5-Fluorouracil (5-FU) is a chemotherapeutic agent frequently used for the treatment of solid tumors. In a few cases, 5-FU can be associated with coronary vasospasm, cardiac ischemia, or life-threatening arrhythmias. Recognition of 5-FU cardiotoxicity is clinically important as after the rapid sensation of therapy, cardiotoxicity can be completely reversible, and on the other hand, readministration may lead to serious damage of the heart and even death. A 70-year-old male came to the emergency department (ED) with chest pain which started while receiving an infusion of 5-FU. The patient did not have a personal history or risk factors of coronary artery disease and his electrocardiogram (ECG) before starting chemotherapy was completely normal. In the ED, his ECG had ischemic changes, troponin was elevated, and echocardiogram showed anterior wall hypokinesis. However, emergent coronary angiogram did not reveal any acute coronary occlusion. 5-FU-induced cardiotoxicity was suspected; the patient was admitted to a progressive care unit for close monitoring and infusion of calcium channel blockers was initiated. The patient’s symptoms and ECG findings gradually resolved, and two days later on discharge, patient was chest pain free and ECG was normal. This case supports the vasospastic hypothesis of 5-FU cardiac toxicity, describes its clinical course, and emphasizes the importance of better awareness and early recognition of the rare side effect as it may allow physicians to reduce the risk of life-threatening complications.

Introduction: Solitary fibrous thyroid nodules are rare tumors and can mimic benign thyroid goiter and neoplasms. Case Description45 years old Caucasian female, with no significant past medical history, who presented to endocrinologyclinic for left neck mass evaluation. She denied previous history of thyroid disease, weight loss, cold/heatintolerance, menstrual irregularity, toxic or obstructive thyroid related symptoms. Her family history issignificant for maternal pancreatic cancer. Clinical exam was unremarkable except for left thyroid mass. An initial thyroid ultrasound showed left thyroid nodule 20 x16 x 25 mm in size five years prior topresentation. Repeated Fine Needle aspiration yielded benign follicular cells, histiocytes and fewlymphocytes. The nodule continued to increase in size reaching 46 mm in the long axis per thyroidultrasound at presentation to clinic. Her TSH, FT4 and total T3 remained within normal ranges. She wasreferred for surgical evaluation and underwent left thyroid lobectomy. Pathology reported 50 mm wellcircumscribed intrathyroidal neoplasm composed of spindle cells with pauci to moderate cellularity with noincreased mitotic activity, nuclear atypia, or necrosis. Immunohistochemistry was positive for STAT 6 andCD34and negative for PAX-8, TTF-1, S100 and SMA. The patient remains euthyroid with no lymph nodeor organ involvement after 5 years from initial presentation. Discussion: Solitary fibrous tumors (SFT) of the thyroid are rare although they have been described in differentanatomic sites (1). It presents as slow growing, painless, non toxic nodule in middle age of both sexes (1,2). The diagnosis of these tumors via FNA is difficult due to cellular paucity. Histologic findings may bechallenging due to shared features with other thyroid undifferentiated, papillary and follicular cancervariants. Immunohistochemistry are warranted to assist in confirmation-STAT6 and CD34 (3). SFT tumorsare mostly benign tumors and carries favorable prognosis. References: (1) Thompson, L.D.R., Wei, C., Rooper, L.M. et al. Thyroid Gland Solitary Fibrous Tumor: Report of 3 Cases and aComprehensive Review of the Literature. Head and Neck Pathol13, 597–605 (2019)(2) Ghasemi-Rad M, Wang KY, Jain S, Lincoln CM. Solitary fibrous tumor of thyroid: a case report with review ofliterature. Clin Imaging. 2019;53:105–107. doi: 10.1016/j.clinimag.2018.09.011.(3) Matoso A, Easley SE, Mangray S, Jacob R, DeLellis RA. Spindle cell foci in the thyroid gland: an immunohistochemicalanalysis. Appl Immunohistochem Mol Morphol. 2011;19(5):400–7.

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