Malignant struma ovarii, a rare manifestation of differentiated thyroid cancer within ovarian teratoma, poses challenges in management due to its unpredictable behawior, as well as risk of recurrence and metastasis. This study explores the treatment and prognosis of this rare entity, focusing on the controversies surrounding surgical extension and adjuvant therapy.

A retrospective analysis was conducted on data from patients qualified for further treatment in the Department of Endocrine Surgery after the prior diagnosis of malignant struma ovarii, with a focus on the clinical course and management strategy.

Six women (aged 28-69) underwent surgical adnexectomy for ovarian tumor in 2018-2023. The histopathological findings indicated the presence of differentiated thyroid carcinoma arising within ovarian teratoma in each case. Subsequently, total thyroidectomy followed by radioiodine therapy was administered. Among them, microfoci of papillary carcinoma(pT1a:1-7 mm) were also detected in the thyroid in 4 cases. Twice, distant metastases were found (to the vertebral bones and perirenal lymph nodes). In 1 case, no infiltration of cancer was found in the post-thyroidectomy specimen, nor were there any metastatic changes.

The aggressiveness of the management strategy for incidental findings of thyroid cancer in ovarian cysts is still under discussion on a case-by-case basis. Our experience emphasizes the necessity for adjuvant treatment with total thyroidectomy followed by radioiodine therapy, regardless of patients' age and fertility, even in the absence of suspected changes in the cervical thyroid. One should always consider the high potential for distant metastasis and the likelihood of the simultaneous occurrence of concealed thyroid malignancies.