Malignant transformation of mature cystic teratoma (MCT) is rare. Sarcomatoid carcinoma is a neoplasm comprising malignant mesenchymal cells and a conventional carcinomatous area. Here, we report on a case of sarcomatoid carcinoma arising from an MCT in the left ovary of a 45-year-old female. A unilocular cyst consistent with MCT was observed; however, a nodule within the cyst was confirmed from the resected ovary. Microscopically, the nodule showed both squamous cell carcinoma and pleomorphic sarcomatous components admixing with each other. Lining epithelial cells at the periphery of the main tumor showed squamous metaplasia. When a sarcomatous component is observed in the ovary tumor, it is important to find a squamous cell component, either benign or malignant.

• Ho-Chang Lee(Department of Pathology Chungbuk National University) Corresponding author
• Seung-Myoung Son(Department of Pathology Chungbuk National University)
• Yong-Moon Lee(Department of Pathology Chungbuk National University)
• Ji Hae Koo(Department of Pathology, Gangbuk Samsung Hospital,College of Medicine, Sungkyunkwan University)
• Song-Yi Choi(Department of Pathology Chungbuk National University)
• Ok-Jun Lee(Department of Pathology Chungbuk National University)
• Eun-Hwan Jeong(Department of Obstetrics and Gynecology, College of Medicine, Chungbuk National University)