SUN-LB80 Thyroglossal Duct Cyst Carcinoma in a 12 Year Old Boy. Should Total Thyroidectomy Be Done?

INTRODUCTION The thyroglossal duct cyst (TGDC) is the most common congenital anomaly of the neck in childhood. However, thyroid carcinoma of the thyroglossal duct cyst is rare. It occurs in less than 1% of cases and the diagnosis is usually made from histopathologic findings after cyst surgery. Papillary carcinoma is the most common histologic subtype. The management of the TGDC carcinoma is not well defined. Sistrunk procedure (resection of the cyst and hyoid bone) followed by total thyroidectomy is the classic treatment, due to frequency of concomitant thyroid cancer (20-60%). However some authors propose a more conservative management performing thyroidectomy only in certain cases (positive margins, abnormal preoperative imaging, extension of TGDC carcinoma beyond the cyst wall). Lymph node resection and radioactive iodine therapy are used on advanced stages. CLINICAL CASE A 12-year-old boy presented with a four-month history of neck swelling. There was no previous exposure to irradiation or positive family history of thyroid cancer. Physical examination revealed a 5 cm mass located in the midline region of the neck, slightly tilted to the left, above the hyoid bone, covered by normal skin. A neck ultrasound was performed showing a normal thyroid gland, and a cystic lesión compatible with a TGDC. A CT scan corroborated this finding, showing a cystic lesión of about 3.1 cm x 2.1 cm x 3.7 cm (anteroposterior, transverse and craniocaudal planes) with a small solid pole in the posterior portion of the cyst, 1x1 cm on the axial plane. Small cervical lymph nodes with no suspicious features were also described. Thyroid function tests were normal. Sistrunk operation was performed for resection of the TGDC. Histologic examination revealed papillary carcinoma in a thyroglossal duct cyst. It measured 17 mm at its maximal diameter and invaded the cyst wall 1 mm with negative margins. Consequent to the diagnosis of TGDC carcinoma, total thyroidectomy was performed on a second surgery whithout side effects. Thyroid tissue showed usual morphological features without signs of malignancy. Currently the patient undergoes levothyroxine replacement treatment.CONCLUSIONS Papillary thyroid carcinoma in thyroglossal duct cysts is rare entity and even rare in children. Given that several studies in adults show a non-negligible percentage of patients with TGDC carcinoma and a normal thyroid ultrasound who had a concomitant thyroid cancer, the most controversial part of its management is whether total thyroidectomy should be done or not. Although some groups advocate thyroidectomy only in specific cases of TGDC carcinoma, its multifocal nature and the low risk of complications of thyroid surgery in pediatric referral centers make us supporters of performing total thyroidectomy to all patients.