S3409 A Rare Case of Follicular Thyroid Carcinoma Metastatic to the Pancreas

Introduction: Twelve percent of all thyroid cancers are of the follicular type. Distant metastasis is present in 10-15% of patients diagnosed with follicular thyroid carcinoma, most commonly in the bones and lungs. Pancreatic metastasis is very rare with only 11 cases reported in published literature with most of them involving papillary thyroid cancers. We present a case of follicular thyroid carcinoma metastatic to the pancreas. Case Description/Methods: A 77-year-old man with a past medical history of follicular thyroid carcinoma stage pT3 NX M1 with pulmonary and skin metastasis at presentation. The patient underwent a total thyroidectomy with findings of a 9.5 cm follicular thyroid carcinoma with vascular invasion, but no evidence of invasion beyond the thyroid gland. Positron emission tomography computed tomography revealed nodular densities within both lungs. He had a non-healing skin lesion on the top of his scalp, with excisional biopsy consistent with metastatic follicular thyroid carcinoma. His iodine scan was negative making him not a candidate for radioactive iodine treatment. Nine years after diagnosis, he was referred to gastroenterology for a developing solid 3 cm pancreatic mass on magnetic resonance imaging abdomen. Endoscopic ultrasound with fine needle aspiration revealed a hypoechoic pancreatic body mass and fine needle aspiration showed poorly differentiated carcinoma with immunostains consistent with thyroid origin. The patient received tyrosine kinase inhibitor treatment with Lenvatinib which was stopped after 2 months due to severe arthralgia and myalgia. Discussion: Pancreatic metastasis from follicular thyroid carcinoma is extremely rare. The patient had a relatively indolent course of his metastatic disease for 9 years since diagnosis until he presented with a pancreatic mass. The goal of the treatment continues to be palliative.