Biopsy-Proven Metastatic Merkel Cell Carcinoma to the Orbit: Case Report and Review of Literature

Merkel cell carcinoma is a rare neuroendocrine tumor of subspecialized dermal mechanoreceptors, associated with immunosuppression. The usual ophthalmic presentation is an eyelid lesion. The authors present a case of biopsy-proven orbital metastatic Merkel cell carcinoma in the absence of any eyelid lesion, in an immunosuppressed patient with a history of multiple cancers. There are to the authors' knowledge only 2 other case reports of presumed metastatic Merkel cell carcinoma to the orbit, though neither were biopsied. Despite its rarity, metastatic Merkel cell carcinoma should be included in the differential of a metastatic orbital lesion, in the patient with a known or suspected cutaneous primary. The patient has had an excellent response to combined radiotherapy and programmed death-1 inhibitor pembrolizumab, and this case highlights the potential benefit of an exciting new biologic therapy. Accepted for publication December 15, 2017. The authors have no financial or conflicts of interest to disclose. Address correspondence and reprint requests to Dean R. Cugley, M.B.B.S.(Hons), B.Med.Sci., Royal Victorian Eye & Ear Hospital, 32 Gisborne Street, East Melbourne, VIC 3002, Australia. E-mail: dean.cugley@eyeandear.org.au © 2018 by The American Society of Ophthalmic Plastic and Reconstructive Surgery, Inc., All rights reserved.