Undifferentiated high grade pleomorphic sarcoma of the thyroid gland is very rare. A 70-year-old woman was referred to our hospital for evaluation of a rapidly growing mass in the right lobe of the thyroid gland. At the first visit, she had no symp-toms. Fine-needle aspiration cytology revealed an atypia of undetermined significance. She revisited our hospital after 17 days. At that time the mass had become more enlarged and she complained of dyspnea. The next day, surgery was performed and the diagnosis was undifferentiated high grade pleomorphic sarcoma of the thyroid. The patient died 119 days after sur-gery.

• 나상돈(순천 성가롤로병원 내분비내과) | Sang Don Na
• 김병기(순천 성가롤로병원 내분비내과) | Byung Ki Kim
• 진석재(순천 성가롤로병원 내분비내과) | Suk Je Jin
• 정용진(순천 성가롤로병원 내분비내과) | Yong Jin Jeong
• 강미연(순천 성가롤로병원 내분비내과) | Mi Yeon Kang
• 김정민(순천 성가롤로병원 내분비내과) | Jung Min Kim Corresponding author