SAT558 Papillary Thyroid Carcinoma With Anaplastic Transformation in a Filipino Male Treated With Radioactive Iodine and Radiotherapy: A Case Report

Disclosure: A.A. Apa-ap: None. P. Abarquez: None. M.B. Sedurante: None. A. Ongbit: None. P. Carlos Miguel: None. F. Acenas: None. J. Gacula: None. V. Lee: None. S. Estreller: None. INTRODUCTION. Papillary thyroid carcinoma (PTC) is an epithelial malignancy showing follicular differentiation and distinctive nuclear features, with a generally excellent prognosis. On the other hand, anaplastic thyroid cancer (ATC) is rare and highly lethal, with an incidence of only 0.7% in the Philippines. CASE DESCRIPTION. This paper describes a 43year old Filipino male with a 3-year history of anterior neck mass with an initial fine needle aspiration biopsy read as probable PTC. He underwent total thyroidectomy and bilateral radical lymph node dissection and histopathology revealed conventional PTC, solid variant with 5% focal anaplastic transformation. Metastatic workup revealed multiple sub-centimeter pulmonary nodules and a tiny hypodense nodule on left adrenal gland on CT scan. Bone scintigraphy showed increased tracer uptake in the posterior 10(th) rib and the sphenoid's greater wing. While the multidisciplinary team wanted to proceed with Radiation therapy (RT) first to address the more aggressive histology, this was not possible logistically and thus RAI was performed first. This slight deviation from guidelines was deemed acceptable by Nuclear Medicine due to the possible decrease in iodine absorption from post radiation fibrosis. After a dose of 150 mci, 4 weeks after surgery, patient then completed 33 fractions of RT. Surveillance revealed stable pulmonary nodules and adrenal mass but increasing TSH-stimulated thyroglobulin and antithyroglobulin. Patient underwent another cycle RAI and is currently stable on his 16th month from diagnosis, 15th month post initial RAI, and 13th month post-RT. DISCUSSION. In several case series, patients with minor anaplastic component had 1- and 2-year survival rates of 88% and 43%, respectively with a median survival of 17 months. The overall prognosis of patients with PTC with minor ATC component points to the value of active surveillance compared to more aggressive treatment modalities in the setting of conventional ATC. Presentation Date: Saturday, June 17, 2023