Unusual Widespread Metastatic Presentation of Mixed Medullary–Follicular Thyroid Carcinoma

Mixed medullary–follicular thyroid carcinoma (MMFTC) is a rare tumor with a metastatic behavior that has not been fully appreciated. Scintigraphy and radioiodine entrapment propensity of its metastases remains largely undescribed. The authors present a case of MMFTC with widespread bone and soft-tissue metastases, where every known site of metastases concentrated radioiodine intensely. The patient responded well to radioiodine therapy. The report suggests that the tumor may have a propensity to metastasize to the skeleton, and the metastases retain the ability to accumulate radioiodine.