Elevation of serum tumor marker CA 15.3 levels as the first manifestation of metastatic breast cancer to the cavernous sinus.

We report rising tumor marker levels of CA 15.3 as the presenting manifestation of metastatic breast cancer to the cavernous sinus and orbit. A 39-year-old woman with a history of breast cancer developed increasing levels of tumor marker CA15.3. Ten months later, she developed vision loss in the right eye, diplopia, and right-sided ptosis. A magnetic resonance scan of the head showed a mass involving the right cavernous sinus and superior orbital fissure. Biopsy of the lesion showed metastatic breast cancer. She was treated with surgery and radiotherapy and did well. Ophthalmologists should be aware of the significance of increasing levels of tumor markers, such as CA 15.3, in patients with a history of breast cancer and new neuroophthalmologic signs or symptoms.