Tall cell papillary thyroid carcinoma metastatic to femur: Evidence for thyroid hormone synthesis within the femur

A 67-year old man with a 3-month history of left hip pain had a history of Graves disease, treated with I-131 20 years before admission, and papillary thyroid carcinoma, treated with cervical lymphadenopathy 9 years before ad mission. Removal of a 3.5- x 5-cm mass from the left femur revealed it to b e a tall cell variant of papillary thyroid carcinoma. Removal of this mass resulted in his thyrotropin level increasing from 2 (presurgery) to 23 mlU/ mL, whereas his thyroxine level simultaneously decreased from 5.79 (presurg ery) to 2.29 mug/dL 12 days after surgery despite continuation of levothyro xine of 0.137 mg/day. On histological examination, the tall cell variant in the femur was producing abundant thyroglobulin. This first case of a metas tatic papillary thyroid carcinoma in bone producing thyroid hormone to the extent that the patient became hypothyroid after removal of this metastasis illustrates that metastatic thyroid lesion(s) may produce significant amou nts of thyroid hormone.