Thyroid carcinoma arising from a sacrococcygeal mass: a malignant teratoma?

A 59-year-old African American male with a remote history of Graves' disease presented with a 13-cm sacrococcygeal mass that was resected. Pathologic examination revealed this to be papillary thyroid carcinoma with large areas of hemorrhage and necrosis. No other teratomatous elements were identified. The patient underwent extensive evaluation of the thyroid gland with ultrasound, computed tomography (CT) scan, and laboratory studies without any evidence of thyroid mass or malignancy. In addition, further evaluations with chest/abdominal/pelvic CT as well as a bone scan failed to reveal any evidence of metastatic disease. At 1-year follow-up, the patient has remained euthyroid and without evidence of recurrence. We believe that our patient may represent the first reported case of malignant transformation of mature thyroid tissue in a sacrococcygeal teratoma. The impact of his diagnosis on the decision-making for performing a total thyroidectomy is discussed.