Pituitary Metastases from Follicular Thyroid Carcinoma

Abstract

Metastatic carcinomas to the pituitary gland are uncommon, occurring in only 1% of the pituitary masses. They often originate from breast or lung carcinomas and may resemble a nonfunctioning pituitary adenoma both clinically and radiologically. Here we describe a patient with pituitary metastasis from follicular thyroid carcinoma and discuss the unique features of these lesions. A 45-year-old woman was admitted to the emergency rescue room of our hospital with a 2-month history of progressive headache and blurred vision. Evaluation revealed right eye amaurosis, with a mild abducens and oculomotor palsy. Pituitary magnetic resonance imaging showed a mass that was hypo-intense in T1-weighted and hyper-intense in T2-weighted-images, located from the sphenoid sinus up to chiasmatic cisterns, raising and deflecting the optic chiasm, down to hypopharynx region, and distorting the cavernous sinuses. No evidence of anterior or posterior hypopituitarism was recorded. The immediate trans-sphenoidal surgery was uncomplicated with partial improvement of the visual fields and headache. Histopathology revealed a metastasis with well-differentiated follicular thyroid architecture. Total thyroidectomy and lymph node dissection was performed with a final histopathological diagnosis of follicular thyroid carcinoma. Subsequently, her headache became more severe. 131-I ablation treatments were performed 15 days and 12 months after thyroidectomy with decrease in headache and a decline in serum thyroglobulin levels. Pituitary metastases from thyroid carcinoma are very uncommon. As this patient illustrates, they tend to produce symptoms relating to space-occupying expansion in the parasellar region rather than to those due to destruction of the pituitary gland. Although rare, pituitary metastases caused by thyroid malignancy should be considered in patients with expanding parasellar lesions if they have thyroid cancer or uncharacterized thyroid diseases. They are unlikely to be amenable to complete resection and should be considered for 131-I treatment, perhaps avoiding the need for extensive neurological surgery.