Cutaneous Melanoma with Metastasis to the Lateral Rectus Muscle

Abstract

A 47-year-old White man with metastatic cutaneous melanoma developed limited abduction in the right eye. An axial T2 fat-saturated magnetic resonance imaging (Fig A) revealed a heterogeneous right lateral rectus mass with mass effect on the optic nerve. There were no radiographic signs of globe tenting or exophthalmos. A skin biopsy from the patient’s back (Fig B) revealed large mononuclear cells with high nuclear-to-cytoplasm ratios, abundant mitotic figures, and that were positive for SOX-10. One week after Nivolumab, the patient developed compressive optic neuropathy.