Malignant struma ovarii in pregnancy: A case report

Struma ovarii are a rare type of cystic teratomas that are composed predominantly or entirely of thyroid tissue and account for less than 1 % of all ovarian tumours. Malignant presentations are even less common, accounting for approximately 5 % of struma ovarii. Due to their rarity, evidence to inform management is very limited. We report a distinctive case of a 27 year-old patient with malignant struma ovarii (MSO) during pregnancy.

The patient presented with acute lower abdominal pain and was treated with a laparoscopic cystectomy for ovarian torsion. Pathology revealed a 3 cm MSO with a component of papillary thyroid carcinoma arising in an 11.2 cm mature cystic teratoma. The patient became pregnant while pathology results were pending. Given the absence of most high-risk features such as presence of surface adhesions, tumor size greater than 5-10 cm, ascites greater than 1 L, or extra-capsular extension, she was deemed suitable for close observation during pregnancy with serial ultrasounds. At term, she underwent an elective repeat cesarean section, with a concomitant completion unilateral salpingo-oophorectomy and omentectomy. Four months later, a recurrence was detected in the abdominal and pelvic lymph nodes, which was managed with cytoreductive surgery and total thyroidectomy, followed by radioactive iodine (RAI) therapy. Three years after her initial diagnosis, the patient remains well without biochemical or radiologic evidence of recurrence.

MSO are rare and treatment should be individualized. In select cases, fertility-sparing management can be considered. The role of thyroidectomy and RAI therapy remains a topic of debate.