Case: We report the case of a 38-year-old woman who presented with a lytic bone lesion in the left scapula. A biopsy showed a tumor with the histologic appearance of thyroid tissue. She also was found to have a thyroid nodule and an enlarged ovary, both of which were excised. The thyroid nodule turned out to be a benign colloid nodule, and the ovary contained a monodermal teratoma composed of thyroid tissue (struma ovarii). The lesion in the scapula eventually was proven to be metastatic malignant struma ovarii.
Conclusion: Malignant struma ovarii with bone metastases is very rare, and its diagnosis is a challenge. There are some documented cases with bone metastases, mostly to the thoracic and lumbar spine. The optimal treatment of choice for the bone lesion is unknown because of the rarity of its presentation.