A Pediatric Patient With Papillary Thyroid Carcinoma With Local and Distant Metastases

Introduction: Thyroid cancer is less common among children than adults, but the incidence has been increasing, especially in adolescents. Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer in pediatric patients representing more than 90% of all cases. Children with PTC are likely to present with regional lymph node metastases, but distant metastases are rare. We present a 12-year-old female patient who presented with a neck mass found to be PTC with neck and pulmonary metastases. Case Presentation: A 12-year-old girl previously healthy presented to her primary doctor with a neck mass for several months. The patient had no other complaints, and the physical exam was notable for a palpable right anterior neck mass measuring 3x4cm. Thyroid studies were remarkable for a thyroid-stimulating hormone (TSH) of 2.13 uIU/mL (0.350-4.94) and negative antithyroid antibodies. Initial neck ultrasound (US) showed a multilobulated right thyroid nodule with macrocalcifications. Fine needle aspiration (FNA) of the nodule revealed PTC. Patient underwent neck and chest computed tomography (CT) preoperatively, notable for cervical lymph nodes involvement and multiple bilateral lung nodes less than 1cm each. She underwent neck exploration and total thyroidectomy and was started on thyroid hormone replacement therapy afterwards. Pathology of the specimen revealed PTC with extension into the perithyroidal soft tissue and two out of five lymph nodes with metastatic PTC. She underwent I-123 whole-body scan (WBS) eight weeks later, followed by I-131 therapy. Interestingly, the pulmonary nodes did not demonstrate any uptake on the WBS before or after receiving I-131 therapy. Patient continues with no pulmonary symptoms and her thyroglobulin (Tg) level continues to be low. She underwent extensive workup that ruled out infections and other malignancy causing the pulmonary nodes. The most recent chest CT, six months after I-131 therapy, showed a slight decrease in the pulmonary nodes. She underwent repeat WBS, 10 months after I-131, notable for minimal uptake in the lungs. The patient is currently euthyroid on thyroid hormone replacement therapy, and she is undergoing surveillance with laboratory studies every three months, neck US and chest CT every six months. Conclusion: In children with PTC, the pulmonary metastases usually demonstrate radioactive iodine uptake, making them responsive to I-131 treatment. Even though the pulmonary nodes were not iodine avid for our patient based on the WBS, it seems like they are responding to the first dose of I-131 as they have decreased in size. Pulmonary metastases in children have different behavior than in adults, and studies have shown that clinical response to I-131 therapy may take several years to show a reduction in the size of nodes. Therefore, careful consideration should be made before giving another dose of I-131 to this group of patients.