SUN-281 - An Unusual Case of Stage IVB Anaplastic Thyroid Carcinoma

Introduction: Anaplastic thyroid carcinoma (ATC) is a rare and highly aggressive form of thyroid carcinoma that carries a poor prognosis. Median survival following diagnosis is 3-6 months with less than 10% of patients surviving 1 year. We present an unexpected case of a resectable, non-metastatic ATC in a young patient despite a large tumor burden and high-risk molecular mutations.

Case: A 49-year-old female with a past medical history of type 2 diabetes mellitus and hypertension presented with a four-month history of a rapidly enlarging neck mass with progressive hoarseness, dysphagia, and wheezing, prompting emergency evaluation. Initial TSH and T4 at the time of presentation were within normal limits. Computed tomography (CT) of the soft tissues of the neck demonstrated a large heterogeneously enhancing solid mass centered within the right thyroid gland with extension into the isthmus, measuring 8.3 x 7.3 x 9.5 cm, with mass effect and leftward deviation of the trachea. A 6-mm hypodense nodule was noted in the left thyroid gland. CT chest demonstrated two non-specific 5-mm pulmonary nodules and a 1-cm splenic lesion. Subsequent magnetic resonance imaging (MRI) suggested that the splenic lesion was benign. A positron emission technology (PET) scan was negative for metastatic disease. Fine needle aspiration biopsy was subsequently complete and demonstrated poorly differentiated malignant neoplasm. The patient was evaluated by otolaryngology and underwent a total thyroidectomy. Histopathologic examination revealed a highly pleomorphic malignant neoplasm composed of epithelioid and spindle cells with increased mitotic activity and areas of tumor necrosis, consistent with anaplastic thyroid carcinoma. Pathologic staging was IVB (pT4a, pNX, cM0). Molecular testing identified TP53 and TERT promoter mutations, with negative testing for BRAF V600E. Postoperatively, the patient was placed on levothyroxine 150 mcg daily and calcitriol 0.25 mcg daily. Following multidisciplinary tumor board discussion, the patient began neoadjuvant radiation therapy with concurrent chemotherapy using carboplatin and paclitaxel. Due to an allergic reaction, she was transitioned to doxorubicin. The patient is actively undergoing treatment.

Conclusion: This case highlights the importance of prompt recognition, comprehensive staging, and multidisciplinary approach to the treatment of ATC. Early identification of non-metastatic disease may allow for aggressive multimodal therapy and potentially improved outcomes, even in tumors with high-risk molecular features.

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