The White Caruncle: Sign of a Keratinous Cyst Arising From a Sebaceous Gland DuctJakobiec, Frederick A MD, DSc; Mehta, Manisha MD; Greenstein, Scott H MD; Colby, Kathryn MD, PhDCornea: April 2010 - Volume 29 - Issue 4 - p 453-455 doi: 10.1097/ICO.0b013e3181b55b5c Case Report Abstract Author Information Purpose: To describe an acquired, smooth white lesion of the caruncle and to underscore the role of subsurface keratinizing squamous epithelium in its formation. Methods: Clinical photographic documentation, histopathologic evaluation, and immunohistochemical staining of an excised specimen from a 25-year-old woman. Results: A cyst was found that was lined by keratinizing squamous epithelium without a keratohyaline layer (trichilemmal keratinization), typical of lesions of the pilosebaceous unit. A portion of the cyst's lining was replaced by granulomatous inflammation resulting from an earlier spontaneous partial rupture. Ki-67 immunolabeling demonstrated relatively few nuclei in S-phase (DNA synthesis) in comparison with the overlying epithelium, thereby suggesting an obstructive, nonproliferative cause for the cyst. Conclusion: A white caruncular lesion is a very rare finding according to the literature. It is most likely caused by a cyst lined by squamous epithelium elaborating trichilemmal-type keratin. A sebaceous gland duct was established as the source for the current lesion. From the *Department of Ophthalmology; †David G. Cogan Laboratory of Ophthalmic Pathology; ‡Comprehensive Ophthalmology Service; and §Cornea Service, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA. Received for publication May 29, 2009; accepted June 17, 2009. Reprints: Frederick A. Jakobiec, MD, DSc, Director, David G. Cogan Laboratory of Ophthalmic Pathology, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114 (e-mail: Fred_Jakobiec@meei.harvard.edu). Copyright © 2010 Wolters Kluwer Health, Inc. All rights reserved.