Isolated optic nerve metastasis of breast cancer initially mimicking retrobulbar optic neuritis

Purpose. To report a pathologically confirmed case of optic nerve metastasis of breast carcinoma, which was initially misdiagnosed as a retrobulbar optic neuritis. There have been no case reports of isolated optic nerve metastasis of breast carcinoma with nonspecific initial fundus and neuroimaging findings. Methods. A 51-year-old woman presented with decreased visual acuity in her left eye for 15 days. She had undergone a left modified radical mastectomy 10 years earlier. The funduscopic findings were nonspecific, except for a slightly enlarged cup-to-disc ratio of 0.6 in both eyes. The brain magnetic resonance imaging (MRI) findings were nonspecific and cerebrospinal fluid (CSF) findings were also nonspecific and negative for malignant cells. Therefore, she was diagnosed with idiopathic retrobulbar optic neuritis rather than metastasis of breast carcinoma. Intravenous steroid pulse therapy was given for 3 days. Results. The left visual acuity decreased gradually, and after 2 months was light perception-negative in the left eye. Fundus findings and CSF study results were also nonspecific as the initial presentation. On the subsequent orbit MRI, diffuse enlargement and an enhancing segment of the left optic nerve was observed, which suggested metastasis to the left optic nerve. A craniotomy and biopsy of the left optic nerve was performed. The pathologic results revealed metastatic invasive ductal carcinoma of the breast. She underwent Cyberknife surgery followed by systemic chemotherapy. Conclusions. Patients with known cancer at another site of the body who develop optic neuropathy, with or without evidence of metastasis, should be suspected to have cancer as a cause.