Endocrine Abstracts

Case history: A 67-year-old lady was referred to an endocrinologist for autoimmune hypothyroidism diagnosed in 2004. A treatment combination of levothyroxine and liothyronine was used. She had a history of recurrent metastatic ER-positive HER-2 negative lobular breast cancer with liver and bony metastatic involvement. She commenced with Letrozole (aromatase inhibitor) and Palbociclib (CDK inhibitor), later Fulvestrant (antioestrogen) and Crizotinib (tyrosine kinase inhibitor). The patient is on Capecitabine and Denosumab at the moment. She has not been on immunotherapy or checkpoint inhibitors at any time. From April 2020 the patient had what was thought to be progressively worsening thyroid eye disease (TED) with diplopia and exophthalmos. She had bilateral red and uncomfortable eyes, blurred vision and the patient developed a corneal ulcer in one eye. Ocular motility was reduced in all directions. The Clinical Activity Score for TED was 3 out of 7. Both MRI and CT scan of orbits described the picture being most likely secondary to severe TED with muscle enlargement. She received three intravenous infusions of methylprednisolone and rituximab in week two. In February 2021 an orbital biopsy was taken which showed metastatic disease secondary to breast cancer. The patient is scheduled for orbital radiotherapy to prevent a further compression of the optic nerve going forward as well as increasing proptosis.

Investigations: TSH 0,87 mU/l (0,3–4,2); fT4 17,1 pmol/l (9,00–19,00); fT3 4,7 pmol/l (2,60–5,70). Thyroid antibodies negative, TR-Ab negative. CT orbits: marked enlargement of the extraocular muscles bilaterally sparing the left superior oblique. Thought most likely to be secondary to severe TED. MRI orbita: Pattern of bilateral extraocular involvement with sparing of anterior tendon insertions, which is common finding in TED.

Results, treatment: The histology report from the orbital biopsy confirmed metastatic breast cancer involving the orbit. Treatment for autoimmune thyroid disease: levothyroxine 100 mcg four times altering 50 mcg three times a week, liothyronine 5mg twice a day. Treatment plan for orbitopathy: orbital radiotherapy to prevent further optic nerve compression. Treatment for metastatic breast cancer: continuing chemotherapy.

Conclusions, points for discussion: This case illustrates the challenges in patients with autoimmune thyroid disease and breast cancer. This is a rare association. To our knowledge, there are 3 reports in the ophthalmic literature. Breast cancer is the most common tumour to metastasize to the eye. Extraocular muscle metastases are uncommon, representing about 9% of orbital metastases, with bilateral presentation in up to 20% of cases.