From the Guidelines

Malignant struma ovarii should be managed with total thyroidectomy and treated as differentiated thyroid carcinoma.

The primary goal is to remove any residual thyroid tissue, allowing for the use of thyroglobulin as a tumor marker and enabling radio-iodine imaging and ablation to destroy any remaining functioning tissue 1.
Whole body imaging with radio-iodine is essential to search for any other functioning tissue.
This approach may be considered excessive by some, but it has been reported to yield the best outcomes in series where it is standard practice 1.

The surgical approach may vary depending on the patient's age, family status, and extent of disease spread, with hysterectomy and bilateral salpingo-oophorectomy advised for postmenopausal women or those who have completed their family 1.
Conservative surgery may be considered in younger women with no extra-capsular spread and no associated mature cystic teratoma, but completion surgery should be performed when the family is completed 1.

From the Research

The management of malignant struma ovarii involves a multi-disciplinary approach, with surgery being the primary treatment option.

Surgical treatment options vary, but unilateral salpingo-oophorectomy (USO) is often recommended for stage I disease, reserving more radical surgery for advanced disease 2, 3.
Histopathological risk-stratification is essential to identify patients who may benefit from adjuvant thyroid-targeting therapies, such as thyroidectomy and radio-active iodine ablation therapy 2, 4, 5.
Radioiodine therapy (RAI) may be considered in some cases, although its benefits are uncertain 3.
Suppression of TSH with levothyroxine may be given to some patients, particularly those with metastatic disease 5, 6.
Long-term follow-up is necessary to detect metastases or tumor recurrence, with serial serum thyroglobulin measurements and 131I scan 5, 6.

Different treatment approaches have been reported in the literature, including:

Pelvic surgery, total thyroidectomy, and radioactive iodine therapy, followed by TSH suppression therapy with levothyroxine 6.
Laparoscopic right ovariectomy, multiple biopsies, and subsequent total thyroidectomy and radioiodine (131I) ablation 4.
Complete right ovariectomy, histopathological examination, and subsequent total thyroidectomy, radioiodine ablation, and L-thyroxine TSH suppressive doses 5.

The prognosis for patients with malignant struma ovarii is generally good, with a high overall survival rate 2, 3.

The 5-year and 10-year overall survival rates have been reported to be 95.3% and 88.7%, respectively 3.
However, the recurrent rate is relatively high, with 27.1% and 35.2% of patients experiencing recurrence at 5 and 10 years, respectively 3.