Thyroid Hürthle Cell Carcinoma Metastatic to the Pituitary Gland

Dear Editor:

We read with interest the article by Vianello et al. in Thyroid (1), describing a patient with a follicular thyroid carcinoma metastasis to the pituitary gland causing pituitary insufficiency. The authors report this rare occurrence, and discuss the role of a treatment plan consisting of limited resection followed by multiple treatments with recombinant human thyrotropin followed by ¹³¹I. We would like to report a patient with Hürthle cell carcinoma (HCC) metastatic to the pituitary gland causing pituitary insufficiency and visual compromise. HCC requires a more extensive surgical resection given the pathology's relative resistance to other treatment modalities (2). To the best of our knowledge, a HCC metastasis causing pituitary insufficiency has not been previously reported.

A 75-year-old man with a history of HCC presented with lethargy. Twenty-one years before the current presentation, he underwent a thyroidectomy followed by radioactive iodine therapy for primary HCC. Ten years before the current presentation, he underwent a left upper lobe resection for a pulmonary HCC metastasis, and this recurred, requiring a second pulmonary resection 4 years later. Four years before the current presentation, he underwent a left adrenalectomy for an adrenal HCC metastasis. The patient's endocrinologic function was closely followed over his disease course. At the current presentation, the patient was found to have new onset abnormally low serum cortisol and serum testosterone. He was treated with hormone replacement therapy.

The patient then reported trouble with his vision, and formal testing demonstrated a dense bitemporal hemianopsia (see Supplementary Data, available online at www.liebertonline.com/thy). Subsequent magnetic resonance imaging of the brain showed an enhancing sellar mass with suprasellar extension and displacement of the optic chiasm (see Supplementary Data). The patient underwent an expanded endonasal endoscopic transsphenoidal resection of his tumor. At surgery, his optic chiasm was identified and decompressed. Pathologic specimens were consistent with HCC (see Supplementary Data). The patient had a routine postoperative course and remained on his hormone replacement therapy. He underwent fractionated external beam radiation to his cavity as an outpatient beginning on postoperative day number 10. On formal testing at 1 month, the patient's visual fields had greatly improved with only a mild bilateral peripheral deficit remaining.

Metastatic HCC to the pituitary gland has not previously been reported. In this instance, it presented with hypopituitarism and visual compromise. HCC metastatic lesions can be firm and vascular, making them more challenging to resect; however, given their relative resistance to adjuvant treatments, aggressive surgical removal remains a frontline therapy. Certainly, in most cases of visual compromise, operative decompression of the optic chiasm is warranted for the preservation of vision. In the present patient, the tumor was adherent to the surrounding tissues and, thus, the likelihood of residual disease was felt to be high; for this reason, he underwent postoperative external beam radiotherapy. When treating metastatic lesions in the pituitary fossa, it is important to understand the differences in the varying carcinomas originating from the thyroid gland, as different pathologies require different treatment regimens.