A wide variety of tissues derived from the three germ layers are seen in ovarian teratomas. Microscopically, the most commonly seen tissues are epidermis, skin adnexa, and neural tissues. Thyroid tissue is present in 10% of ovarian mature cystic teratomas. In this case, report, we present a rare case of papillary microcarcinoma derived in the ovarian teratoma and Hashimoto's thyroiditis with the normal level of serum thyroid hormones, which is normal but positive serum antithyroid peroxidase antibodies.
Keywords: Hashimoto's thyroiditis; malignant transformation; mature cystic teratoma; papillary thyroid carcinoma.