A case of thyroid-type papillary carcinoma derived from ovarian mature cystic teratoma, resected by laparoscopic surgery.

Follicular variant thyroid-type papillary carcinoma (FVTPC) arising from thyroid tissue in mature cystic teratoma of the left ovary is extremely rare, and it is not easy to diagnose preoperatively. However, with reports of an early postoperative death, we must prudently select the strategy for this lesion. A 50-year-old woman had a uterine fibroid with hypermenorrhea and a left ovarian tumor measuring approximately 8 cm diameter. Serum thyroid-stimulating hormone level was within the normal limit. A laparoscopic hysterectomy and left salpingo-oophorectomy were performed. During surgery, there were no signs of invasion or metastasis, and there was no spillage in the abdomen. On histopathological examination of the left ovary, we diagnosed FVTPC arising from thyroid tissue in mature cystic teratoma of the left ovary. FVTPC in ovarian struma is a rare malignant transformation. We must be aware of the possibility of such a rare malignant disease when treating teratoma laparoscopically.