MON-455 Papillary Thyroid Carcinoma in the Thyroglossal Duct

BACKGROUND In the thyroglossal duct (TD) there are remains of thyroid tissue in 1-40%. Thyroid cancer diagnosed in this duct is an uncommon finding, with a prevalence of less 1% and must meet these criteria: identify the TD, locate remains of carcinoma in it; absence of cancer in the thyroid gland and presence of thyroid follicles in the TD. We present a patient with thyroid cancer in the TD. CLINICAL CASE 63-years-old-woman. 18 months ago, she noted a submandibular tumor associated to asthenia, weight loss and tremor. On physical examination: 3cm tumor, increased consistency, near to the hyoid bone and 1.5cm left cervical adenopathy. Blood analysis: TSH 0.01 (0.2-4.5) and FT4 5.53 (0.9-1.7). Hyperthyroidism was diagnosed and she started Tiamazol 10mg/bid and propanolol 20mg/tid. Thyroid US: diffuse goiter. Soft tissue US: heterogeneous mass 39x15x26mm in midline of suprathyroid region suggestive of neoformative process. Cervical CT scan: solid, heterogeneous, neoformative tissue, located in the midline, infiltrating prelaringeal muscles in contact with hyoid bone. Cervical adenopathy in group II on right side and group III and IV on the left side. Increase in thyroid gland volume. FNA US guided of suprathyroid tumor was performed: cytology compatible with papillary thyroid carcinoma, Bethesda VI. FNA left adenopathy: compatible with metastasis papillary carcinoma. Midline tumor exeresis in relation to a TD (Sistrunk surgery), total thyroidectomy plus left lymph node dissection group IIA, IIB, III, IV and V was performed. Surgical findings: Right lobe thyroid 4x3x2cm with 1cm nodule on the upper pole. Left thyroid lobe 6x4x2cm with multiple nodules, the largest one in upper pole, 2cm. Multiple adenopathies. A 3x3x1cm tumor with irregular edges, hard consistency, adhered to the hyoid bone was removed. The histology was compatible with papillary thyroid carcinoma in the TD. Thyroid gland was informed as simple goiter. 150ug of levothyroxine was initiated. Six months later, she receives 100mCi I(131). The total body scan was positive for thyroid remnant in cervical region. TSH 0.8 FT4 1.71. Thyroglobulin (TG) 13.98 and AntiTG 400. One year later, new total body scan was negative. TG 10,3 and antiTG 816. New thyroid US showed group III cervical adenopathy 4x7x3mm. Biopsy was compatible with metastasis of papillary thyroid carcinoma. The patient is awaiting a new surgery for lymph node dissection. CONCLUSION Sistrunk surgery and total thyroidectomy plus lymphadenectomy should be the treatment of choice in thyroid cancer in TD, followed by ablative therapy. This attitude improves long-term follow-up and reduces the risk of recurrence. BIBLIOGRAPHY 1. Granado A, et al. Cáncer del conducto tirogloso. Acta Chir Catal, 8 (1987), 37-44 2. Echenique E. Thyroid cancer arising in a thyroglossal duct cyst. Cir Esp. 2000 67 (6) 567-71.