Huge follicular carcinoma originated from struma ovarii in young woman; Extremely rare case.

Introduction: Struma ovarii (SO) is a rare ovarian mature teratoma which is composed of 50% or more thyroid tissues. Malignant transformation is reported to occur in less than 5% of all cases, and it leads to 5-6% metastatic disease. The most common type is a papillary carcinoma. However, follicular carcinoma of arising from SO is extremely rare.

Case Presentation: A 23-year-old nullipara complained of right lower abdominal pain. CT scan revealed a large complex cystic and solid mass in pelvic cavity with moderate amount ascites with peritoneal thickening and omental infiltration. We performed a right salpingo-oophorectomy and surgical staging.

Clinical Discussion: It was diagnosed with follicular carcinoma, stage IA. After the multidisciplinary team meeting, we decided not to conduct additional treatment, including total thyroidectomy followed by radioiodine treatment and T4 therapy because thyroid tests were normal findings.

Conclusion: There is still no established treatment consensus for follicular carcinoma of SO patients. The choice for a conservative or radical approach depends on the doctor. However, conservative surgery could be considered for low risk, early stage patients who have childbearing potential.