RESUMEN
Struma ovarii exhibiting malignant histology are uncommon, and aggressive clinical courses with initial extraovarian spread are even more rare. This report describes a case of malignant struma ovarii with a predominant anaplastic carcinoma component. A 65-yr-old, gravida 2, para 2, female presented with lower abdominal discomfort and pain. She had a 12×10×7.5 cm tumor in the right ovary. Intraoperative diagnosis was high-grade spindle cell tumor. Right salpingo-oophorectomy and hysterectomy were performed. Macroscopically, the tumor invading the right tube was a yellow-white solid mass with focal microcysts containing greenish liquid and focal calcification. The tumor was histologically characterized by a spindle cell and pleomorphic sarcomatous component, and a minor component of benign-looking thyroid tissue with ossification. Immunohistochemically, the sarcomatous component was focally positive for CAM 5.2, EMA, thyroid transcription factor-1, and thyroglobulin, indicating anaplastic carcinoma. The patient was treated with chemotherapy and is alive, yet with tumor, 25 mo after surgery. This is the first case of malignant struma ovarii with a predominant component of anaplastic carcinoma. This type of malignant struma ovarii may lead to diagnostic problems, and sampling and differential diagnosis among sarcomatous ovarian tumors are important for making the correct diagnoses.