SAT552 Thyroid Mass With Both Anaplastic, Papillary Carcinoma Treated With Surgery, Radiation Therapy, Paclitaxel Chemotherapy

Disclosure: T.H. Hoang: None. D. Whiteman: None. P. Luceri: None. V. Del Signore: None. Introduction: Anaplastic thyroid carcinoma, while rare, is extremely aggressive and overall survival is poor. Median survival is a mere 4 months from time of diagnosis and mortality approaches 100%. We present a case of anaplastic thyroid carcinoma in the setting of differentiated thyroid carcinoma that has shown response to total thyroidectomy, radiation, and chemotherapy over the course of several months. Case Presentation: A 58 year old female who originally presented with the sensation of a lump in her throat in 2012. Thyroid ultrasound at that time revealed a thyroid mass (3 x 2 x 2 cm, mixed echogenicity) of the right thyroid lobe. Two thirds of the mass was solid with increased vascularity; the remaining was cystic. Originally, cytology revealed benign follicular cells, colloid, Hurthle cells and macrophages, and was negative for malignancy. She was diagnosed with a nodular goiter and she was lost to follow up. She again complained of a 15 pound weight loss associated with a lump in her neck in 2021. A repeated thyroid ultrasound revealed a 7cm right sided thyroid nodule with mass effect on the trachea. Repeated cytology showed atypia of undetermined significance. Molecular analysis was positive for EIF1AX, NRAS, & TERT mutations. ENT recommended a total thyroidectomy due to the molecular mutations and the patient’s compressive symptoms. Surgical pathology was consistent with a right-sided, anaplastic thyroid carcinoma arising from an encapsulated, well-differentiated thyroid carcinoma confined to the thyroid and measuring 5.5 cm (Stage IV CT3a, cN0, cM0). Interestingly, the anaplastic component of the tumor was only 15% of the overall mass with the other portion being well-differentiated papillary thyroid carcinoma. She received 6000cGy of external beam radiation with concurrent paclitaxel (60mg/m(2)) for 6 weekly cycles. A PET/CT four months later showed no evidence of local or distant metastatic disease. CT Chest, Abdomen, Pelvis with contrast did not reveal metastatic disease either. Later, CT soft tissue of her neck showed no residual or recurrent tumor. MRI Brain was negative for acute findings, including metastatic disease. At the current time, she is 18 months from her original diagnosis of anaplastic thyroid carcinoma. She continues to follow with medical oncology and endocrinology and there has been no evidence of recurrent disease. Discussion: When present, it is common for anaplastic thyroid carcinoma to be associated with both papillary and follicular thyroid carcinoma. Regardless of association, anaplastic thyroid carcinoma remains aggressive and median survival is measured in months. Treatment includes surgery, radiation and chemotherapy which can contribute to an increase in 2 year survival to 42% from 18% without treatment. Advancements in the treatment of anaplastic thyroid carcinoma are needed as the recurrence of aggressive disease is unfortunately expected. Presentation Date: Saturday, June 17, 2023