MON-347 From Asthma to Papillary Thyroid Cancer: A Rare Case of Substernal Goiter Presenting with Respiratory Distress

Abstract Disclosure: S. Mahmoud: None. C.G. Rivas Pajuelo: None. We present the case of a 20-year-old female with medical history significant for asthma, who presented to the emergency department with complaints of difficulty breathing, wheezing, and coughing for 3 days. On presentation, the patient was tachypneic with increased work of breathing. She received standardized asthma treatment with solumedrol, intravenous magnesium, and continuous nebulized albuterol. Chest X-ray revealed prominence in the right hilar region but no consolidations. Computed tomography angiography was negative for pulmonary Embolism but revealed a partially visualized symmetric, mass like enlargement of the thyroid gland resulting in tracheal narrowing. It also showed masses in the superior and anterior mediastinum. An enlarged lymph node in the superior mediastinum on the left measures 3.1 × 2.9 cm and a pre-vascular mass measures 6.5 x 4.5 cm. Thyroid function tests showed Thyroid Stimulating Hormone of 0.38, Free T4 0.97. Thyroid ultrasound showed markedly enlarged, diffusely heterogeneous and multinodular thyroid gland with hyperemic blood flow. Patient developed an inability to manage oral secretions, a muffled voice, and stridor. She was transferred to the Intensive Care Unit, where she was intubated for airway protection. Ultimately, she was transferred to a hospital with endocrine surgery and underwent a right lobectomy and isthmectomy with resection of right mediastinal goiter. Almost 16cm of right thyroid lobe with mediastinal extension was removed. The case took four hours longer than expected due to technical difficulty and deep extension to the mediastinum. Final pathology report revealed papillary thyroid carcinoma, with BRAFV600. She will be having completion thyroidectomy in the following months and may potentially require radiation therapy depending on the outcome. The majority of cases of substernal goiter are benign, with only a small percentage exhibiting malignant features. Studies indicate that approximately 5–15% of substernal goiters are malignant, with papillary thyroid carcinoma (PTC) being the most common malignancy in these cases. The presence of the BRAFV600 mutation has been strongly associated with increased aggressiveness in PTC, and may also correlate with a higher risk of recurrence. Prognosis for patients with substernal goiter depends on the histological nature of the goiter, with malignant cases requiring more intensive monitoring and treatment strategies to reduce the risk of recurrence. •Persistent wheezing is a concerning sign and a proper neck exam should be performed •With any sign of airway compromise, plans for surgery should be arranged promptly•Most substernal goiter cases are benign, but pathology testing is important, because malignant origin has risk of metastasis, recurrence, and might need additional treatment Presentation: Monday, July 14, 2025