports, few surgical complications were observed. <b><i>Conclusions:</i></b> Patients with thyroid cancer diagnosed with TUEs underwent safe and minimally invasive operations, and careful postoperative follow-up was provided. The pathological findings of the detected thyroid cancers indicated that the majority were classical papillary carcinomas, and approximately half of the patients had extrathyroidal or lymphovascular invasion. No differences were observed between the two age groups in terms of the clinical or pathological characteristics of thyroid cancer.