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

Abstract

Background: Autoimmune thyroiditis (AIT) is a common thyroid disorder in children, linked to an increased risk of papillary thyroid carcinoma (PTC). Characteristic ultrasonographic features of AIT 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, a 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 multifocal PTC with cervical lymph node metastases (pT3aN1bM0). Postoperative radioactive iodine therapy resulted in undetectable thyroglobulin levels, indicating a biochemical response. Conclusions: 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.