SUN-599 A Case Of Synchronous Follicular, Medullary, And Follicular Variant Of Papillary Carcinoma In A Single Thyroid Gland: A Lesson In Integrating Management

Background: The presence of multiple distinct types of thyroid cancer within the same thyroid gland has been described but is rare. Medullary thyroid carcinoma is managed differently from other forms of differentiated thyroid cancer when presenting solely. Clinical Case: A 59 year old woman presented to her primary care provider complaining of a neck lump. A thyroid ultrasound revealed a 3.4 cm right thyroid lobe nodule. FNA was performed and suspicious for a follicular neoplasm. A right hemithyroidectomy and isthmusectomy revealed a 3.0 cm at least minimally invasive follicular carcinoma with involved margins with pathologic diagnosis limited by the anterior surface of the thyroid having been disrupted during surgery. There also was an incidental 1.5 mm medullary carcinoma noted. A left completion thyroidectomy then found a 1 mm follicular variant of papillary carcinoma. She was referred for further subspecialty Endocrinology and ENT care for her stage II or higher follicular cancer along with medullary and follicular variant of papillary microcarcinomas. Laboratory evaluation included a TSH of 10.800 (0.360-3.740 mIU/L), thyroglobulin 7.0 (1.5-38.5 ng/mL), thyroglobulin antibody < 1.0 (0.0-0.9 IU/mL), calcitonin < 2.0 (0.0-5.0 pg/mL), CEA 1.3 (< 3.0 ng/mL), calcium 8.8 (8.5-10.1 mg/dL), PTH 36 (14-64 pg/mL), vitamin D 30 (30-100 ng/mL), plasma normetanephrines 38 (0-145 pg/ml), plasma metanephrines 10 (0-62 pg/mL), and RET mutation negative. Her postsurgical hypothyroidism was treated with levothyroxine doses titrated to goal TSH < 0.1. Contrasted neck CT revealed postsurgical changes with no concerning adenopathy. These findings led to a decision against reoperation to include neck dissection but delayed radioactive iodine treatment. Approximately 2.5 months after her iodinated contrast exposure, she was treated with 100 mCi of radioactive iodine 131 via Thyrogen stimulation. Posttreatment whole body scan showed uptake at the thyroid bed but was negative for metastatic disease. Subsequent calcitonin was < 2.0 and CEA 0.7 with ultrasound only showing a 0.4 mm hypoechoic nodule versus node in the right thyroid fossa. One year after her completion thyroidectomy and six months after ablation, TSH was 0.019, thyroglobulin 0.1, thyroglobulin antibody < 1.0, calcitonin < 2 (≤ 5 pg/mL), CEA 0.8, and ultrasound was free of any concerning lesions. She remained on suppressive levothyroxine and further surveillance performed via Thyrogen stimulation with thyroglobulin < 0.1, thyroglobulin antibody < 1.0, and radioactive iodine whole body scan negative for evidence of disease. Clinical Lesson: Coincident follicular thyroid cancer with medullary and follicular variant of papillary thyroid cancer is rare but each malignancy can be managed concurrently yet independently of the other as per current practice standards.