Pituitary metastases of Hürthle cell carcinoma of the thyroid.

An 85-year-old man was referred to endocrinology following the discovery of an incidental pituitary mass on cranial imaging which was thought to be a non-functioning adenoma during an admission with headaches, lethargy, confusion and hyponatraemia. He had a history of Hürthle cell carcinoma of the thyroid treated with total thyroidectomy, ablative radioiodine therapy and thyroxine replacement. Subsequently, he developed metastatic spread to the neck, lungs and skeleton. About 9 months later, the patient had deterioration of vision. MRI showed a rapidly expanding pituitary mass with compression of the optic chiasm. Biochemical investigations confirmed hypocortisolism and hypogonadism. The patient underwent trans-sphenoidal resection of the pituitary mass followed by external beam radiotherapy to the pituitary bed. Histopathology confirmed a metastatic deposit of Hürthle cell carcinoma, which is a rare and aggressive variant of follicular thyroid carcinoma.