SAT-072 A Case of Solitary Hyperfunctioning Thyroid Nodule Harboring Papillary Thyroid Carcinoma in a Pediatric Patient

Introduction: Thyroid nodules are less common among children than adults but are more likely to be malignant. Among all the thyroid nodules, autonomous functioning thyroid nodules (AFTN) are generally considered to be a benign entity, with malignancy found in less than 1 %. AFTN are very rare in the pediatric population, and the optimal treatment is not well defined. We present a 14-year-old female patient with an AFTN treated with surgical resection and found to contain papillary thyroid carcinoma, despite a previous biopsy which did not demonstrate malignancy. Case presentation: A 14-year-old girl presented with left-sided palpable thyroid lesion for four months. The patient had no symptoms at that time, and the physical exam was notable for a palpable left thyroid nodule measuring 3x 2.2 cm. Thyroid studies were remarkable for a suppressed thyroid-stimulating hormone (TSH) of 0.056uIU/mL (0.350–4.94), normal free thyroxine (FT4): 1.1 ng/dL (0.7–1.5), and positive anti-thyroglobulin antibodies: 9.0 IU/ml (0.0 - 4.1) with negative anti peroxidase antibodies and negative thyroid-stimulating immunoglobulin. Initial ultrasound (US) showed a left complex cystic and solid nodule measuring 3.4 cm x 1.8 cm x 2.3 cm. Fine needle aspiration (FNA) of the nodule revealed a benign aspirate. An I-123 scan revealed a hyperfunctioning nodule with suppression of uptake in surrounding thyroid parenchyma. The patient was then lost to follow up, presenting to our clinic over a year later due to difficulty breathing when supine and increased nodule size. Thyroid studies were notable for a suppressed TSH of 0.005 and slightly elevated FT4:1.8. Thyroid US showed a mixed cystic and solid nodule measuring 4.7 x3 x 4cm, with no calcification. Given the increased size of the lesion, her age, and difficulty breathing when supine, a decision was made to proceed with left hemithyroidectomy for definitive diagnosis and treatment. Pathology of the specimen revealed an encapsulated papillary thyroid carcinoma with focal capsular invasion. Right hemithyroidectomy was performed three weeks later, followed by I-131 ablation one month after surgery. The patient is currently doing well and euthyroid on thyroid hormone replacement therapy, with no evidence of disease. She is undergoing surveillance with ultrasound imaging and laboratory evaluation. Conclusion: This is a rare case of AFTN harboring papillary thyroid carcinoma. Although the majority of cases of AFTN are benign, an FNA was performed and was negative for malignancy. Due to an increase in size, new symptoms and ultrasound changes, surgery was performed and revealed the final diagnosis. The behavior of thyroid nodules in pediatric patients can be different than adult patients. Even though the majority of AFTN are benign, we should still keep malignancy in our differential when the nodule has a growth pattern, new US findings or patient develops worsening symptoms.