Treatment and follow-up of malignant struma ovarii: Regarding two cases

•Malignant struma ovarii is a rare ovarian tumor, corresponding to thyroid carcinoma.•It is generally diagnosed after surgical resection of an ovarian mass.•Iodine 131 therapy can be proposed for adjuvant therapy, after total thyroidectomy.•Follow-up must be extended for 20 years, using thyroglobulin level as a tumor marker.

Malignant struma ovarii (SO) is a rare tumor, and as a consequence, treatments and follow-up procedures are not clearly established. Presented in this study are two cases of suspicious ovarian masses, resected and corresponding to malignant SO on histopathology. Similar to thyroid cancer, we proposed complementary radioiodine therapy (131I) after total thyroidectomy (no malignancy was observed at this level in our two patients). Patients underwent treatment with 3.7 GBq 131I followed by post-therapy whole-body scintigraphy, which can detect residual disease or occult metastases. Thyroid remnant ablation increases the sensitivity and specificity of follow-up testing using serum thyroglobulin levels as a tumor marker. Our two patients remained disease-free for 3 and 5 years, respectively, after treatment.