ODP497 Multifocal Papillary Thyroid Carcinoma with Anaplastic Dedifferentiation

A 71-year old male with a two-year history of progressively enlarging right thyroid mass presented with hemoptysis. Chest CT scan showed multiple pulmonary nodules and enlarged right thyroid mass with intrathoracic extension. A fine needle biopsy of the right thyroid mass showed atypia of undetermined significance. Patient underwent total thyroidectomy and complete resection of the intrathoracic component. Histopathology reported multifocal Papillary thyroid carcinoma, right lobe, encapsulated follicular variant (9cm) with extensive and vascular invasion. There was also invasion of the left thyroid lobe, follicular variant, infiltrative (0.6 cm) and conventional (0.6 cm). Extrathyroidal extension to skeletal muscle and lymphovascular invasion was present. The tumor showed areas with more solid growth patterns and some ball-like clustering. Consequently, immunostaining was done which showed the following results: positive for cytokeratin, thyroglobulin and TTF-1 consistent with papillary morphology. The more solid areas with significant nuclear pleomorphism, necrosis and increased mitotic activity (atypical forms) support the focal progression to an anaplastic carcinoma. The final histologic reading showed multifocal papillary thyroid carcinoma with focal (20%) progression to undifferentiated (anaplastic) thyroid carcinoma. Two weeks postoperatively, he developed a 4cm×2cm manubrium mass. There were also several metastases on the brain, pancreas, liver and bones seen on FDG PET scan. One month postoperatively, TSH was 15 uIU/mL Thyroglobulin >500 uIU/mL, anti-thyroglobulin <0.20 ng/dl. Due to the widespread metastases even involving the brain, the multidisciplinary team decided to start treatment with Lenvatinib and check for BRAF V600E gene mutation for a more definitive treatment. He was started on Levothyroxine. He also underwent 27 cycles of radiation therapy to the manubrium mass and was given Denosumab 120mg subcutaneously to stabilize the bone and provide pain relief. BRAF gene mutation analysis result came back negative in two weeks. Close monitoring of his sensorium was done. However, he deteriorated clinically and he succumbed to sudden cardiac death two months after. Presentation: No date and time listed