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 mlU/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 I-131 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.