Breast cancer metastasis to the orbits is rare, accounting for 0.7% of all breast cancer cases. Out of all metastatic cancers to the orbit, breast cancer accounts for 50% of cases. Orbital metastasis at initial presentation is uncommon and the average time interval from initial breast cancer diagnosis to the development of orbital metastasis is 8.5 years. Prognosis is poor, with an average survival of 2-34 months.

A 59-year-old female with poorly differentiated ER/PR positive HER2/neu low breast cancer on Enhertu for 2 years with known metastases to the liver, mediastinum, peritoneum, spine s/p radiotherapy, PE/DVT, hemorrhagic gastritis presented with bilateral retro-orbital headache and worsening diplopia for 18 months. She had locally advanced left breast cancer in 1999 with 19/25 positive lymph nodes and underwent mastectomy, adjuvant chemotherapy, radiation and Zoladex with complete remission until 2021. Then, a suspicious left orbital tumor was discovered while on letrozole and palbociclib. Neurological exam demonstrated complete ophthalmoplegia in left eye and partial ophthalmoplegia in the right eye. MRI orbit demonstrated significantly increased enlargement and hyperenhancement of bilateral extraocular muscles, new in the right orbit with perineural enhancement of the optic nerve. MRI brain demonstrated new smooth dural enhancement without focal mass. CSF analysis was grossly unremarkable, and cytology did not grow any malignant cells.

Although breast cancer orbital metastasis is exceedingly rare, this diagnosis must be considered in a patient presenting with ocular symptoms in the setting of even remote breast cancer history. The aim of this case report is to demonstrate the extensive and devastating metastatic breast cancer involvement of bilateral orbits.