Minimally invasive follicular thyroid carcinoma mimicking pituitary adenoma: a case report.

The metastasis of cancer to the pituitary gland is uncommon but may mimic a typical pituitary adenoma. Such cancers often derive from the breasts or the lungs, or very rarely from thyroid carcinoma. We described the case of a 60-year-old woman who presented with headaches and pain to the right eye. CT and MRI scans of the head revealed a sellar mass compressing the optic chiasm and invading the cavernous sinus. Her serum prolactin level was 1720 mIU/L. The preoperative diagnosis was pituitary adenoma. An endoscopic endonasal transsphenoidal approach was used to remove the tumor. Immunohistochemistry revealed immunoreactivity for thyroid transcription factor-1, CK-7, TG, supporting the diagnosis of a metastatic thyroid carcinoma. The rechecked thyroid ultrasonography showed a nodus with calcification on the left side. A total thyroidectomy was performed with a final histopathological diagnosis of minimally invasive follicular thyroid carcinoma. She was advised to take 131I treatment. The relevant literature is reviewed in light of this unusual case, illustrating the problems in the diagnosis and management of this type of patient.