"Malignant struma ovarii" with peritoneal metastasis: report of two cases.

Malignant struma ovarii with metastasis in an extremely rare form of ovarian carcinoma. We describe two cases of malignant struma ovarii that demonstrated widespread peritoneal metastases. In the second case described here, furthermore, the tumor recurred II years later in the contralateral ovary and omentum, while the primary tumor previously was pure struma ovarii with no evidence of metastasis. Although thyroid tumors themselves are characterized by a long latent interval, patients with benign thyroid tissue arising in nonthyroidal organs with or even without dissemination should be managed with caution and need appropriate long-term follow-up after the initial surgery.