Occult papillary thyroid carcinoma metastasis to the sacrum and the skull: an unusual presentation.

This case represents occult follicular variant of papillary thyroid carcinoma (FVPTC) with large metastasis to the sacrum. The patient, a 42-year-old female, presented after hemithyroidectomy for benign follicular adenoma with lower back pain associated with fever and sweating. A lytic lesion of the left sacral bone was found on the CT with biopsy showing metastatic carcinoma with morphology and immunophenotype of thyroid gland primary tumor proven to be FVPTC. The patient had completion thyroidectomy with benign pathology.