SUN-486 Unusual Presentation of Metastatic Follicular Thyroid Cancer

Distant metastasis of follicular thyroid cancer to the bone has been well documented. However, spinal cord compression as the initial presentation of metastatic follicular thyroid cancer without any thyroid symptoms is relatively rare. Here we discuss such a case. A 78-year-old female with history of HTN and melanoma presented to the ED with a 1-month history of middle back pain that progressed to lower extremity weakness, numbness, and inability to ambulate. MRI showed a T7 vertebral mass with cord compression and edema. Metastatic work up was unremarkable except for incidental bilateral thyroid nodules, the largest on the right lobe, at 1.6 cm, with peripheral calcifications. The patient underwent T6-T7 laminectomy with vertebral decompression, partial colpectomy, and T4-T10 fusion. Pathology of the thoracic vertebral mass was positive for CAM 5.2, cytokeran 7, TTF-1, and PAX8 consistent with either metastatic pulmonary adenocarcinoma or thyroid carcinoma. The patient denied shortness of breath, dysphagia, hoarseness, or neck tenderness. She had no personal history of hyperthyroidism or hypothyroidism, or radiation exposure. She also did not have any family history of thyroid cancer. Laboratory work up was significant for TSH of 3.71 mcU/mL (0.4-4.0 mcU/mL), Free T4 1.56 ng/dL (0.7-1.9 ng/dL), thyroglobulin (Tg) 6940 ng/mL (1.6-55.0 ng/mL), and thyroglobulin antibody (Tg Ab) 20 IU/mL (0-115 IU/mL). FNA of the right thyroid nodule showed follicular neoplasm with very similar morphological features to the epidural pathology, favoring a follicular carcinoma. She underwent total thyroidectomy. Pathology showed a 1.6 x 1.1 cm follicular carcinoma with capsular and angiolymphatic invasion, but with uninvolved margins of resection. TNM staging was pT1b, pNx, pM1. She was ablated with 109 mCi of I-131 after withdrawal therapy. Whole body scan after treatment revealed radioiodine avid metastatic disease at T7 and activity in the thyroid bed compatible with residual thyroid tissue. Patient completed 10 fractions of external beam radiotherapy to the spine for a total of 30 Gy. Three months follow up lab work showed Tg 580 ng/mL and negative Tg Ab with a suppressed TSH. Thyroid bed ultrasound did not show any residual tissue or abnormal lymph nodes. Ten-year survival rates in patients with bony metastatic differentiated thyroid cancer range from 13-21% (1). Metastatic thyroid carcinoma should be considered in the differential diagnosis of every patient with new onset bony metastasis and thyroglobulin should be considered as a tumor marker in the initial work up. Research shows increased survival with I-131 avidity and complete bone metastasis resection (1). 1. Ramadan, Sami et al. “Spinal metastasis in thyroid cancer.” Head & neck oncology vol. 4 39. 25 Jun. 2012, doi:10.1186/1758-3284-4-39