Unilateral, Sectoral Retinal Metastasis of Small-Cell Lung Cancer Mimicking Viral Retinitis.

PURPOSE: To report a case of unilateral, sectoral retinal metastasis of small-cell lung cancer (SCLC) that mimicked cytomegalovirus (CMV) retinitis. METHOD: Case report. RESULTS: A 48-year-old woman presented with a four-week history of a visual field loss in her right eye. She had a past medical history of extensive-stage SCLC with brain metastasis, stable on maintenance atezolizumab for two years. On initial presentation, she was diagnosed with CMV retinitis. No improvement was observed with 4 weeks of oral valganciclovir. Upon referral for a second opinion, her fundus exam appeared compatible with CMV retinitis, and anterior chamber tap for polymerase chain reaction for viral etiologies was performed followed by intravitreal and intravenous ganciclovir without improvement. She was referred for a third opinion, where diagnostic vitrectomy with vitreous and retinal biopsies were consistent with SCLC metastatic to the retina. The patient underwent enucleation of the right eye for definitive pathologic analysis and subsequently was started on additional systemic chemotherapy. CONCLUSION: Retinal metastases are exceedingly rare, particularly retinal metastasis of SCLC. Retinal metastasis should be considered in patients initially diagnosed with viral retinitis who fail to improve despite antiviral therapy, particularly if they have a known history of malignancy. Furthermore, retinal metastasis of SCLC potentially could be misdiagnosed histopathologically as retinoblastoma if the patient's history is unknown and appropriate immunohistochemical stains are not performed.