Prognosis of differentiated thyroid carcinoma in pediatric patients

INTRODUCTION: In the pediatric age, thyroid carcinoma (TC) is the most common endocrine tumour, even if rare. The incidence has increased in recent decades, due to both the increased use of ultrasound and a possible real increase linked to environmental factors. Compared to adults, it presents with more aggressive features. Nevertheless, the prognosis remains excellent, maybe because of the aggressive treatment patients undergo. However, the best treatment for these patients has not yet been defined, as a balance must be struck between the radicality of treatment and the risk of overtreatment. In this retrospective study, we describe the paediatric population affected by thyroid cancer in a third-level endocrinological centre. MATERIALS AND METHODS: Patients ≤ 18 years old diagnosed with TC referred to the Endocrinology Unit of the AOU of Modena (1976-2024) were retrospectively evaluated. We considered subjects for whom we had data on demographics, risk factors, surgery, complications, radioiodine therapy (RAIT), histology, TNM, biohumoral, and radiological follow-up. The outcome was defined according to the American Thyroid Association guidelines (ATA). RESULTS: Diagnoses have been increasing since 2000, with a peak after 2010. None of the 17 patients (15 F, 2 M), median age 15 years (min 12, max 18), had any known risk factors for TC. All the patients underwent total thyroidectomy, with concomitant central compartment lymphadenectomy in 56.25% of cases, lateral in 25%. Among histotypes, classic papillary carcinoma prevailed (61.5%). Only one patient had an aggressive variant (solid trabecular). The median size was 19 mm (min 5, max 70 mm). 21.4% had multifocality, 77.8% had minimal extrathyroidal extension, and 25% had vascular invasion. According to the 8th TNM edition, 46.15% were classified as T1, 30.8% as T2, and 23.1% as T3. Regarding the nodal involvement, 69.2% were N1, and only one patient was classified as M1 with iodocaptant lung metastases. About 90% received treatment with RAI for ablative purposes, with only one patient requiring multiple treatments. Permanent hypoparathyroidism was the only post-operative complication, affecting 35% of the patients. There was a slight decrease in the use of the RAIT and prophylactic lymphadenectomy in recent years. After a median follow-up of 68 months (min 4, max 557), 88.2% of patients had an excellent response to treatment, while 11.8% presented an incomplete biochemical response. CONCLUSIONS: The incidence of pediatric TC is steadily increasing, especially in recent decades, although it remains rare. It affects mainly adolescent females. Risk factors, such as familiarity and previous radiation exposure, do not seem to play a significant role. Fortunately, differentiated histotypes prevail, with an excellent prognosis. TC presents with greater size and extension at onset if compared to adults. Treatment is more aggressive than in adults, resulting in an increased incidence of hypoparathyroidism. However, the large observation period and pre-2000 surgical techniques influence these data. Larger case series are needed to understand the best possible treatment with the least number of complications impacting long-term health and quality of life.