Pituitary metastases of Hürthle cell carcinoma of the thyroid

Abstract

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.

Keywords: pituitary disorders; thyroid disease.

Figure 1

These are coronal (top row) and sagittal (bottom row) slices of T1-weighted images taken from serial MRI scans of the pituitary with contrast and arrowheads showing the lesion. At diagnosis (A and D), the intrasellar component of the enhancing pituitary mass measured 13×11 mm and was causing deviation of the pituitary stalk and extension into the right cavernous sinus, but with no direct infiltration. Six months later (B and E), the intrasellar component had increased in size to 21×15 mm, with deviation of the pituitary stalk and optic chiasm. There is also further extension into the right cavernous sinus and early left cavernous sinus involvement with inferior extension into the sphenoid sinus and clivus. Four months later and preoperation (C and F), the intrasellar component was 26×21 mm and there is elevation of the chiasm.

Figure 2

Coronal (top row) and sagittal (bottom row) slices of T1-weighted images taken from serial MRI pituitary with contrast and arrowheads showing the lesion. The immediate preoperative images (A and C) are shown on the left (as seen in figure 1) and these can be compared with the 5-month postoperative images (B and D) on the right, which show good debulking of the tumour with persistent small enhancing foci, which may represent post-radiotherapy effect; however, residual tumour cannot be entirely excluded.

Figure 3

Light microscopy: (A) H&E slide showing sheets of tumour cells forming occasional follicles. The tumour cells have irregular nuclei, occasional prominent nucleoli and abundant granular, eosinophilic cytoplasm; ×20; (B–D) immunohistochemistry shows that there is widespread tumorous expression of paired box gene 8 (B), thyroid transcription factor-1 (C) and thyroglobulin (D); ×20.