BACKGROUND: Thyroid-type carcinoma in struma ovarii (SO) is a very rare neoplasia which can sometimes be difficult to diagnose and treat because of the relatively poor knowledge of the disease. CASE: A 52-year-old woman with a right ovarian neoformation presented with abdominopelvic pain. A bilateral salpingo-oophorectomy was performed, and histopathological examination revealed a right ovarian teratoma in which thyroid tissue harbored a nonencapsulated follicular variant of papillary carcinoma. Total thyroidectomy ruled out metastasis from a primary thyroid tumor, and histopathological examination revealed no evidence of thyroid malignancy. Radioactive iodine therapy was performed 4 months after thyroidectomy, and the patient showed no evidence of recurrent or persistent disease after 14 months of follow-up. CONCLUSION: Papillary thyroid-type carcinoma is reported as the most common thyroid-type carcinoma in SO and yet is a very rare disease, with only 18 cases reported in the English literature in the last 9 years. No consensus has been reached among pathologists in diagnostic criteria nor among clinicians in treatment strategy. CONCLUSION: As thyroid-type carcinoma in SO is a rare disease, much effort is needed in developing adequate diagnostic criteria and treatment modalities. © Science Printers and Publishers, Inc.