Occult Thyroid Cancer in Autoimmune Thyroiditis: Lymph Node Ultrasound as the Sole Diagnostic Indicator of Malignancy in a Pediatric Case of Papillary Thyroid Carcinoma

Background: Autoimmune thyroiditis (AIT) is a common thyroid disorder in children, linked to an increased risk of papillary thyroid carcinoma (PTC). AIT's characteristic ultraso-nographic features can obscure PTC, delaying diagnosis. Case Presentation: An 11-year-old girl with a two-year history of AIT presented with persistently elevated thyroid-stimulating hormone (TSH) levels despite levothyroxine therapy. Examination revealed a firm, slightly enlarged right thyroid lobe. Serial thyroid ultrasounds showed typical AIT features, with no apparent tumor. However, cervical lymph node ultrasound detected a suspicious lymph node with pathological vascularization. Fine-needle aspiration suggested possible PTC metastasis. The patient underwent total thyroidectomy with central and right lateral neck dissection. Histopathology confirmed mul-tifocal PTC with cervical lymph node metastases (pT3aN1bM0). Postoperative radioactive iodine therapy resulted in undetectable thyroglobulin levels, indicating biochemical response. Conclusion: Children with AIT may harbor occult PTC even without thyroid gland abnormalities suggestive of malignancy. Comprehensive ultrasound evaluation, including cervical lymph nodes, is vital for early detection and timely treatment.