Introduction/Background Struma ovarii (SO) is a rare tumor composed of mature thyroid tissue. It represents 5% of all ovarian teratomas and its malignant presentation is even more rare (less than 5%). SO often manifests with symptoms typical of ovarian cysts: intermittent abdominal pain, abdominal mass or bleeding disorders. However, it can occasionally present with complex syndromes: 5% of patients show features of hyperthyroidism or thyroid gland enlargement.

Methodology We retrospectively searched cases of SO in our center. Data concerning symptomatology, diagnostic approach and treatment was reviewed. Additionally, we aimed to evaluate the current knowledge regarding clinical presentations, ultrasonographic description, use of other complementary tests and therapeutic management. Therefore, a systematical review following PRISMA guidelines was performed.

Results Six cases with histologically confirmed SO were retrospectively reviewed. Each of the patients consulted for a different reason, was initially suspicious of a different diagnose, suffered a different evolution, and therefore went under a different management. For the systematic review, 13 articles were included in the final analysis after applying inclusion and exclusion criteria. Selected articles provided data for 353 tumours (161 cases classified as benign, including 3 cases of strumosis, and 158 as malignant). Information regarding patients’ characteristics, clinical presentation, thyroid gland affection, diagnostic tests and treatment were collected.

Conclusion Our series of patients confirms diagnose based on clinical manifestations or imaging studies is rather complicated, as clinical presentations are widely diverse. Such as reflected in the systematic review, the most common symptoms are abdominal pain and mass. Thyroid gland affection is infrequent. Histological confirmation is required to stablish diagnose. Surgical treatment is sufficient for benign lesions, and even if secondary conditions such as thyroid hyperfunction or ascites occur, these regress upon removal of the tumor. The optimal treatment for malignant SO is extensive pelvic surgery followed by thyroidectomy and radioactive iodine therapy.

Disclosures Nothing to declare.